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Evaluation of preventive,supportive and awareness building measures among international students in China in response to COVID-19:a structural equation modeling approach

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Global Health Research and Policy 2021年第1期6卷 404-413页

作者： Tanwne Sarker Apurbo Sarkar md.ghulam rabbany Milon Barmon Rana Roy md.Ashfikur Rahman Kh.Zulfikar Hossain Fazlul Hoque Muhammad Asaduzzaman School of Economics and Finance Xi’an Jiaotong UniversityXi’anShaanxi 710049People’s Republic of China College of economics and management Northwest A&F UniversityYanglingShaanxi 712100People’s Republic of China Department of agribusiness and marketing Sher-e-Bangla Agricultural UniversityDhaka 1207Bangladesh Institute of Soil and Water Conservation Northwest A&F UniversityYanglingShaanxi 712100People’s Republic of China College of Natural Resource and Environment Northwest A&F UniversityYanglingShaanxi 712100People’s Republic of China Department of Agroforestry&Environmental Science Sylhet Agricultural UniversitySylhet 3100Bangladesh Centre for Global Health University of OsloKirkeveien 166Frederik Holsts hus0450 OsloNorway

Background:Education institutions promptly implemented a set of steps to prevent the spread of COVID-19 among international Chinese students,such as restrictive physical exercise,mask wear,daily health reporting,*** of such behavioral change campaigns largely depends on awareness building,satisfaction and trust on the *** purpose of this current study is to assess the preventive,supportive and awareness-building steps taken during the COVID-19 pandemic for international students in China,that will be useful for planning such a behavioral change campaign in the potential pandemic situation in other parts of the ***:We conducted an online-based e-questionnaire survey among 467 international students in China through *** data collection duration was from February 20,2020 to March 10,2020 and we focused on their level of awareness,satisfaction,and trust in authorities regarding pandemic *** bivariate statistics was used to describe the background characteristics of the respondents along with adoption of the partial least squares-structural equation modeling(PLS-SEM)as the final model to demonstrate the relationship between the ***:In our study,the leading group of the respondents were within 31 to 35 years’age group(39.82%),male(61.88%),living single(58.24%)and doctoral level students(39.8%).The preventive and supportive measures taken by students and/or provided by the respective institution or authorities were positively related to students’satisfaction and had an acceptable strength(β=0.611,t=9.679,p<0.001).The trust gained in authorities also showed an acceptable strength(β=0.381,t=5.653,p<0.001)with a positive ***,the personnel awareness building related to both students’satisfaction(β=0.295,t=2.719,p<0.001)and trust gain(β=0.131,t=1.986,p<0.05)in authorities had a positive and acceptable ***,our study clearly demonstrates the great impact of preventive and supportive measure

关键词： COVID-19 Awareness building Epidemic PLS-SEM Supportive measures Trust international student modeling

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Sugarcane bagasse amendment mitigates nutrient leaching from a mineral soil under tropical conditions

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Pedosphere 2022年第6期32卷 876-883页

作者： Nan XU Jehangir H.BHADHA Abul rabbany Stewart SWANSON James MMCCRAY Yuncong LI Sarah LSTRAUSS Rao MYLAVARAPU Horticultural Sciences Department University of FloridaGainesville FL 32611(USA) Everglades Research and Education Center University of FloridaBelle Glade FL 33430(USA) Department of Soil Waterand Ecosystem SciencesUniversity of FloridaGainesville FL 32611(USA) Institute of Food and Agricultural Sciences(IFAS)Extension University of FloridaLaBelle FL 33935(USA) Agronomy Department University of FloridaBelle Glade FL 33430(USA) Department of Soil Waterand Ecosystem SciencesUniversity of FloridaHomestead FL 33031(USA) Department of Soil Waterand Ecosystem SciencesUniversity of FloridaImmokalee FL 34142(USA)

Large quantities of organic by-products are generated by the sugarcane industry during sugar extraction *** by-products may be used as soil amendments to improve soil quality,as nutrient leaching is common in mineral soils of Florida in USA due to their sandy texture and frequent rain events.A soil column study was designed to evaluate the effects of bagasse application at 85 t ha^(-1) of fresh bagasse,170 t ha^(-1) of fresh bagasse,and 170 t ha^(-1) of fresh bagasse+nitrogen(N)on the leaching potential of carbon(C),N,phosphorus(P),and potassium(K).Bagasse was incorporated within the topsoil(0-15 cm)in outdoor soil columns exposed to natural conditions,with periodical irrigation during the *** approximately 57 weeks,the distributions of C,N,P,and K were evaluated at three soil depths(i.e.,0-15,15-30,and 30-53 cm)within the soil *** organic C(TOC),N,and P in leachates decreased significantly from the soils amended with bagasse compared with the control with no bagasse and no *** on K content changes in the columns,bagasse could also be utilized as a potential source of K for ***,application of bagasse as a soil amendment might be an effective way to sustainably reutilize organic by-products while reducing concerns regarding major nutrients entering groundwater *** results of this study could assist in developing nutrient management plans of using sugarcane bagasse as a potential soil amendment in mineral soils.

