179 research outputs found
Minimizing Cr-evaporation from Balance of Plant Components by Utilizing Cost-Effective Alumina-Forming Austenitic Steels
A solid oxide fuel cell (SOFC) is a clean and efficient energy conversion device. The development of intermediate-temperature SOFCs has made it preferable to use metallic interconnects (MICs) to greatly reduce the cost and significantly increase the efficiency compared to ceramic interconnect materials. However, gaseous chromium species will evaporate from the chromium-containing layer formed on the surface of commonly used MICs and balance of plant (BoP) components. Volatile chromium species have been shown to form solid deposits which poison the cathodes of SOFCs, causing drastic cell performance degradation and thereby limiting commercialization. In order to alleviate the Cr poisoning and achieve long-term high performance of SOFC stacks, various Al2O3-forming austenitic (AFA) stainless steels applied at different temperatures are evaluated in this work. It is shown that on the AFAs, an alumina-based protective layer forms under high temperature that is invulnerable to water vapor effects and suppresses the diffusion of chromium and manganese which can prevent the generation of spinels on the alloy surface. The chromium (Cr) evaporation behavior of several different types of iron (Fe)-based AFA alloys and benchmark Cr2O3-forming Fe-based 310 and Ni-based 625 alloys was investigated for 500 h exposures at 800 °C to 900 °C in air with 10% H2O. The Cr evaporation rates from alumina-forming austenitic (AFA) alloys were ~5 to 35 times lower than that of the Cr2O3-forming alloys depending on alloy and temperature. The Cr evaporation behavior was correlated with extensive characterization of the chemistry and microstructure of the oxide scales, which also revealed a degree of quartz tube Si contamination during the test. Long-term oxidation kinetics were also assessed at 800 to 1000 °C for up to 10,000 h in air with 10% H2O to provide further guidance for SOFC BOP component alloy selection. Besides the lower Cr evaporation rates and better oxidation resistance of AFAs than benchmark alloys after short-term (500 h) operation, AFAs also possess the sturdy and compact alumina layer after a long-term operation (5000 h). The Cr evaporation and high-temperature oxidation behaviors of AFA alloys are systematically investigated in air + 10% H2O at 800 °C after various durations compared to commercial alloy 310S. The Cr evaporation rates of 310S are about 35 times higher than the AFA alloys after the entire test. Breakaway oxidation and spallation are observed on 310S after only one cycle, while the AFA alloys show high oxidation resistance. It is found that there are no voids formation, and the formation of a continuous alumina layer stays compact and stable during the entire test which greatly reduces the Cr 3 evaporation. The long-term oxidation and chromium evaporation behaviors of chromia-forming alloy 625 and AFA alloys were evaluated by transpiration tests, weight gain tests, X-ray diffraction technique, scanning electron microscopy coupled with energy dispersive X-ray analysis, and scanning transmission electron microscopy coupled with energy dispersive X-ray analysis. Results indicated that the 625 exhibits a 28-and 56-times higher evaporated Cr amounts than OC11 and OC11LZ, respectively. Different behaviors between OC11 and OC11LZ are resulted from the formed oxides scale variation during the long-term operation. Moreover, the effect of reactive elements on the long-term oxidation and chromium evaporation behaviors was discussed. Cr evaporation from BoP components in high-temperature environment could severely deteriorate the electrochemical performance of SOFC. Several methods were applied to evaluate the Cr evaporation rates of BoP components after 500 h exposure at 800 °C to 900 °C in air with 10% H2O. An optimal method was designed to exclude the effect of silicon (Si) deposits from quartz tube and sodium (Na) deposits from the sodium carbonate on the oxidation process and the chemical interaction between Cr gaseous species and alumina tube which could provide further quantitative correlation of the evaporated Cr species quantities and degradation rates of SOFC. Based on the great performance of AFAs after long-term operation, AFAs are assembled with Anode-supported cells (ASC) to investigate the the Cr deposition of anode-supported cell under a constant current density of 0.5 A cm−2 at 800 °C with AFA alloys compared with commercial alloys which was analyzed by the distribution of relaxation times (DRT) and different equivalent circuit model methods. The performance deterioration of ASCs was mainly attributed to the increased polarization resistances of oxygen surface exchange and diffusion processes in the cathode region. The superior performance of ASC coupled with AFA alloys was due to the formed continuous alumina layer which can vastly decrease the evaporated gaseous Cr species, thus alleviating the Cr poisoning on the cathode region
Learn and Transfer Knowledge of Preferred Assistance Strategies in Semi-autonomous Telemanipulation
Enabling robots to provide effective assistance yet still accommodating the
operator's commands for telemanipulation of an object is very challenging
because robot's assistive action is not always intuitive for human operators
and human behaviors and preferences are sometimes ambiguous for the robot to
interpret. Although various assistance approaches are being developed to
improve the control quality from different optimization perspectives, the
problem still remains in determining the appropriate approach that satisfies
the fine motion constraints for the telemanipulation task and preference of the
operator. To address these problems, we developed a novel preference-aware
assistance knowledge learning approach. An assistance preference model learns
what assistance is preferred by a human, and a stagewise model updating method
ensures the learning stability while dealing with the ambiguity of human
preference data. Such a preference-aware assistance knowledge enables a
teleoperated robot hand to provide more active yet preferred assistance toward
manipulation success. We also developed knowledge transfer methods to transfer
the preference knowledge across different robot hand structures to avoid
extensive robot-specific training. Experiments to telemanipulate a 3-finger
hand and 2-finger hand, respectively, to use, move, and hand over a cup have
been conducted. Results demonstrated that the methods enabled the robots to
effectively learn the preference knowledge and allowed knowledge transfer
between robots with less training effort
Improvements on Recommender System based on Mathematical Principles
In this article, we will research the Recommender System's implementation
about how it works and the algorithms used. We will explain the Recommender
System's algorithms based on mathematical principles, and find feasible methods
for improvements. The algorithms based on probability have its significance in
Recommender System, we will describe how they help to increase the accuracy and
speed of the algorithms. Both the weakness and the strength of two different
mathematical distance used to describe the similarity will be detailed
illustrated in this article
MetaGPT: Meta Programming for Multi-Agent Collaborative Framework
Recently, remarkable progress has been made in automated task-solving through
the use of multi-agents driven by large language models (LLMs). However,
existing works primarily focuses on simple tasks lacking exploration and
investigation in complicated tasks mainly due to the hallucination problem.
