Global Users Research Articles

Project AstroSat: Five Years of Operations and Continuing

India’s first dedicated multi-wavelength satellite, AstroSat, was launched by PSLV C30 from the Satish Dhawan Space Centre, Sriharikota, Andhra Pradesh on 28 September 2015. It is India’s first multiwavelength observatory. AstroSat carries five scientific payloads and is capable of simultaneous observations from ultraviolet to very hard X-rays. It has completed five years of on-board operations in September 2020 as a proposal-based observatory. Currently, it has close to 1500 global users and has resulted in more than 150 articles in peer-reviewed journals. This article is an overview providing a brief description of the AstroSat mission and some recent results using data from this unique Indian space observatory.

Vulnerability disclosure and cybersecurity awareness campaigns on twitter during COVID‐19

The COVID‐19 pandemic introduced the new norm that changed the way we work and live. During these unprecedented times, most of the organizations expected their employees to work from home. Remote working created new opportunities for hackers since more users were making use of digital platforms for online shopping, accessing Virtual Private Network (VPN), videoconferencing platforms, and software alike. Consequently, cybercrime increased due to the increase in the attack surface, and software vulnerabilities were exploited for launching cyberattacks. There is existing research that explores vulnerability disclosure on Twitter. However, there is a lack of study on opportunistic targeted attacks where specific vulnerabilities are exploited in a way that benefit adversaries the most in times such as COVID‐19. The primary aim of this work is to study the effectiveness of vulnerability disclosure pattern on Twitter in COVID‐19, and discuss how Twitter can be leveraged as Open‐Source Intelligence (OSINT) during a pandemic where the global users can follow a coordinated approach to share security‐related information and conduct awareness campaigns. The study identifies Twitter as an apt source for conducting cybersecurity awareness campaigns as 99.83% of the security vulnerabilities are found to be accurate. The information can help global cybersecurity agencies to proactively identify vulnerabilities, coordinate activities, and plan for mitigation strategies since releasing patches from the vendor might take time.

Discussion, news information, and research sharing on social media at the onset of Covid-19

Social media platforms provide valuable insights into public conversations. They likewise aid in understanding current issues and events. Twitter has become an important virtual venue where global users hold conversations, share information, and exchange news and research. This study investigates social network structures among Twitter users with regard to the Covid-19 outbreak at its onset and its spread. The data were derived from two Twitter datasets by using a search query, “coronavirus,” on February 28th, 2020, when the coronavirus outbreak was at a relatively early stage. The first dataset is a collection of tweets used in investigating social network structures and for visualization. The second dataset comprises tweets that have citations of scientific research publications regarding coronavirus. The collected data were analyzed to examine numerical indicators of the social network structures, subgroups, influencers, and features regarding research citations. This was also essential to measure the statistical relationships among social elements and research citations. The findings revealed that individuals tend to have conversations with specific people in clusters regarding daily issues on coronavirus without prominent or central voice tweeters. Tweets related to coronavirus were often associated with entertainment, politics, North Korea, and business. During their conversations, the users also responded to and mentioned the U.S. president, the World Health Organization (WHO), celebrities, and news channels. Meanwhile, people shared research articles about the outbreak, including its spread, symptoms related to the disease, and prevention strategies. These findings provide insight into the information sharing behaviors at the onset of the outbreak.

Enhanced Neural Network Model for Worldwide Estimation of Weighted Mean Temperature

Precise modeling of weighted mean temperature (Tm) is critical for realizing real-time conversion from zenith wet delay (ZWD) to precipitation water vapor (PWV) in Global Navigation Satellite System (GNSS) meteorology applications. The empirical Tm models developed by neural network techniques have been proved to have better performances on the global scale; they also have fewer model parameters and are thus easy to operate. This paper aims to further deepen the research of Tm modeling with the neural network, and expand the application scope of Tm models and provide global users with more solutions for the real-time acquisition of Tm. An enhanced neural network Tm model (ENNTm) has been developed with the radiosonde data distributed globally. Compared with other empirical models, the ENNTm has some advanced features in both model design and model performance, Firstly, the data for modeling cover the whole troposphere rather than just near the Earth’s surface; secondly, the ensemble learning was employed to weaken the impact of sample disturbance on model performance and elaborate data preprocessing, including up-sampling and down-sampling, which was adopted to achieve better model performance on the global scale; furthermore, the ENNTm was designed to meet the requirements of three different application conditions by providing three sets of model parameters, i.e., Tm estimating without measured meteorological elements, Tm estimating with only measured temperature and Tm estimating with both measured temperature and water vapor pressure. The validation work is carried out by using the radiosonde data of global distribution, and results show that the ENNTm has better performance compared with other competing models from different perspectives under the same application conditions, the proposed model expanded the application scope of Tm estimation and provided the global users with more choices in the applications of real-time GNSS-PWV retrival.

