Unmanned surface vehicle (USV) has witnessed a rapid growth in the recent decade and has been applied in various practical applications in both military and civilian domains. USVs can either be ...deployed as a single unit or multiple vehicles in a fleet to conduct ocean missions. Central to the control of USV and USV formations, path planning is the key technology that ensures the navigation safety by generating collision free trajectories. Compared with conventional path planning algorithms, the deep reinforcement learning (RL) based planning algorithms provides a new resolution by integrating a high-level artificial intelligence. This work investigates the application of deep reinforcement learning algorithms for USV and USV formation path planning with specific focus on a reliable obstacle avoidance in constrained maritime environments. For single USV planning, with the primary aim being to calculate a shortest collision avoiding path, the designed RL path planning algorithm is able to solve other complex issues such as the compliance with vehicle motion constraints. The USV formation maintenance algorithm is capable of calculating suitable paths for the formation and retain the formation shape robustly or vary shapes where necessary, which is promising to assist with the navigation in environments with cluttered obstacles. The developed three sets of algorithms are validated and tested in computer-based simulations and practical maritime environments extracted from real harbour areas in the UK.
Gas-sensing applications commonly use nanomaterials (NMs) because of their unique physicochemical properties, including a high surface-to-volume ratio, enormous number of active sites, controllable ...morphology, and potential for miniaturisation. NM-based gas sensors, as a noninvasive, real-time technique, are a promising candidate for monitoring human breath. This review focuses on NM-based gas sensors used for breath diagnosis. First we describe some representative biomarkers of diseases that are detectable in breath and requirements for breath sensors. Then we review electrical, optical and mass-sensitive gas sensors in terms of these performance requirements, together with describing the detection capability of these sensors for trace concentrations of biomarkers and their initial attempts to diagnose disease. Moreover, we discuss breath sensor platforms with a multivariable sensing system, wireless communication and breath sampling, essential for predictive, preventive, personalised, and participatory ("P4") medicine. Finally, we conclude with problems and challenges associated with the selectivity, humidity and validation of breath sensors. We hope that this article will inspire the development of high-performance gas sensors based on novel NMs.
Induction of the transcriptional repressor Bcl-6 in CD4+ T cells is critical for the differentiation of follicular helper T cells (TFH cells), which are essential for B cell-mediated immunity. In ...contrast, the transcription factor Blimp1 (encoded by Prdm1) inhibits TFH differentiation by antagonizing Bcl-6. Here we found that the transcription factor TCF-1 was essential for both the initiation of TFH differentiation and the effector function of differentiated TFH cells during acute viral infection. Mechanistically, TCF-1 bound directly to the Bcl6 promoter and Prdm1 5' regulatory regions, which promoted Bcl-6 expression but repressed Blimp1 expression. TCF-1-null TFH cells upregulated genes associated with non-TFH cell lineages. Thus, TCF-1 functions as an important hub upstream of the Bcl-6-Blimp1 axis to initiate and secure the differentiation of TFH cells during acute viral infection.
The Tazhong area is located in the hinterland of the Taklimakan Desert, where abundant hydrocarbon resources are contained in the deep Ordovician carbonate rocks. Great exploration results have been ...obtained in the Middle and Lower Ordovician Yingshan formation over recent years, and a large layered oil/gas field has been proven. The fluid properties of this reservoir are complicated, and it can be divided into condensate gas reservoir, volatile oil reservoir and oil reservoir in accordance with fluid component and PVT phase behavior. These reservoirs distribute in alternation horizontally, without apparent boundaries vertically. Based on the study and analysis on test, exploration and production data, it is believed that the diversity of fluid properties results from the multiphase uneven infusion action of oil and gas, especially the severity of gas cut at late stage: the reservoir suffered from severe gas cut became condensate gas reservoir, the one suffered from weak gas cut became volatile oil reservoir, and the one free from gas cut still keeps the original oil reservoir state. It is discovered through study that the strike-slip fault plays an important role in the occurrence of gas cut at late stage: it not only acted as the pathway of gas migration at late stage, but also had an important impact on the reformation of reservoir. The impact of reservoir nature on gas cut mainly finds expression in the difference of combination of reservoir space: the mutually connected large pore/cavity and fracture system was favorable for gas charge at late stage, where condensate gas reservoir was mostly formed; while the isolated pore/cavity where the tectoclase developed weakly was relatively sealed, was unfavorable for the sufficient infusion of natural gas at late stage, and usually keeps the original oil reservoir state or formed volatile oil reservoir. Based on the discussion to the factors that affect the severity of gas cut in the paleo-reservoir at late stage, this paper clarifies the accumulation mechanisms and controlling factors of different kinds of reservoirs, establishes the accumulation mode of 3 types of reservoirs, and this is very significant to the effective prediction of hydrocarbon distribution in the deep carbonate rocks of the Tazhong area.
