Autonomous Navigation of Distributed Spacecraft using Graph-based SLAM for Proximity Operations in Small Celestial Bodies

Establishment of a sustainable human presence beyond the cislunar space is a major milestone for mankind. Small celestial bodies (SCBs) like asteroids are known to contain valuable natural resources necessary for the development of space assets essential to the accomplishment of this goal. Consequently, future robotic spacecraft missions to SCBs are envisioned with the objective of commercial in-situ resource utilization (ISRU). In mission design, there is also an increasing interest in the utilization of the distributed spacecraft, to benefit from specialization and redundancy. The ability of distributed spacecraft to navigate autonomously in the proximity of a SCB is indispensable for the successful realization of ISRU mission objectives. Quasi-autonomous methods currently used for proximity navigation require extensive ground support for mapping and model development, which can be an impediment for large scale multi-spacecraft ISRU missions in the future. It is prudent to leverage the advances in terrestrial robotic navigation to investigate the development of novel methods for autonomous navigation of spacecraft. The primary objective of the work presented in this thesis is to evaluate the feasibility and investigate the development of methods based on graph-based simultaneous localization and mapping (SLAM), a popular algorithm used in terrestrial autonomous navigation, for the autonomous navigation of distributed spacecraft in the proximity of SCBs. To this end, recent research in graph-based SLAM is extensively studied to identify strategies used to enable multi-agent navigation. The spacecraft navigation requirement is formulated as a graph-based SLAM problem using metric GraphSLAM or topometric graph-based SLAM. Techniques developed based on the identified strategies namely, map merging, inter-spacecraft measurements and relative localization are then applied to this formulation to enable distributed spacecraft navigation. In each case, navigation is formulated in terms of its application to a proximity operation scenario that best suits the multi-agent navigation technique. Several challenges related to the application of graph-based SLAM for spacecraft navigation, such as computational cost and illumination variation are also identified and addressed in the development of these methods. Experiments are performed using simulated models of asteroids and spacecraft dynamics, comparing the estimated states of the spacecraft and landmarks to the assumed true states. The results from the experiments indicate a consistent and robust state determination process, suggesting the suitability of the application of multi-agent navigation techniques to graph-based SLAM for enabling the autonomous navigation of distributed spacecraft near SCBs

Molecular characterisation of membrane glycoprotein and 5b protein of nephropathogenic infectious bronchitis virus

Background: Infectious bronchitis virus (IBV) affects the upper respiratory tract and the reproductive tract, and some strainscan cause nephritis. Large number of serotypes and genotypes of the virus have been identified and for the most part do notcross-protect. Identifying the genotype or serotype of IBV field strains is empirical for selecting an appropriate candidate toserve as vaccine strain for prevention of infectious bronchitis (IB) disease in chickens. The variant strains of IBV could becirculating among chickens in India and recently nephropathogenic IB was reported. Hence, the present work was aimed tocarry out molecular characterization of nephropathogenic IBV isolates obtained from two different geographical locations ofsouth India, involving relatively conserved regions.Materials and Methods: MIBVPCR and NIBVPCR primers were used to amplify partial M and N gene after synthesizingcDNA. Isolates Ind/KA/07/1 and Ind/TN/07/2 were subjected to direct sequencing as these two isolates are two differentgeographical regions and scored better in induction of lesions during pathotyping.Results: Amino acids of membrane glycoprotein varied on five occasions for the isolate Ind/KA/07/1 when aligned with thatof M 41 strain and isolate Ind/TN/07/2. Eight amino acids of both isolates in 5b protein were different from that of M41 strain.Few point mutations, short deletions and insertions were noticed in the amplified genome, based on the membrane proteinnucleotide sequence comparison.Conclusion: Prevalence of IBV strains with few modifications in conserved regions indicated that there was presence ofvariant IBVin south India

Application of ARIMAX model for forecasting paddy production in Trincomalee district in Sri Lanka

In the post-war climes, the government’s mandates focus on reviving one of the paddy production region Trincomalee district in SriLanka to meet the growing demands of the nation. Such a rehabilitation program requires the understanding of how the paddy producing industry has fared along the historical time-lines. This understanding is essential for developing the necessary development plans for the Rice sector. When an ARIMA model includes other time series as input variables, the model is referred to as an ARIMAX model. Pankratz (1991). In this paper, ARIMAX model has been applied to forecast annual paddy production with includes rainfall time series as input variable for both seasons in this district. The validity of the model is verified with various model selection criteria such as Adj R2, minimum of AIC and SBC lowest MAPE value

An econometric study of labor market in Sri Lanka with special reference to demographic characteristics of labor