Caching-Aware Intelligent Handover Strategy for LEO Satellite Networks

Recently, many Low Earth Orbit (LEO) satellite networks are being implemented to provide seamless communication services for global users. Since the high mobility of LEO satellites, handover strategy has become one of the most important topics for LEO satellite systems. However, the limited on-board caching resource of satellites make it difficult to guarantee the handover performance. In this paper, we propose a multiple attributes decision handover strategy jointly considering three factors, which are caching capacity, remaining service time and the remaining idle channels of the satellites. Furthermore, a caching-aware intelligent handover strategy is given based on the deep reinforcement learning (DRL) to maximize the long-term benefits of the system. Compared with the traditional strategies, the proposed strategy reduces the handover failure rate by up to nearly 81% when the system caching occupancy reaches 90%, and it has a lower call blocking rate in high user arrival scenarios. Simulation results show that this strategy can effectively mitigate handover failure rate due to caching resource occupation, as well as flexibly allocate channel resources to reduce call blocking.

A novel fine Doppler frequency acquisition algorithm for BDS‐3 B1C signal based on an adaptive filter

Fine Doppler frequency estimation has an important role in accelerating the convergence of the tracking loop in a global navigation satellite system (GNSS) receiver to achieve short time to first fix. BDS-3 started broadcasting a civil B1C signal to provide open services for global users, which is beneficial for GNSS-based applications. Therefore, a fine Doppler frequency acquisition algorithm based on an adaptive filter is proposed, whose purpose is to acquire the BDS-3 B1C signal Doppler frequency accurately after the completion of coarse acquisition. The proposed algorithm is based on a first-order complex-coefficients adaptive filter. The adaptive filter depends on the proposed adaptation algorithm to track the input BDS-3 B1C signal. An accurate Doppler frequency estimate is extracted. Simulation results show the proposed algorithm has high acquisition sensitivity, high acquisition accuracy, short acquisition time, and few hardware resources consumption, and also works well under many different coarse acquisition strategies. Overall, the proposed algorithm is better than the generic second-order frequency locked loop. Consequently, the proposed algorithm has high practical value.

Influence of COVID-19 Lockdowns on the Usage of a Vision Assistance App Among Global Users With Visual Impairment: Big Data Analytics Study.

BackgroundMillions of individuals with visual impairment use vision assistance apps to help with their daily activities. The most widely used vision assistance apps are magnifier apps. It is still largely unknown what the apps are used for. Lack of insight into the visual needs of individuals with visual impairment is a hurdle for the development of more effective assistive technologies.ObjectiveThis study aimed to investigate how needs for visual aids may vary with social activities, by observing the changes in the usage of a smartphone magnifier app when many users take breaks from work.MethodsThe number of launches of the SuperVision Magnifier app was determined retrospectively from 2018 to 2020 from among active users worldwide. The fluctuation in app usage was examined by comparing weekday vs weekend periods, Christmas and new year vs nonholiday seasons, and COVID-19 lockdowns vs the easing of restriction during the pandemic.ResultsOn average, the app was used 262,466 times by 38,237 users each month in 2020 worldwide. There were two major trough points on the timeline of weekly app usage, one aligned with the COVID-19 lockdowns in April 2020 and another aligned with the Christmas and new year week in 2018 and 2019. The app launches declined by 6947 (11% decline; P<.001) during the lockdown and by 5212 (9% decline; P=.001) during the holiday weeks. There was no significant decline during March to May 2019. App usage compensated for seasonal changes was 8.6% less during weekends than during weekdays (P<.001).ConclusionsThe need for vision assistance technology was slightly lower during breaks and lockdowns, probably because the activities at home were different and less visually demanding. Nevertheless, for the entire user population, the needs for visual aids are still substantial.