Heterogeneous reactions associated with porous solid films are ubiquitous and play an important role in both nature and industrial processes. However, due to the no-slip boundary condition in ...pressure-driven flows, the interfacial mass transfer between the porous solid surface and the environment is largely limited to slow molecular diffusion, which severely hinders the enhancement of heterogeneous reaction kinetics. Herein, we report a hierarchical-structure-accelerated interfacial dynamic strategy to improve interfacial gas transfer on hierarchical conductive metal-organic framework (c-MOF) films. Hierarchical c-MOF films are synthesized via the in-situ transformation of insulating MOF film precursors using π-conjugated ligands and comprise both a nanoporous shell and hollow inner voids. The introduction of hollow structures in the c-MOF films enables an increase of gas permeability, thus enhancing the motion velocity of gas molecules toward the c-MOF film surface, which is more than 8.0-fold higher than that of bulk-type film. The c-MOF film-based chemiresistive sensor exhibits a faster response towards ammonia than other reported chemiresistive ammonia sensors at room temperature and a response speed 10 times faster than that of the bulk-type film.
Nowadays, detection of trace concentration gases is still challenging for portable sensors, especially for the low-cost and easily operated metal-oxide-semiconductor (MOX) gas sensors. In this paper, ...a widely applicable amplification circuit is designed and fabricated to evidently enhance the signal of the MOX sensors by adding a field effect transistor (FET) into the conventional circuits. By optimizing the FET parameters and the loading resistance, this amplification circuit enables the commercial Figaro TGS2602 toluene sensors response effectively to the highest permissive limit (0.26 ppm) of toluene in indoor air of cars, with the detection limit of ~0.1 ppm. Furthermore, this circuit can also make the commercial Hanwei MP502 acetone sensors and MQ3 ethanol sensors response to the 1-2-ppm acetone in breath of diabetes and 2-ppm ethanol for fast and effectively drinker driver screening. The mechanism is investigated to be the gate voltage induced resistance change of the FET, with the highest theoretically estimated and experimentally measured magnification factor of 5-6. This FET amplifier can effectively enable the ppm level commercial MOX sensors response to sub-ppm level gases, promising for MOX gas sensor integration and also for other kind of resistive sensors.
•BaTiO3 coatings were successfully sprayed by employing the HEPJet spraying system.•The average bond strength between the coating and substance was 42MPa.•The coating exhibits the piezoelectric with ...different frequencies at room temperature.
Plasma spraying technique enables to create layers with thickness in a millimeter range adhering to various substrates. The supersonic plasma spraying can spray the powders at acoustic speed, which can increase the coating density and improve the bond strength between the coating and substrate. In the present study, a BaTiO3 coating with good physical property and preliminary piezoelectric index was prepared by supersonic plasma spraying. The spraying process was carried out by a direct current gas-stabilized plasma gun, which was manufactured by the Science and Technology on Remanufacturing Laboratory. It was found that the high temperature could make the BaTiO3 possess the piezoelectric nature. The surface of the BaTiO3 coating was smooth and dense, and the mechanical bond existed between the substrate and the coating. The average bond strength and microhardness were 47.4MPa and 650HV0.1, respectively. The BaTiO3 phase changed from cubic to tetragonal phase in the course of supersonic plasma flame flow. About 25% (mol) BaTiO3 was decomposed into BaO and TiO2. The decomposition and original defects of the spraying coating could decrease its piezoelectric activity. The piezoelectric performance of the BaTiO3 coating was lower than that of the sintering ceramic, but obvious piezoelectricity existed in the sprayed BaTiO3 coating.
The long-term persistence of viral antigens drives virus-specific CD8 T cell exhaustion during chronic viral infection. Yet exhausted, CD8 T cells are still endowed with certain levels of effector ...function, by which they can keep viral replication in check in chronic infection. However, the regulatory factors involved in regulating the effector function of exhausted CD8 T cell are largely unknown. Using mouse model of chronic LCMV infection, we found that the deletion of transcription factor TCF-1 in LCMV-specific exhausted CD8 T cells led to the profound reduction in cytokine production and degranulation. Conversely, ectopic expression of TCF-1 or using agonist to activate TCF-1 activities promotes the effector function of exhausted CD8 T cells. Mechanistically, TCF-1 fuels the functionalities of exhausted CD8 T cells by promoting the expression of an array of key effector function-associated transcription regulators, including Foxo1, Zeb2, Id3, and Eomes. These results collectively indicate that targeting TCF-1 mediated transcriptional pathway may represent a promising immunotherapy strategy against chronic viral infections by reinvigorating the effector function of exhausted virus-specific CD8 T cells.
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