关键词： nutrient leaching potential nutrient loss pore volume sandy soil soil amendment soil column sugarcane by-product

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Improved Between-Satellite Single-Difference Precise Point Positioning Model Using Triple GNSS Constellations: GPS, Galileo, and BeiDou

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Positioning 2016年第2期7卷 63-74页

作者： Akram Afifi Ahmed El-rabbany Department of Civil Engineering Ryerson University Toronto Canada

This paper introduces a new dual-frequency precise point positioning (PPP) model, which combines the observations of three different GNSS constellations, namely GPS, Galileo, and BeiDou. Our model is based on between-satellite single-difference (BSSD) linear combination, which cancels out some receiver-related biases, including receiver clock error and non-zero initial phase bias of the receiver oscillator. The reference satellite can be selected from any satellite system GPS, Galileo, and BeiDou when forming BSSD linear combinations. Natural Resources Canada’s GPS Pace PPP software is modified to enable a combined GPS, Galileo, and BeiDou PPP solution and to handle the newly introduced biases. A total of four data sets at four IGS stations are processed to verify the developed PPP model. Precise satellite orbit and clock products from the IGS-MGEX network are used to correct both of the GPS and Galileo measurements. It is shown that using the BSSD linear combinations improves the precision of the estimated parameters by about 25% compared with the GPS-only PPP solution. Additionally, the solution convergence time is reduced to 10 minutes for both BSSD scenarios, which represent about 50% improvement in comparison with the GPS-only PPP solution.

关键词： PPP BSSD GPS Galileo BeiDou

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PPP Accuracy Enhancement Using GPS/GLONASS Observations in Kinematic Mode

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Positioning 2015年第1期6卷 1-6页

作者： Mahmoud Abd Rabbou Ahmed El-rabbany Department of Civil Engineering Ryerson University Toronto Canada

Commonly, kinematic PPP techniques employ un-differenced ionosphere-free linear combination of GPS observations. This, however, may not provide continuous solution in urban areas as a result of limited satellite visibility. In this paper, the traditional un-differenced as well as between-satellite single-difference (BSSD) ionosphere-free linear combinations of GPS and GLONASS measurements are developed. Except GLONASS satellite clock products, the final precise GPS and GLONASS satellites clock and orbital products obtained from the multi-GNSS experiment (MGEX) are used. The effects of ocean loading, earth tide, carrier-phase windup, sagnac, relativity, and satellite and receiver antenna phase-center variations are rigorously modeled. Extended Kalman filter (EKF) is developed to process the combined GPS/GLONASS measurements. A comparison is made between three kinematic PPP solutions, namely standalone GPS, standalone GLONASS, and combined GPS/ GLONASS solutions. In general, the results indicate that the addition of GLONASS observations improves the kinematic positioning accuracy in comparison with the standalone GPS PPP positioning accuracy. In addition, BSSD solution is found to be superior to that of the traditional un-diffe- renced model.

关键词： GPS GLONASS PPP Kalman Filter (KF)

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Real-Time GPS/Galileo Precise Point Positioning Using NAVCAST Real-Time Corrections

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Positioning 2019年第3期10卷 35-49页

作者： Abdelsatar Elmezayen Ahmed El-rabbany Department of Civil Engineering Ryerson University Toronto Canada

Real-time precise point positioning (PPP) is possible through the use of real-time precise satellite orbit and clock corrections, which are available through a number of organizations including the International GNSS Service (IGS) real-time service (IGS-RTS). Unfortunately, IGS-RTS is only available for the GPS and GLONASS constellations. In 2018, a new real-time service, NAVCAST, which provides real-time precise orbit and clock corrections for the GPS and Galileo constellations, was launched. In this research, the potential performance of real-time PPP which makes use of NAVCAST real-time corrections is analyzed using various static and kinematic datasets. In the static dataset, 24 hours of observations from eight IGS stations in Canada over three different days were utilized. The static results show that the contribution of Galileo satellites can improve the positioning accuracy, with 30%, 34%, and 31% in east, north, and up directions compared to the GPS-only counterparts. In addition, centimeter-level positioning accuracy in the horizontal direction and decimeter-level positioning accuracy in the vertical direction can be achieved by adding Galileo observations. In the kinematic dataset, a real vehicular test was conducted in urban and suburban combined areas. The real-time kinematic GPS/Galileo PPP solutions demonstrate an improvement of about 53%, 45%, and 70% in east, north, and up directions compared to the GPS-only counterparts. It is shown that the real-time GPS/Galileo PPP can achieve a sub-decimeter horizontal positioning accuracy and about meter-level vertical positioning accuracy through the use of NAVCAST real-time corrections.