Application of Google Analytics Model for Evaluating the Visibility of Library Web Portals of the Uva Wellassa University, Sri Lanka

Google Analytics is the most prevalent page tagging technique to evaluate the visibility of web portals. The study was designed with the purpose of applying google analytics model on the library Web Portals (WP) of the Uva Wellassa University (UWU) which includes, Home Page (HP), Online Public Access Catalogue (OPAC) and Institutional Repository (IR). It was observed that the web resources of UWU have been viewed by ~366756 local &amp; global users during the study period. The USA is the predominant country visited the UWU e. Repository with the count of 53,078 (15.82%) followed by Netherlands with 14,044 (4.78%) and France 15,775 (4.70%).

Application of Google Analytics Model for Evaluating the Visibility of Library Web Portals of the Uva Wellassa University, Sri Lanka

Google Analytics is the most prevalent page tagging technique to evaluate the visibility of web portals. The study was designed with the purpose of applying google analytics model on the library Web Portals (WP) of the Uva Wellassa University (UWU) which includes, Home Page (HP), Online Public Access Catalogue (OPAC) and Institutional Repository (IR). It was observed that the web resources of UWU have been viewed by ~366756 local &amp; global users during the study period. The USA is the predominant country visited the UWU e. Repository with the count of 53,078 (15.82%) followed by Netherlands with 14,044 (4.78%) and France 15,775 (4.70%).

Engineers Taking a Stance on Technical Communication: Peer Review of Oral Presentations via the Trans-Atlantic and Pacific Project

Introduction: To present technical content clearly and effectively for global users of English, engineering students need to learn how. About the case: Technical communication classes in Spain and the US engaged in an international telecollaborative project between cross-cultural virtual teams in which students in Spain developed oral presentations that were then peer-reviewed by counterparts in the US. Situating the case: Research on international professional communication and, more specifically, virtual exchange is rapidly growing to explore how instructors can help students gain key competencies such as audience awareness, intercultural sensitivity, and an understanding of English as a lingua franca. Approach/methods: As part of the Trans-Atlantic & Pacific Project network, this project focused on spoken communication. Data were analyzed from feedback forms used by US students to evaluate oral presentations, and on prelearning and postlearning reports completed by students in Spain, as well as from class discussions accompanying the project. Results/discussion: Through reflections on pragmatic strategies that facilitate exchange and collaboration in English as a lingua franca, the engineering students became more fully aware of the importance of rhetorical and linguistic factors that affect meaning-making for engineers internationally. Conclusion: Results suggest that students who participate in transnational virtual exchange projects integrate their desire to acquire knowledge with an awareness of the importance of sharing knowledge through mindful and inclusive communication practices. Technical and engineering communication instructors from different countries can heighten their students' audience awareness, and cultural and language sensitivities through such projects.

Modeling and Analysis of BDS-2 and BDS-3 Combined Precise Time and Frequency Transfer Considering Stochastic Models of Inter-System Bias

BeiDou global navigation satellite system (BDS) began to provide positioning, navigation, and timing (PNT) services to global users officially on 31 July, 2020. BDS constellations consist of regional (BDS-2) and global navigation satellites (BDS-3). Due to the difference of modulations and characteristics for the BDS-2 and BDS-3 default civil service signals (B1I/B3I) and the increase of new signals (B1C/B2a) for BDS-3, a systemically bias exists in the receiver-end when receiving and processing BDS-2 and BDS-3 signals, which leads to the inter-system bias (ISB) between BDS-2 and BDS-3 on the receiver side. To fully utilize BDS, the BDS-2 and BDS-3 combined precise time and frequency transfer are investigated considering the effect of the ISB. Four kinds of ISB stochastic models are presented, which are ignoring ISB (ISBNO), estimating ISB as random constant (ISBCV), random walk process (ISBRW), and white noise process (ISBWN). The results demonstrate that the datum of receiver clock offsets can be unified and the ISB deduced datum confusion can be avoided by estimating the ISB. The ISBCV and ISBRW models are superior to ISBWN. For the BDS-2 and BDS-3 combined precise time and frequency transfer using ISBNO, ISBCV, ISBRW, and ISBWN, the stability of clock differences of old signals can be enhanced by 20.18%, 23.89%, 23.96%, and 11.46% over BDS-2-only, respectively. For new signals, the enhancements are −50.77%, 20.22%, 17.53%, and −3.69%, respectively. Moreover, ISBCV and ISBRW models have the better frequency transfer stability. Consequently, we recommended the optimal ISBCV or suboptimal ISBRW model for BDS-2 and BDS-3 combined precise time and frequency transfer when processing the old as well as the new signals.