The wage in labor market has drastically changed during the past centuryand gone through different stages and changed with socioeconomic determinants. Among the concepts of labor, demand and supply of labor are very important in practical sense. The determination of wages in a free market simply depends on the socioeconomic characteristics of the labor force. Therefore, an attempt is made to explore the relationships between the wage rates and demographic characteristics of labor force using econometric methods. The required data are obtained from the records of Labor Force and Socioeconomic Survey conducted by the Department of Census and Statistics. An econometric model for wage rates using the demographic characteristics as independent variables is fitted and verified. The study reveals that age, gender, civil status, ethnicity etc. have significant influences in determining the wages. Hence, it is emphasized that the demographic characteristics should be taken into consideration whendetermining the wages of aparticular labor force inherited in the respective areas of the country. This study specifically reports that the general effect of hourly wage rate in Sri Lanka is 2.566 when ignoring the socio-demographic characteristics of labor force and the average hourly wage rate difference by gender is 0.294 and difference by marital status is 0.162. Further, the average hourly wage rate differences in the three ethnic groups Sinhalese, Sri Lankan Tamil, and Indian Tamil were individually found to be 0.034, 0.008, and 0.352 discriminated from rest of the ethnic groups. Similar hourly wage rate differences for employees of the Government sector and Semigovernment sector were found to be 0.28.and 0.19. The effects or differences in hourly wage rates due to educational levels and literacy rates of the employees in Sri Lankan labor market are also reported in this study

Orthotopic Liver Transplantation in a Case of Novel YAP1-TFE3 Hepatic Epithelioid Hemangioendothelioma [HEHE]; Case Report and Review of Literature

Epithelioid hemangioendothelioma is an extremely rare vascular neoplasm arising in soft-tissues and different visceral organs, with liver being the most commonly involved viscera. Hepatic epithelioid hemangioendothelioma (HEHE) is a malignant tumour with an indolent behaviour and unpredictable clinical course. It has a better prognosis among the malignant tumours of the liver, in spite of being a diffuse multifocal liver disease or metastatic at the time of presentation. HEHE is usually found to be noted in the fifth decade with slight female preponderance. No single treatment strategy has yet been established owing to its variable clinical course, ranging from an indolent tumour with prolonged survival to an aggressive, metastatic disease with a fatal outcome. Here, we present a case of a novel HEHE in a 25-year-old female who was treated successfully with orthotopic living donor liver transplantation and discuss the presentation, histopathology and management of this rare, fatal yet treatable malignant tumour

Genotypic and Pathotypic Characterization of Newcastle Disease Viruses from India

Newcastle disease virus (NDV) is an avian paramyxovirus that causes significant economic losses to the poultry industry in most parts of the world. The susceptibility of a wide variety of avian species coupled with synanthropic bird reservoirs has contributed to the vast genomic diversity of this virus as well as diagnostic failures. Since the first panzootic in 1926, Newcastle disease (ND) became enzootic in India with recurrent outbreaks in multiple avian species. The genetic characteristics of circulating strains in India, however, are largely unknown. To understand the nature of NDV genotypes in India, we characterized two representative strains isolated 13 years apart from a chicken and a pigeon by complete genome sequence analysis and pathotyping. The viruses were characterized as velogenic by pathogenicity indices devised to distinguish these strains. The genome length was 15,186 nucleotides (nt) and consisted of six non-overlapping genes, with conserved and complementary 3′ leader and 5′ trailer regions, conserved gene starts, gene stops, and intergenic sequences similar to those in avian paramyxovirus 1 (APMV-1) strains. Matrix gene sequence analysis grouped the pigeon isolate with APMV-1 strains. Phylogeny based on the fusion (F), and hemagglutinin (HN) genes and complete genome sequence grouped these viruses into genotype IV. Genotype IV strains are considered to have “died out” after the first panzootic (1926–1960) of ND. But, our results suggest that there is persistence of genotype IV strains in India

A critical analysis of open protocol for subsea production controls system communication.

Production control system communication protocols used in subsea fields are primarily proprietary to the subsea vendor. Due to the proprietary nature of this communication system, the operators encounter many challenges including obsolescence management, knowledge management and conformity assessment. This paper presents an investigation of the option of using open standard protocols for subsea production control communication system. The features, functionality and standardization of existing communication protocols used in subsea control system are analyzed and compared with open standard protocols such as DNP3 (Distributed Network Protocol) and IEC60870-5-101 and their variants used with Transmission Control Protocol/Internet Protocol (TCP/IP). The features of open standard protocols were also analyzed along with the possibility of its use in subsea production control system communication. The analysis showed that the open standard protocol DNP3 and DNP3 over TCP/IP could provide significant advantages over proprietary protocols as the specifications of DNP3 are publicly available and controlled by non-profit user group. DNP3 supports unsolicited response messages, time stamping, peer-to-peer communication and its implementation can be verified by external bodies. Furthermore, DNP3 allows the operator to integrate multiple vendors' products on a single subsea network and allows the integration of slower network with faster network without losing the data throughput