This kind of hallucination gets amplified infinitely as multiple intelligent
agents interact with each other, resulting in failures when tackling
complicated problems.Therefore, we introduce MetaGPT, an innovative framework
that infuses effective human workflows as a meta programming approach into
LLM-driven multi-agent collaboration. In particular, MetaGPT first encodes
Standardized Operating Procedures (SOPs) into prompts, fostering structured
coordination. And then, it further mandates modular outputs, bestowing agents
with domain expertise paralleling human professionals to validate outputs and
reduce compounded errors. In this way, MetaGPT leverages the assembly line work
model to assign diverse roles to various agents, thus establishing a framework
that can effectively and cohesively deconstruct complex multi-agent
collaborative problems. Our experiments conducted on collaborative software
engineering tasks illustrate MetaGPT's capability in producing comprehensive
solutions with higher coherence relative to existing conversational and
chat-based multi-agent systems. This underscores the potential of incorporating
human domain knowledge into multi-agents, thus opening up novel avenues for
grappling with intricate real-world challenges. The GitHub repository of this
project is made publicly available on: https://github.com/geekan/MetaGP
Mechanisms of action and synergetic formulas of plant-based natural compounds from traditional Chinese medicine for managing osteoporosis: a literature review
Osteoporosis (OP) is a systemic skeletal disease prevalent in older adults, characterized by substantial bone loss and deterioration of microstructure, resulting in heightened bone fragility and risk of fracture. Traditional Chinese Medicine (TCM) herbs have been widely employed in OP treatment owing to their advantages, such as good tolerance, low toxicity, high efficiency, and minimal adverse reactions. Increasing evidence also reveals that many plant-based compounds (or secondary metabolites) from these TCM formulas, such as resveratrol, naringin, and ginsenoside, have demonstrated beneficial effects in reducing the risk of OP. Nonetheless, the comprehensive roles of these natural products in OP have not been thoroughly clarified, impeding the development of synergistic formulas for optimal OP treatment. In this review, we sum up the pathological mechanisms of OP based on evidence from basic and clinical research; emphasis is placed on the in vitro and preclinical in vivo evidence-based anti-OP mechanisms of TCM formulas and their chemically active plant constituents, especially their effects on imbalanced bone homeostasis regulated by osteoblasts (responsible for bone formation), osteoclasts (responsible for bone resorption), bone marrow mesenchymal stem cells as well as bone microstructure, angiogenesis, and immune system. Furthermore, we prospectively discuss the combinatory ingredients from natural products from these TCM formulas. Our goal is to improve comprehension of the pharmacological mechanisms of TCM formulas and their chemically active constituents, which could inform the development of new strategies for managing OP
Doppler Wind Lidar From UV to NIR: A Review With Case Study Examples
Doppler wind lidar (DWL) uses the optical Doppler effect to measure atmospheric wind speed with high spatial-temporal resolution and long detection range and has been widely applied in scientific research and engineering applications. With the development of related technology, especially laser and detector technology, the performance of the DWL has significantly improved for the past few decades. DWL utilizes different principles and different tracers to sense the wind speed from the ground to the mesosphere, which leads to the difference in choosing the laser working wavelength. This article will review the working wavelength consideration of DWL, and typical DWLs will present from ultraviolet to near-infrared, after which three typical applications will be shown
MyD88-dependent, superoxide-initiated inflammation is necessary for flow-mediated inward remodeling of conduit arteries
Vascular remodeling normalizes abnormal hemodynamic stresses through structural changes affecting vessel size and wall thickness. We investigated the role of inflammation in flow-mediated vascular remodeling using a murine model of partial outflow reduction without flow cessation or neointima formation. Common carotid arteries decreased in size after ipsilateral external carotid artery ligation in wild-type mice, but not in myeloid differentiation protein-88 (MyD88)–deficient mice. Inward remodeling was associated with MyD88-dependent and superoxide-initiated cytokine and chemokine production, as well as transient adventitial macrophage accumulation and activation. Macrophage depletion prevented flow-mediated inward vascular remodeling. Expression of MyD88 by intrinsic vascular cells was necessary for cytokine and chemokine production and changes in vessel size, whereas MyD88 expression by bone marrow–derived cells was obligatory for changes in vessel size. We conclude that there are at least two distinct roles for MyD88 in flow-mediated inward remodeling of conduit arteries. Our findings suggest that inflammation is necessary for vascular adaptation to changes in hemodynamic forces
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