Application of Google Analytics Model for Evaluating the Visibility of Library Web Portals of the UVA Wellassa University, Sri Lanka

Google Analytics is the most prevalent page tagging technique to evaluate the visibility of web portals. The study was designed with the purpose of applying google analytics model on the library Web Portals (WP) of the Uva Wellassa University (UWU) which includes, Home Page (HP), Online Public Access Catalogue (OPAC) and Institutional Repository (IR). It was observed that the web resources of UWU have been viewed by 366756 local & global users during the study period. The USA is the predominant country visited the UWU e. Repository with the count of 53,078 (15.82%) followed by Netherlands with 14,044 (4.78%) and France 15,775 (4.70%).

Research on Backup Strategy of BeiDou Global Navigation System Constellation

BeiDou Global Navigation System (BDS-3) will be fully completed by 2020, and provide global users with high-quality services including positioning, navigation and timing, global short messages communication (GSMC), international search and rescue(SAR) etc. Compared with the regional navigation system, the global navigation system serves a wider area and more users, and the consequences are more serious in the event of a service outage. It is necessary to study the backup strategy of the space segment as early as possible in the early stage of system operation. Firstly, the paper analyses the effects of three kinds of satellite in different positions on the system performance, then analyses the probability distribution of multiple satellites failure, and then puts forward the satellite backup strategy. From the perspectives of improving GSMC coverage and increasing the available time of SAR, combined with the remaining life and configuration of the satellites in orbit, the orbit positions of redundancy satellites are suggested. The analysis results show that if one or two satellites are backed up in three MEO orbital planes, the robustness of the system will be improved effectively, and the availability of the system will be guaranteed even if any satellite fails. Furthermore, if four satellites equipped with SAR and GSMC load are backed up in proper phase on the first and third orbit planes, the availability of GSMC service will reach 100% in the global scope, and the availability of SAR service will be significantly improved.

Analysis of the Beidou navigation satellite system: Interoperability and performance

Based on the new trends and requirements introduced by the development of the international navigation satellite systems from the single global positioning system (GPS) era to the multiple global navigation satellite system (GNSS) era, the Beidou-3 navigation satellite system (BDS-3) has been designed to ensure compatibility and interoperability with other GNSS systems based on four features, i.e., constellation, signal, time, and coordinate. In terms of constellation design, the BDS-3 constellation orbit altitude and inclination design consider the constellation complementary requirements with the GPS, GLONASS, and Galileo systems. Thus, the PDOP of GNSS improves by 37.9% on average. BDS has acquired interoperability with respect to the signal structure; therefore, it is in agreement with other systems using a similar frequency and spectrum. Thus, users can simultaneously use the navigation services of each major system without changing the hardware design. In terms of time and coordinate, BDS has realized a reference system that is considerably consistent with the systems used on an international scale, resulting in a time difference offset of 50 ns with international UTC and GLNT, which is consistent with the international ITRF 2014 coordinate parameter accuracy. Thus, BDS-3 has achieved interoperability with other GNSSs based on the four aforementioned aspects and can provide better service to global users in combination with other GNSSs.

