97 research outputs found
Visual-UWB Navigation System for Unknown Environments
Navigation applications relying on the Global Navigation Satellite System
(GNSS) are limited in indoor environments and GNSS-denied outdoor terrains such
as dense urban or forests. In this paper, we present a novel accurate, robust
and low-cost GNSS-independent navigation system, which is composed of a
monocular camera and Ultra-wideband (UWB) transceivers. Visual techniques have
gained excellent results when computing the incremental motion of the sensor,
and UWB methods have proved to provide promising localization accuracy due to
the high time resolution of the UWB ranging signals. However, the monocular
visual techniques with scale ambiguity are not suitable for applications
requiring metric results, and UWB methods assume that the positions of the UWB
transceiver anchor are pre-calibrated and known, thus precluding their
application in unknown and challenging environments. To this end, we advocate
leveraging the monocular camera and UWB to create a map of visual features and
UWB anchors. We propose a visual-UWB Simultaneous Localization and Mapping
(SLAM) algorithm which tightly combines visual and UWB measurements to form a
joint non-linear optimization problem on Lie-Manifold. The 6 Degrees of Freedom
(DoF) state of the vehicles and the map are estimated by minimizing the UWB
ranging errors and landmark reprojection errors. Our navigation system starts
with an exploratory task which performs the real-time visual-UWB SLAM to obtain
the global map, then the navigation task by reusing this global map. The tasks
can be performed by different vehicles in terms of equipped sensors and payload
capability in a heterogeneous team. We validate our system on the public
datasets, achieving typical centimeter accuracy and 0.1% scale error.Comment: Proceedings of the 31st International Technical Meeting of the
Satellite Division of The Institute of Navigation (ION GNSS+ 2018
TCP-Mobile Edge: Accelerating Delivery in Mobile Networks
Abstract-Owing to the imminent fixed mobile convergence, Internet applications are frequently accessed through mobile nodes. However, service delivery latency is too high to satisfy user expectations. In this paper, we design a new TCP algorithm, TCP-ME (Mobile Edge), to accelerate the service delivery in mobile networks. Considering the QoS (Quality of Service) mechanisms of mobile networks, TCP-ME is designed to differentiate the packet loss caused by wireless errors, traffic conditioning of mobile core networks, and Internet congestion, as well as to react to the packet loss accordingly. To detect wireless errors, we mark the ACK (Acknowledge) packets in the uplink direction at the base station, and the marking threshold is a function of the instantaneous downlink queue length and the number of consecutive HARQ retransmissions. We modify the ECN mechanism with deterministic marking to detect Internet congestion. The packet loss caused by traffic conditioners of mobile networks is detected by whether the incoming DUPACK is marked or not. TCP-ME adapts the inter-packet interval when the packet loss is caused by wireless errors or the admission control mechanism. If the packet loss is due to Internet congestion, TCP-ME applies the TCP-New Reno's congestion window adaptation algorithm. Simulation results show that TCP-ME can speed up web service response time in mobile networks by about 80%
Surface states in bulk single crystal of topological semimetal Co3Sn2S2 toward water oxidation
The band inversion in topological phase matters bring exotic physical properties such as the topologically protected surface states (TSS). They strongly influence the surface electronic structures of the materials and could serve as a good platform to gain insight into the surface reactions. Here we synthesized high-quality bulk single crystals of Co3Sn2S2 that naturally hosts the band structure of a topological semimetal. This guarantees the existence of robust TSS from the Co atoms. Co3Sn2S2 crystals expose their Kagome lattice that constructed by Co atoms and have high electrical conductivity. They serves as catalytic centers for oxygen evolution process (OER), making bonding and electron transfer more efficient due to the partially filled orbital. The bulk single crystal exhibits outstanding OER catalytic performance, although the surface area is much smaller than that of Co-based nanostructured catalysts. Our findings emphasize the importance of tailoring TSS for the rational design of high-activity electrocatalysts
16S rRNA gene sequencing reveals the correlation between the gut microbiota and the susceptibility to pathological scars
