8 research outputs found
Robust Localization of Aerial Vehicles via Active Control of Identical Ground Vehicles
This paper addresses the problem of active collaborative localization in
heterogeneous robot teams with unknown data association. It involves
positioning a small number of identical unmanned ground vehicles (UGVs) at
desired positions so that an unmanned aerial vehicle (UAV) can, through
unlabelled measurements of UGVs, uniquely determine its global pose. We model
the problem as a sequential two player game, in which the first player
positions the UGVs and the second identifies the two distinct hypothetical
poses of the UAV at which the sets of measurements to the UGVs differ by as
little as possible. We solve the underlying problem from the vantage point of
the first player for a subclass of measurement models using a mixture of local
optimization and exhaustive search procedures. Real-world experiments with a
team of UAV and UGVs show that our method can achieve centimeter-level global
localization accuracy. We also show that our method consistently outperforms
random positioning of UGVs by a large margin, with as much as a 90% reduction
in position and angular estimation error. Our method can tolerate a significant
amount of random as well as non-stochastic measurement noise. This indicates
its potential for reliable state estimation on board size, weight, and power
(SWaP) constrained UAVs. This work enables robust localization in
perceptually-challenged GPS-denied environments, thus paving the road for
large-scale multi-robot navigation and mapping.Comment: To appear in IROS 202
Active Metric-Semantic Mapping by Multiple Aerial Robots
Traditional approaches for active mapping focus on building geometric maps.
For most real-world applications, however, actionable information is related to
semantically meaningful objects in the environment. We propose an approach to
the active metric-semantic mapping problem that enables multiple heterogeneous
robots to collaboratively build a map of the environment. The robots actively
explore to minimize the uncertainties in both semantic (object classification)
and geometric (object modeling) information. We represent the environment using
informative but sparse object models, each consisting of a basic shape and a
semantic class label, and characterize uncertainties empirically using a large
amount of real-world data. Given a prior map, we use this model to select
actions for each robot to minimize uncertainties. The performance of our
algorithm is demonstrated through multi-robot experiments in diverse real-world
environments. The proposed framework is applicable to a wide range of
real-world problems, such as precision agriculture, infrastructure inspection,
and asset mapping in factories. A demo video can be found at
https://youtu.be/S86SgXi54oU.Comment: ICRA 2023 (2023 International Conference on Robotics and Automation
Mortality from gastrointestinal congenital anomalies at 264 hospitals in 74 low-income, middle-income, and high-income countries: a multicentre, international, prospective cohort study
Summary
Background Congenital anomalies are the fifth leading cause of mortality in children younger than 5 years globally.
Many gastrointestinal congenital anomalies are fatal without timely access to neonatal surgical care, but few studies
have been done on these conditions in low-income and middle-income countries (LMICs). We compared outcomes of
the seven most common gastrointestinal congenital anomalies in low-income, middle-income, and high-income
countries globally, and identified factors associated with mortality.
Methods We did a multicentre, international prospective cohort study of patients younger than 16 years, presenting to
hospital for the first time with oesophageal atresia, congenital diaphragmatic hernia, intestinal atresia, gastroschisis,
exomphalos, anorectal malformation, and Hirschsprung’s disease. Recruitment was of consecutive patients for a
minimum of 1 month between October, 2018, and April, 2019. We collected data on patient demographics, clinical
status, interventions, and outcomes using the REDCap platform. Patients were followed up for 30 days after primary
intervention, or 30 days after admission if they did not receive an intervention. The primary outcome was all-cause,
in-hospital mortality for all conditions combined and each condition individually, stratified by country income status.
We did a complete case analysis.
Findings We included 3849 patients with 3975 study conditions (560 with oesophageal atresia, 448 with congenital
diaphragmatic hernia, 681 with intestinal atresia, 453 with gastroschisis, 325 with exomphalos, 991 with anorectal
malformation, and 517 with Hirschsprung’s disease) from 264 hospitals (89 in high-income countries, 166 in middleincome
countries, and nine in low-income countries) in 74 countries. Of the 3849 patients, 2231 (58·0%) were male.
Median gestational age at birth was 38 weeks (IQR 36–39) and median bodyweight at presentation was 2·8 kg (2·3–3·3).
Mortality among all patients was 37 (39·8%) of 93 in low-income countries, 583 (20·4%) of 2860 in middle-income
countries, and 50 (5·6%) of 896 in high-income countries (p<0·0001 between all country income groups).
Gastroschisis had the greatest difference in mortality between country income strata (nine [90·0%] of ten in lowincome
countries, 97 [31·9%] of 304 in middle-income countries, and two [1·4%] of 139 in high-income countries;
p≤0·0001 between all country income groups). Factors significantly associated with higher mortality for all patients
combined included country income status (low-income vs high-income countries, risk ratio 2·78 [95% CI 1·88–4·11],
p<0·0001; middle-income vs high-income countries, 2·11 [1·59–2·79], p<0·0001), sepsis at presentation (1·20
[1·04–1·40], p=0·016), higher American Society of Anesthesiologists (ASA) score at primary intervention
(ASA 4–5 vs ASA 1–2, 1·82 [1·40–2·35], p<0·0001; ASA 3 vs ASA 1–2, 1·58, [1·30–1·92], p<0·0001]), surgical safety
checklist not used (1·39 [1·02–1·90], p=0·035), and ventilation or parenteral nutrition unavailable when needed
(ventilation 1·96, [1·41–2·71], p=0·0001; parenteral nutrition 1·35, [1·05–1·74], p=0·018). Administration of
parenteral nutrition (0·61, [0·47–0·79], p=0·0002) and use of a peripherally inserted central catheter (0·65
[0·50–0·86], p=0·0024) or percutaneous central line (0·69 [0·48–1·00], p=0·049) were associated with lower mortality.
Interpretation Unacceptable differences in mortality exist for gastrointestinal congenital anomalies between lowincome,
middle-income, and high-income countries. Improving access to quality neonatal surgical care in LMICs will
be vital to achieve Sustainable Development Goal 3.2 of ending preventable deaths in neonates and children younger
than 5 years by 2030
Trap Assisted Avalanche Instability and Safe Operating Area Concerns in AlGaN/GaN HEMTs
This work reports the very first systematic study on the physics of avalanche instability and SOA concerns in AlGaN/GaN HEMT using sub-mu s pulse characterization, post stress degradation analysis, well calibrated TCAD simulations and failure analysis by SEM and TEM. Impact of electrical, as well as thermal effects on SOA boundary and avalanche instability are investigated. Trap assisted cumulative nature of degradation is studied in detail, which was discovered to be the root cause for avalanche instability in AlGaN/GaN HEMTs. Post failure SEM/TEM analysis reveal distinct failure modes in presence and absence of carrier trapping
Abstracts of National Conference on Research and Developments in Material Processing, Modelling and Characterization 2020
This book presents the abstracts of the papers presented to the Online National Conference on Research and Developments in Material Processing, Modelling and Characterization 2020 (RDMPMC-2020) held on 26th and 27th August 2020 organized by the Department of Metallurgical and Materials Science in Association with the Department of Production and Industrial Engineering, National Institute of Technology Jamshedpur, Jharkhand, India.
Conference Title: National Conference on Research and Developments in Material Processing, Modelling and Characterization 2020Conference Acronym: RDMPMC-2020Conference Date: 26–27 August 2020Conference Location: Online (Virtual Mode)Conference Organizer: Department of Metallurgical and Materials Engineering, National Institute of Technology JamshedpurCo-organizer: Department of Production and Industrial Engineering, National Institute of Technology Jamshedpur, Jharkhand, IndiaConference Sponsor: TEQIP-