309 research outputs found
Ni-Doped Sr\u3csub\u3e2\u3c/sub\u3eFe\u3csub\u3e1.5\u3c/sub\u3eMo\u3csub\u3e0.5\u3c/sub\u3eO\u3csub\u3e6-δ\u3c/sub\u3e as Anode Materials for Solid Oxide Fuel Cells
10% Ni-doped Sr2Fe1.5Mo0.5O6-δ with A-site deficiency is prepared to induce in situ precipitation of B-site metals under anode conditions in solid oxide fuel cells. XRD, SEM and TEM results show that a significant amount of nano-sized Ni-Fe alloy metal phase has precipitated out from Sr1.9Fe1.4Ni0.1Mo0.5O6-δ upon reduction at 800◦C in H2. The conductivity of the reduced composite reaches 29 S cm−1 at 800◦C in H2. Furthermore, fuel cell performance of the composite anode Sr1.9Fe1.4Ni0.1Mo0.5O6-δ-SDC is investigated using H2 as fuel and ambient air as oxidant with La0.8Sr0.2Ga0.87Mg0.13O3 electrolyte and La0.6Sr0.4Co0.2Fe0.8O3 cathode. The cell peak power density reaches 968 mW cm−2 at 800◦C and the voltage is relatively stable under a constant current load of 0.54 A cm−2. After 5 redox cycles of the anode at 800◦C, the fuel cell performance doesn’t suffer any degradation, indicating good redox stability of Sr1.9Fe1.4Ni0.1Mo0.5O6-δ. Peak power density of 227 mW cm−2 was also obtained when propane is used as fuel. These results indicate that a self-generated metal-ceramic composite can been successfully derived from Sr2Fe1.5Mo0.5O6-δ by compositional modifications and Sr1.9Fe1.4Ni0.1Mo0.5O6-δ is a very promising solid oxide fuel cell anode material with enhanced catalytic activity and inherited good redox stability from the parent ceramic material
La\u3csub\u3e0.7\u3c/sub\u3eSr\u3csub\u3e0.3\u3c/sub\u3eFe\u3csub\u3e0.7\u3c/sub\u3eGa\u3csub\u3e0.3\u3c/sub\u3eO\u3csub\u3e3-δ\u3c/sub\u3e as Electrode Material for a Symmetrical Solid Oxide Fuel Cell
In this research, La0.7Sr0.3Fe0.7Ga0.3O3−δ (LSFG) perovskite oxide was successfully prepared using a microwave-assisted combustion method, and employed as both anode and cathode in symmetrical solid oxide fuel cells. A maximum power density of 489 mW cm−2 was achieved at 800 °C with wet H2 as the fuel and ambient air as the oxidant in a single cell with the configuration LSFG|La0.8Sr0.2Ga0.83Mg0.17O3−δ|LSFG. Furthermore, the cells demonstrated good stability in H2 and acceptable sulfur tolerance
Edge Accelerated Robot Navigation with Hierarchical Motion Planning
Low-cost autonomous robots suffer from limited onboard computing power,
resulting in excessive computation time when navigating in cluttered
environments. This paper presents Edge Accelerated Robot Navigation, or EARN
for short, to achieve real-time collision avoidance by adopting hierarchical
motion planning (HMP). In contrast to existing local or edge motion planning
solutions that ignore the interdependency between low-level motion planning and
high-level resource allocation, EARN adopts model predictive switching (MPS)
that maximizes the expected switching gain w.r.t. robot states and actions
under computation and communication resource constraints. As such, each robot
can dynamically switch between a point-mass motion planner executed locally to
guarantee safety (e.g., path-following) and a full-shape motion planner
executed non-locally to guarantee efficiency (e.g., overtaking). The crux to
EARN is a two-time scale integrated decision-planning algorithm based on
bilevel mixed-integer optimization, and a fast conditional collision avoidance
algorithm based on penalty dual decomposition. We validate the performance of
EARN in indoor simulation, outdoor simulation, and real-world environments.