The gut microbiome profile in patients with pathological scars remains rarely known, especially those patients who are susceptible to pathological scars. Previous studies demonstrated that gut microbial dysbiosis can promote the development of a series of diseases via the interaction between gut microbiota and host. The current study aimed to explore the gut microbiota of patients who are prone to suffer from pathological scars. 35 patients with pathological scars (PS group) and 40 patients with normal scars (NS group) were recruited for collection of fecal samples to sequence the 16S ribosomal RNA (16S rRNA) V3-V4 region of gut microbiota. Alpha diversity of gut microbiota showed a significant difference between NS group and PS group, and beta diversity indicated that the composition of gut microbiota in NS and PS participants was different, which implied that dysbiosis exhibits in patients who are susceptible to pathological scars. Based on phylum, genus, species levels, we demonstrated that the changing in some gut microbiota (Firmicutes; Bacteroides; Escherichia coli, etc.) may contribute to the occurrence or development of pathological scars. Moreover, the interaction network of gut microbiota in NS and PS group clearly revealed the different interaction model of each group. Our study has preliminary confirmed that dysbiosis exhibits in patients who are susceptible to pathological scars, and provide a new insight regarding the role of the gut microbiome in PS development and progression
Molecular targets associated with ulcerative colitis and the benefits of atractylenolides-based therapy
Ulcerative colitis (UC) is a chronic inflammatory disease of the intestines that can significantly impact quality of life and lead to various complications. Currently, 5-aminosalicylic acid derivatives, corticosteroids, immunosuppressants, and biologics are the major treatment strategies for UC, but their limitations have raised concerns. Atractylenolides (ATs), sesquiterpene metabolites found in Atractylodes macrocephala Koidz., have shown promising effects in treating UC by exerting immune barrier modulation, alleviating oxidative stress, gut microbiota regulation, improving mitochondrial dysfunction and repairing the intestinal barrier. Furthermore, ATs have been shown to possess remarkable anti-fibrosis, anti-thrombus, anti-angiogenesis and anti-cancer. These findings suggest that ATs hold important potential in treating UC and its complications. Therefore, this review systematically summarizes the efficacy and potential mechanisms of ATs in treating UC and its complications, providing the latest insights for further research and clinical applications
A hydrogen-dependent geochemical analogue of primordial carbon and energy metabolism
Hydrogen gas, H2, is generated by alkaline hydrothermal vents through an ancient geochemical process called serpentinization in which water reacts with iron containing minerals deep within the Earth's crust. H2 is the electron donor for the most ancient and the only energy releasing route of biological CO2 fixation, the acetyl-CoA pathway. At the origin of metabolism, CO2 fixation by hydrothermal H2 within serpentinizing systems could have preceded and patterned biotic pathways. Here we show that three hydrothermal minerals—greigite (Fe3S4), magnetite (Fe3O4) and awaruite (Ni3Fe)—catalyse the fixation of CO2 with H2 at 100°C under alkaline aqueous conditions. The product spectrum includes formate (up to 200 mM), acetate (up to 100 µM), pyruvate (up to 10 µM), methanol (up to 100 µM), and methane. The results shed light on both the geochemical origin of microbial metabolism and on the nature of abiotic formate and methane synthesis in modern hydrothermal vents
Environmental performance assessment of european countries
The European Union(EU) has been promoting an integrated approach to climate protection and energy policy, through a set of key objectives for 2020, 2030 and 2050, linking Europe’s green agenda with its need for energy security and competitiveness.This paper aims to evaluate the environmental efficiency of European Countries from 2010 to 2015 towards the set targets, through a Data Envelopment Analysis (DEA) model.The DEA model assesses the ability of each country in minimizing current resources while maximizing the gross domestic product and minimizing undesirable outputs,such as GHG emissions.The DEA model is based on directional distance Function, imposing weak disposability for the undesirable output. Results obtained show that globally, in the period under analysis, the EU has increased its environmental efficiency which is consistent with the analysis of the indicators of the 2020 climate and energy package.info:eu-repo/semantics/publishedVersio
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