scholarly journals Review of Plasma-Induced Hall Thruster Erosion

2020 ◽  
Vol 10 (11) ◽  
pp. 3775 ◽  
Author(s):  
Nathan P. Brown ◽  
Mitchell L. R. Walker
Keyword(s):  
Computational Models ◽  
High Efficiency ◽  
Mitigation Strategies ◽  
Hall Thruster ◽  
The Past ◽  
Plasma Sputtering ◽  
Plasma Thruster ◽  
Material Physics ◽  
Erosion Mitigation ◽  
Experimental Findings

The Hall thruster is a high-efficiency spacecraft propulsion device that utilizes plasma to generate thrust. The most common variant of the Hall thruster is the stationary plasma thruster (SPT). Erosion of the SPT discharge chamber wall by plasma sputtering degrades thruster performance and ultimately ends thruster life. Many efforts over the past few decades have endeavored to understand wall erosion so that novel thrusters can be designed to operate for the thousands of hours required by many missions. However, due to the challenges presented by the plasma and material physics associated with erosion, a complete understanding has thus far eluded researchers. Sputtering rates are not well quantified, erosion features remain unexplained, and computational models are not yet predictive. This article reviews the physics of plasma-induced SPT erosion, highlights important experimental findings, provides an overview of modeling efforts, and discusses erosion mitigation strategies.

The Impact of Abstraction and Fidelity Levels on the Usefulness of Early System Functional Models

2016 ◽  
Author(s):  
Sean C. Hunter ◽  
David C. Jensen ◽  
Irem Y. Tumer ◽  
Christopher Hoyle
Keyword(s):  
Failure Analysis ◽  
Computational Models ◽  
Mitigation Strategies ◽  
Design Stage ◽  
Levels Of Abstraction ◽  
Early Design Stage ◽  
Complex Engineered Systems ◽  
Engineered Systems ◽  
Experimental Findings ◽  
The Impact

For many complex engineered systems, a risk informed approach to design is critical to ensure both robust safety and system reliability. Early identification of failure paths in complex systems can greatly reduce the costs and risks absorbed by a project in future failure mitigation strategies. By exploring the functional effect of potential failures, designers can identify preferred architectures and technologies prior to acquiring specific knowledge of detailed physical system forms and behaviors. Early design-stage failure analysis is enabled by model-based design, with several research methodologies having been developed to support this design stage analysis through the use of computational models. The abstraction necessary for implementation at the design stage, however, leads to challenges in validating the analysis results presented by these models. This paper describes initial work on the comparison of models at varying levels of abstraction with results obtained on an experimental testbed in an effort to validate a function-based failure analysis method. Specifically, the potential functional losses of a simple rover vehicle are compared with experimental findings of similar failure scenarios. Expected results of the validation procedure suggest that a model’s validity and quality are a function of the depth to which functional details are described.

scholarly journals Analgesia for Sheep in Commercial Production: Where to Next?

Animals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 1127
Author(s):  
Alison Small ◽  
Andrew David Fisher ◽  
Caroline Lee ◽  
Ian Colditz
Keyword(s):  
Research Effort ◽  
Mitigation Strategies ◽  
Worth Living ◽  
Life Worth Living ◽  
The Past ◽  
Considerable Research ◽  
Husbandry Practices ◽  
Industry Practice ◽  
Successful Launch ◽  
Inflammatory Drugs

Increasing societal and customer pressure to provide animals with ‘a life worth living’ continues to apply pressure on livestock production industries to alleviate pain associated with husbandry practices, injury and illness. Over the past 15–20 years, there has been considerable research effort to understand and develop mitigation strategies for painful husbandry procedures in sheep, leading to the successful launch of analgesic approaches specific to sheep in a number of countries. However, even with multi-modal approaches to analgesia, using both local anaesthetic and non-steroidal anti-inflammatory drugs (NSAID), pain is not obliterated, and the challenge of pain mitigation and phasing out of painful husbandry practices remains. It is timely to review and reflect on progress to date in order to strategically focus on the most important challenges, and the avenues which offer the greatest potential to be incorporated into industry practice in a process of continuous improvement. A structured, systematic literature search was carried out, incorporating peer-reviewed scientific literature in the period 2000–2019. An enormous volume of research is underway, testament to the fact that we have not solved the pain and analgesia challenge for any species, including our own. This review has highlighted a number of potential areas for further research.

scholarly journals The first 10 years of the international coordination network for standards in systems and synthetic biology (COMBINE)

2020 ◽  
Vol 17 (2-3) ◽  
Author(s):  
Dagmar Waltemath ◽  
Martin Golebiewski ◽  
Michael L Blinov ◽  
Padraig Gleeson ◽  
Henning Hermjakob ◽  
...  
Keyword(s):  
Synthetic Biology ◽  
Data Model ◽  
Computational Models ◽  
Life Sciences ◽  
The Past ◽  
Challenges And Opportunities ◽  
Stakeholder Workshop ◽  
Software Engineers ◽  
Future Work ◽  
Modeling In Biology

AbstractThis paper presents a report on outcomes of the 10th Computational Modeling in Biology Network (COMBINE) meeting that was held in Heidelberg, Germany, in July of 2019. The annual event brings together researchers, biocurators and software engineers to present recent results and discuss future work in the area of standards for systems and synthetic biology. The COMBINE initiative coordinates the development of various community standards and formats for computational models in the life sciences. Over the past 10 years, COMBINE has brought together standard communities that have further developed and harmonized their standards for better interoperability of models and data. COMBINE 2019 was co-located with a stakeholder workshop of the European EU-STANDS4PM initiative that aims at harmonized data and model standardization for in silico models in the field of personalized medicine, as well as with the FAIRDOM PALs meeting to discuss findable, accessible, interoperable and reusable (FAIR) data sharing. This report briefly describes the work discussed in invited and contributed talks as well as during breakout sessions. It also highlights recent advancements in data, model, and annotation standardization efforts. Finally, this report concludes with some challenges and opportunities that this community will face during the next 10 years.