Satellite availability and positioning performance of uncombined precise point positioning using BeiDou-2 and BeiDou-3 multi-frequency signals

To realize the smooth transition from regional BeiDou Navigation Satellite System (BDS-2) to the global one (BDS-3), the integration of BDS-2 and BDS-3 is important for providing continuous, stable and reliable positioning, navigation and timing (PNT) services for global users. This work used 154 globally distributed multi-GNSS (Global Navigation Satellite System) experiment stations spanning 30 days to analyze the satellite availability and positioning performance of uncombined precise point positioning (UC-PPP) under current BDS-2 and BDS-3 constellations. We focused on three issues: the influence of BDS-3 receiver tracking abilities, the positioning performance among different areas, and the benefit of multi-frequency observations. The results show that the elliptical zone caused by poor BDS-2 satellite visibility is disappeared when the evenly distributed BDS-3 medium earth orbit satellites are introduced. When BDS-3 are integrated with BDS-2, the area with the Position Dilution of Precision (PDOP) less than 2 can be expanded to 75° S-75° N and 30° E-150° W. The positioning performance of BDS-3 and BDS-2/BDS-3 UC-PPP are seriously affected by the receiver tracking abilities of BDS-3 signals. When the maximum pseudo-random noise sequences (PRNs) of BDS-3 satellites tracked by stations are within 30 or 37, the positioning accuracy of static UC-PPP can be improved by 22.94% or 8.27% due to the integration of BDS-2 and BDS-3. Besides, the most improvement of BDS-2 and BDS-3 integration is achieved in Asia-Pacific regions, especially for the kinematic UC-PPP or the poor receiver tracking abilities of BDS-3. Similar to the multi-frequency BDS-2 UC-PPP, the benefit of multi-frequency signals for BDS-3 or BDS-2/BDS-3 UC-PPP is also non-vital. The three-dimensional positioning accuracy of BDS-2/BDS-3 multi-frequency UC-PPP in static mode and kinematic mode are 2.24 cm and 5.39 cm, while the corresponding convergence time are 49.62 min and 73.80 min, respectively. Compared with BDS-2, both the positioning accuracy and the convergence time of BDS-2/BDS-3 joint UC-PPP are improved by approximately over 50%, which indicates that BDS-3 has a great potential to provide high-quality PNT services as other global navigation satellite systems.

Initial assessment of single- and dual-frequency BDS-3 RTK positioning

The BeiDou navigation satellite system with global coverage (BDS-3) has been fully operational since July 2020 and provides comprehensive services to global users. BDS-3 transmits several new navigational signals based on the signals inherited from the BeiDou navigation satellite (regional) system (BDS-2). Previous studies focused on the positioning performance of BDS-2 plus BDS-3 and that of combining BDS-3 and other Global Navigation Satellite Systems (GNSSs), but there was no in-depth discussion on the positioning performance of the BDS-3-only. In this contribution, the BDS-3-only Real-Time Kinematic (RTK) positioning is analysed using the data collected in zero and short baselines in Wuhan, China. The RTK model based on Single-Differenced is first presented, and the BDS-3-only RTK positioning in cases of single and dual-frequencies is evaluated with the model in terms of the empirical integer ambiguity resolution success rates and positioning accuracy. Our numerical tests suggest two major findings. First, the positioning performance for the B1I and B3I retained from BDS-2 and the new frequency B1C is comparable, while that for the new frequency B2a is poorer. Second, the positioning performance of the new frequency combination of the B1C + B2a is not as good as that of the B1C only, owing to the unrealistic stochastic model used.

An energy management maturity model for China: Linking ISO 50001:2018 and domestic practices