Experiments show that EARN achieves significantly smaller navigation time and
collision ratios than state-of-the-art navigation approaches.Comment: 12 pages, 14 figures, 1 table, submitted to IEEE for possible
publicatio
A note on control of a class of discrete-time stochastic systems with distributed delays and nonlinear disturbances
The official published version of this article can be found at the link below.This paper is concerned with the state feedback control problem for a class of discrete-time stochastic systems involving sector nonlinearities and mixed time-delays. The mixed time-delays comprise both discrete and distributed delays, and the sector nonlinearities appear in the system states and all delayed states. The distributed time-delays in the discrete-time domain are first defined and then a special matrix inequality is developed to handle the distributed time-delays within an algebraic framework. An effective linear matrix inequality (LMI) approach is proposed to design the state feedback controllers such that, for all admissible nonlinearities and time-delays, the overall closed-loop system is asymptotically stable in the mean square sense. Sufficient conditions are established for the nonlinear stochastic time-delay systems to be asymptotically stable in the mean square sense, and then the explicit expression of the desired controller gains is derived. A numerical example is provided to show the usefulness and effectiveness of the proposed design method.This work was supported in part by the Engineering and Physical Sciences Research Council (EPSRC) of the U.K. under Grant GR/S27658/01, the Royal Society of the U.K., the National Natural Science Foundation of China under Grants 60774073 and 60974030, the National 973 Program of China under Grant 2009CB320600, and the Alexander von Humboldt Foundation of Germany
Rethinking the Number of Shots in Robust Model-Agnostic Meta-Learning
Robust Model-Agnostic Meta-Learning (MAML) is usually adopted to train a
meta-model which may fast adapt to novel classes with only a few exemplars and
meanwhile remain robust to adversarial attacks. The conventional solution for
robust MAML is to introduce robustness-promoting regularization during
meta-training stage. With such a regularization, previous robust MAML methods
simply follow the typical MAML practice that the number of training shots
should match with the number of test shots to achieve an optimal adaptation
performance. However, although the robustness can be largely improved, previous
methods sacrifice clean accuracy a lot. In this paper, we observe that
introducing robustness-promoting regularization into MAML reduces the intrinsic
dimension of clean sample features, which results in a lower capacity of clean
representations. This may explain why the clean accuracy of previous robust
MAML methods drops severely. Based on this observation, we propose a simple
strategy, i.e., increasing the number of training shots, to mitigate the loss
of intrinsic dimension caused by robustness-promoting regularization. Though
simple, our method remarkably improves the clean accuracy of MAML without much
loss of robustness, producing a robust yet accurate model. Extensive
experiments demonstrate that our method outperforms prior arts in achieving a
better trade-off between accuracy and robustness. Besides, we observe that our
method is less sensitive to the number of fine-tuning steps during
meta-training, which allows for a reduced number of fine-tuning steps to
improve training efficiency
Salt-Enhanced Reproductive Development of Suaeda salsa L. Coincided With Ion Transporter Gene Upregulation in Flowers and Increased Pollen K+ Content
Halophytes are adapted to saline environments and demonstrate optimal reproductive growth under high salinity. To gain insight into the salt tolerance mechanism and effects of salinity in the halophyte Suaeda salsa, the number of flowers and seeds, seed size, anther development, ion content, and flower transcript profiles, as well as the relative expression levels of genes involved in ion transport, were analyzed in S. salsa plants treated with 0 or 200 mM NaCl. The seed size, flower number, seed number per leaf axil, and anther fertility were all significantly increased by 200 mM NaCl treatment. The Na+ and Cl− contents in the leaves, stems, and pollen of NaCl-treated plants were all markedly higher, and the K+ content in the leaves and stems was significantly lower, than those in untreated control plants. By contrast, the K+ content in pollen grains did not decrease, but rather increased, upon NaCl treatment. Genes related to Na+, K+ and, Cl− transport, such as SOS1, KEA, AKT1, NHX1, and CHX, showed increased expression in the flowers of NaCl-treated plants. These results suggest that ionic homeostasis in reproductive organs, especially in pollen grains under salt-treated conditions, involves increased expression of ion transport-related genes
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