Close genetic linkage between human and companion animal extraintestinal pathogenic Escherichia coli ST127

Escherichia coli ST127, a recently emerged global pathogen noted for high virulence gene carriage, is a leading cause of urinary tract and blood stream infections. ST127 is frequently isolated from humans and companion animals; however, it is unclear if they are distinct or related populations of ST127. We performed a phylogenomic analysis of 299 E. coli ST127 of diverse epidemiological origin to characterize their population structure, genetic determinants of virulence, antimicrobial resistance, and repertoire of mobile genetic elements with a focus on plasmids. The core gene phylogeny was divided into 13 clusters, the largest of which (BAP4) contained the majority of human and companion animal origin isolates. This dominant cluster displayed genetic differences to the remainder of the phylogeny, most notably alternative gene alleles encoding important virulence factors including lipid A, flagella, and K capsule. Furthermore, numerous close genetic linkages (<30 SNPs) between human and companion animal isolates were observed within the cluster. Carriage of antimicrobial resistance genes in the collection was limited, but virulence gene carriage was extensive. We found evidence of pUTI89-like virulence plasmid carriage in over a third of isolates, localised to four of the major phylogenetic clusters. Our study supports global scale repetitive transfer of E. coli ST127 lineages between humans and companion animals, particularly within the dominant BAP4 cluster

Protocolised non-invasive compared with invasive weaning from mechanical ventilation for adults in intensive care : the Breathe RCT

Background: Invasive mechanical ventilation (IMV) is a life-saving intervention. Following resolution of the condition that necessitated IMV, a spontaneous breathing trial (SBT) is used to determine patient readiness for IMV discontinuation. In patients who fail one or more SBTs, there is uncertainty as to the optimum management strategy. Objective: To evaluate the clinical effectiveness and cost-effectiveness of using non-invasive ventilation (NIV) as an intermediate step in the protocolised weaning of patients from IMV. Design: Pragmatic, open-label, parallel-group randomised controlled trial, with cost-effectiveness analysis. Setting: A total of 51 critical care units across the UK. Participants: Adult intensive care patients who had received IMV for at least 48 hours, who were categorised as ready to wean from ventilation, and who failed a SBT. Interventions: Control group (invasive weaning): patients continued to receive IMV with daily SBTs. A weaning protocol was used to wean pressure support based on the patient’s condition. Intervention group (non-invasive weaning): patients were extubated to NIV. A weaning protocol was used to wean inspiratory positive airway pressure, based on the patient’s condition. Main outcome measures: The primary outcome measure was time to liberation from ventilation. Secondary outcome measures included mortality, duration of IMV, proportion of patients receiving antibiotics for a presumed respiratory infection and health-related quality of life. Results: A total of 364 patients (invasive weaning, n = 182; non-invasive weaning, n = 182) were randomised. Groups were well matched at baseline. There was no difference between the invasive weaning and non-invasive weaning groups in median time to liberation from ventilation {invasive weaning 108 hours [interquartile range (IQR) 57–351 hours] vs. non-invasive weaning 104.3 hours [IQR 34.5–297 hours]; hazard ratio 1.1, 95% confidence interval [CI] 0.89 to 1.39; p = 0.352}. There was also no difference in mortality between groups at any time point. Patients in the non-invasive weaning group had fewer IMV days [invasive weaning 4 days (IQR 2–11 days) vs. non-invasive weaning 1 day (IQR 0–7 days); adjusted mean difference –3.1 days, 95% CI –5.75 to –0.51 days]. In addition, fewer non-invasive weaning patients required antibiotics for a respiratory infection [odds ratio (OR) 0.60, 95% CI 0.41 to 1.00; p = 0.048]. A higher proportion of non-invasive weaning patients required reintubation than those in the invasive weaning group (OR 2.00, 95% CI 1.27 to 3.24). The within-trial economic evaluation showed that NIV was associated with a lower net cost and a higher net effect, and was dominant in health economic terms. The probability that NIV was cost-effective was estimated at 0.58 at a cost-effectiveness threshold of £20,000 per quality-adjusted life-year. Conclusions: A protocolised non-invasive weaning strategy did not reduce time to liberation from ventilation. However, patients who underwent non-invasive weaning had fewer days requiring IMV and required fewer antibiotics for respiratory infections. Future work: In patients who fail a SBT, which factors predict an adverse outcome (reintubation, tracheostomy, death) if extubated and weaned using NIV? Trial registration: Current Controlled Trials ISRCTN15635197. Funding: This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 23, No. 48. See the NIHR Journals Library website for further project information