关键词： NAVCAST Static Kinematic GPS/Galileo PPP

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Integration of Multi-Constellation GNSS Precise Point Positioning and MEMS-Based Inertial Systems Using Tightly Coupled Mechanization

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Positioning 2015年第4期6卷 81-95页

作者： Mahmoud Abd Rabbou Ahmed El-rabbany Department of Civil Engineering Ryerson University Toronto Canada

We develop a new integrated navigation system, which integrates multi-constellations GNSS precise point positioning (PPP), including GPS, GLONASS and Galileo, with low-cost micro-electro-mechanical sensor (MEMS) inertial system, for precise positioning applications. To integrate GNSS and the MEMS-based inertial system, the process and measurement models are developed. Tightly coupled mechanism is adopted, which is carried out in the GNSS raw measurements domain. Both un-differenced and between-satellite single-difference (BSSD) ionosphere-free linear combinations of pseudorange and carrier phase GNSS measurements are processed. Rigorous models are employed to correct GNSS errors and biases. The GNSS inter-system biases are considered as additional unknowns in the integrated error state vector. The developed stochastic model for inertial sensors errors and biases are defined based on first order Gaussian Markov process. Extended Kalman filter is developed to integrate GNSS and inertial measurements and estimate inertial measurements biases and errors. Two field experiments are executed, which represent different real-world scenarios in land-based navigation. The data are processed by using our developed Ryerson PPP GNSS/MEMS software. The results indicate that the proposed integrated system achieves decimeter to centimeter level positioning accuracy when the measurement updates from GNSS are available. During complete GNSS outages the developed integrated system continues to achieve decimeter level accuracy for up to 30 seconds while it achieves meter-level accuracy when a 60-second outage is introduced.

关键词： GNSS GPS Galileo GLONASS MEMS PPP Tightly Coupled

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Monocular VO Scale Ambiguity Resolution Using an Ultra Low-Cost Spike Rangefinder

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Positioning 2020年第4期11卷 45-60页

作者： Ahmed El Amin Ahmed El-rabbany Department of Civil Engineering Ryerson University Toronto Canada

Monocular visual odometry (VO) is the process of determining a user’s trajectory through a series of consecutive images taken by a single camera. A major problem that affects the accuracy of monocular visual odometry, however, is the scale ambiguity. This research proposes an innovative augmentation technique, which resolves the scale ambiguity problem of monocular visual odometry. The proposed technique augments the camera images with range measurements taken by an ultra-low-cost laser device known as the Spike. The size of the Spike laser rangefinder is small and can be mounted on a smartphone. Two datasets were collected along precisely surveyed tracks, both outdoor and indoor, to assess the effectiveness of the proposed technique. The coordinates of both tracks were determined using a total station to serve as a ground truth. In order to calibrate the smartphone’s camera, seven images of a checkerboard were taken from different positions and angles and then processed using a MATLAB-based camera calibration toolbox. Subsequently, the speeded-up robust features (SURF) method was used for image feature detection and matching. The random sample consensus (RANSAC) algorithm was then used to remove the outliers in the matched points between the sequential images. The relative orientation and translation between the frames were computed and then scaled using the spike measurements in order to obtain the scaled trajectory. Subsequently, the obtained scaled trajectory was used to construct the surrounding scene using the structure from motion (SfM) technique. Finally, both of the computed camera trajectory and the constructed scene were compared with ground truth. It is shown that the proposed technique allows for achieving centimeter-level accuracy in monocular VO scale recovery, which in turn leads to an enhanced mapping accuracy.

关键词： Spike Visual Odometry Monocular Scale

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An Improved Model for Single-Frequency GPS/GALILEO Precise Point Positioning

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Positioning 2015年第2期6卷 7-21页

作者： Akram Afifi Ahmed El-rabbany Department of Civil Engineering Ryerson University Toronto Canada

This paper introduces a new precise point positioning (PPP) model, which combines single-fre- quency GPS/Galileo observations in between-satellite single-difference (BSSD) mode. In the absence of multipath, all receiver-related errors and biases are cancelled out when forming BSSD for a specific constellation. This leaves the satellite originating errors and atmospheric delays un- modelled. Combining GPS and Galileo observables introduces additional biases that have to be modelled, including the GPS to Galileo time offset (GGTO) and the inter-system bias. This paper models all PPP errors rigorously to improve the single-frequency GPS/Galileo PPP solution. GPSPace PPP software of Natural Resources Canada (NRCan) is modified to enable a GPS/Galileo PPP solution and to handle the newly introduced biases. A total of 12 data sets representing the GPS/Galileo measurements of six IGS-MEGX stations are processed to verify the newly developed PPP model. Precise satellite orbit and clock corrections from IGS-MEGX networks are used for both GPS and Galileo measurements. It is shown that sub-decimeter level accuracy is possible with single-frequency GPS/Galileo PPP. In addition, the PPP solution convergence time is improved from approximately 100 minutes for the un-differenced single-frequency GPS/Galileo solution to approximately 65 minutes for the BSSD counterpart when a single reference satellite is used. Moreover, an improvement in the PPP solution convergence time of 35% and 15% is obtained when one and two reference satellites are used, respectively.

关键词： PPP GPS Galileo BSSD

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