Well-structured Energy Management Maturity Models (EMMMs) are advanced and easy-to-use energy management (EM) approaches for energy management systems (EnMSs), providing both qualitative metrics and improvement guidelines. And the metrics serve the most valuable role. To furnish the users in different contexts (regional or industrial) with optimal applicability, an EMMM should deliver the most specific, precise, and valid metrics. It requires the latest explorations of this domain to evolve from the existing prototypes and keep improving the theoretical hypotheses about EM maturation, particularly for emerging economies like China. Accordingly, this study attempts to propose a highly practice-based Energy Management Maturity Model for China (EMMM-China), intending to make twofold contributions to this domain. For the methodological perspective, this study has demonstrated a set of highly referable strategies to felicitously formulate a model’s metrics. A solid knowledge base for deducing hypotheses, encompassing both EM imperfections and good practices, was crucially constructed by taking in empirical experience from scientific literature and over 70 domestic cases. On this basis, five maturity levels and four maturation phases were justifiably defined. To validate the reliability of the model, three industrial cases were repeatedly assessed by EMMM-China in a longitudinal study design. And for the outcome perspective, EMMM-China serves as a new ISO 50001-based model for global users. The High Level Structure (HLS) of ISO 50001:2018 and numerous widely recognized success factors for EM were both adopted. With extended knowledge that goes beyond EnMS standards, EMMM-China enables long-term applicability to even certified organizations. The proposed model is believed to work on China and other emerging economies as a referable meta-approach. • A comprehensive strategy to construct a solid knowledge base was demonstrated. • Energy management practices in China were characterized by massive domestic cases. • A maturity model based on ISO 50001:2018 was proposed for China and other emerging economies. • Five maturity levels were justifiably defined, along with four maturation phases. • The model was validated through a longitudinal study of three industrial cases.

Locally-Centralized Certificate Validation and its Application in Desktop Virtualization Systems

To validate a certificate, a user needs to install the certificate of the root certification authority (CA) and download the certificate revocation information (CRI). Although operating systems and browsers manage the certificate trust list (CTL) of publicly-trusted root CAs for global users, locally-trusted root CAs still play an important role and it is difficult for a user to manage its CTL properly by itself. Meanwhile, the CRI access is inefficient, sometimes even unavailable, and causes privacy leakage. We revisit these problems by analyzing the TLS sessions within an organization. To the best of our knowledge, we are the first to analyze CTL management and CRI access on the scale of medium-sized organizations. Based on the analysis, a locally-centralized design is proposed to manage the CTLs of all users by IT administrators and access the CRI services for all users, within an organization. We apply this design to desktop virtualization systems to demonstrate its applicability, and build vCertGuard with oVirt and KVM-QEMU. In vCertGuard, the CTLs of all virtual machines (VMs) are managed in the VM monitors (VMMs). In the CTL, the self-signed certificates of publicly-trusted root CAs are properly configured, while each locally-trusted certificate chain is specified one by one. vCertGuard accesses the CRI services for all VMs, and the downloaded CRI is cached and shared among VMs. Because most TLS servers are visited by multiple users of an organization, it reduces the cost of CRI access. Experimental results of the prototype system show that vCertGuard maintains the CTLs with a negligible overhead, and significantly improves the performance of CRI access.

Analysis on the time transfer performance of BDS-3 signals

The BeiDou global navigation satellite system (BDS-3) was formally commissioned to provide positioning, velocity, and timing services to global users on 31 July 2020. We analyzed its pseudorange measurement noise, the precision of conventional common view (CV) and all-in-view (AV) time comparison, and the instability of the precise point positioning (PPP) time transfer to assess the time transfer performance of BDS-3. We found that the elevation-dependent biases found in BDS-2 code measurements are mitigated in BDS-3. The time transfer performance of the BDS-3 satellites is over 50% higher than that of the BDS-2 satellites. In terms of the CV time comparison, the standard deviations of the zero-baseline common clock time comparison of the new BDS-3 signal combination of B1C and B2a reach 0.36 ns, which are the same levels for Galileo E1 and E5a and the global positioning system (GPS) L1 and L2. In the long baseline AV comparison links over 7000 km, the standard deviation of the time comparison of the B1C and B2a combination also reaches 0.8 ns, and the improved gain is 55% relative to that of the BDS-2 B1I and B2I. We also tested the PPP time transfer performance with BDS-2 and BDS-3 satellites and found that the time transfer performance of BDS B1I and B3I is comparable to that of GPS L1 and L2.

Strengthening Collaborative Action for Community Health and Development

Collaborative action and engagement are essential for improving community health and development. Effective community action requires a prepared workforce working together in common purpose. Yet, supports for collaborative action are limited given the need. This article outlines a framework for collaborative action; highlighting core processes associated with assessment, mobilization, planning, intervention, and evaluation and sustainability. We describe tools for building capacity for collaborative action, including our experience in developing the Community Tool Box with over 5.6 million global users. We illustrate core processes for community engagement with examples of collaborative efforts that promote community health.