scholarly journals Urban Risks and Resilience

2021 ◽  
pp. 197-211
Author(s):  
Susan L. Cutter
Keyword(s):  
Adverse Events ◽  
Case Studies ◽  
Mitigation Strategies ◽  
Urban Resilience ◽  
Building Capacity ◽  
Urban Informatics ◽  
The Past ◽  
End Point ◽  
Point Versus

AbstractThe resilience concept has become more significant in the past decade as a means for understanding how cities prepare and plan for, absorb, recover from, and more successfully adapt to adverse events. Definitional differences—resilience as an outcome or end-point versus resilience as a process of building capacity—dominate the literature. Lagging behind are efforts to systematically measure resilience to produce a baseline and subsequent monitoring, in order to gauge what, where, and how intervention or mitigation strategies would strengthen or weaken urban resilience. The chapter reviews research and practitioner attempts to develop urban informatics for resilience and provides selected case studies of cities as exemplars.

scholarly journals Evolution of word meanings through metaphorical mapping: Systematicity over the past millennium.

2018 ◽  
Author(s):  
Yang Xu ◽  
Barbara Claire Malt ◽  
Mahesh Srinivasan
Keyword(s):  
Large Scale ◽  
Computational Models ◽  
Compact Set ◽  
Large Set ◽  
Word Meanings ◽  
The Past ◽  
History Of ◽  
Cognitive Principles ◽  
Metaphorical Mapping ◽  
Past Millennium

One way that languages are able to communicate a potentially infinite set of ideas through a finite lexicon is by compressing emerging meanings into words, such that over time, individual words come to express multiple, related senses of meaning. We propose that overarching communicative and cognitive pressures have created systematic directionality in how new metaphorical senses have developed from existing word senses over the history of English. Given a large set of pairs of semantic domains, we used computational models to test which domains have been more commonly the starting points (source domains) and which the ending points (target domains) of metaphorical mappings over the past millennium. We found that a compact set of variables, including externality, embodiment, and valence, explain directionality in the majority of about 5000 metaphorical mappings recorded over the past 1100 years. These results provide the first large-scale historical evidence that metaphorical mapping is systematic, and driven by measurable communicative and cognitive principles.

Experimenting on the past: a case study on changing analysability in English ly-adverbs

2017 ◽  
Vol 21 (2) ◽  
pp. 317-340 ◽  
Author(s):  
HENDRIK DE SMET ◽  
FREEK VAN DE VELDE
Keyword(s):  
Negative Correlation ◽  
Historical Data ◽  
Frequency Change ◽  
Data Sets ◽  
The Past ◽  
Analogous Composition ◽  
Using Data ◽  
Complex Words ◽  
Experimental Findings

While it is undoubtedly true that historical data do not lend themselves well to the reproduction of experimental findings, the availability of increasingly extensive data sets has brought some experimenting within practical reach. This means that certain predictions based on a combination of synchronic observations and uniformitarian thinking are now testable. Synchronic evidence shows a negative correlation between analysability in morphologically complex words and various measures of frequency. It is therefore expected that when the frequency of morphologically complex items changes, their analysability will change along with this. If analysability decreases, this should in turn be reflected in decreasing sensitivity to priming by items with analogous composition. The latter prediction is in principle testable on diachronic data, offering a way of verifying the diachronic effect of frequency change on analysability. In this spirit, the present article examines the relation between changing frequency and priming sensitivity, as a proxy to analysability. This is done for a sample of 250 English ly-adverbs, such as roughly, blindly, publicly, etc. over the period 1950–2005, using data from the Hansard Corpus. Some of the expected relations between frequency and analysability can be shown to hold, albeit with great variation across lexical items. At the same time, much of the variation in our measure of analysability cannot be accounted for by frequency or frequency change alone.

scholarly journals TACO and TRALI: biology, risk factors, and prevention strategies

Hematology ◽  
2018 ◽  
Vol 2018 (1) ◽  
pp. 585-594 ◽  
Author(s):  
Nareg Roubinian
Keyword(s):  
Risk Factors ◽  
Mitigation Strategies ◽  
Blood Component ◽  
Patient Blood Management ◽  
Blood Management ◽  
Prevention Strategies ◽  
In Vivo Models ◽  
The Past ◽  
Circulatory Overload

AbstractTransfusion-related acute lung injury (TRALI) and transfusion-associated circulatory overload (TACO) are the leading causes of transfusion-related morbidity and mortality. These adverse events are characterized by acute pulmonary edema within 6 hours of a blood transfusion and have historically been difficult to study due to underrecognition and nonspecific diagnostic criteria. However, in the past decade, in vivo models and clinical studies utilizing active surveillance have advanced our understanding of their epidemiology and pathogenesis. With the adoption of mitigation strategies and patient blood management, the incidence of TRALI and TACO has decreased. Continued research to prevent and treat these severe cardiopulmonary events is focused on both the blood component and the transfusion recipient.

Impending Collision Judgment from an Egocentric Perspective in Real and Virtual Environments: A Review

Perception ◽  
2019 ◽  
Vol 48 (9) ◽  
pp. 769-795 ◽  
Author(s):  
Ilja T. Feldstein
Keyword(s):  
Virtual Environments ◽  
Observation Time ◽  
Field Of View ◽  
Spatial Distance ◽  
Driving Experience ◽  
Factors Affecting ◽  
The Past ◽  
Technical Factors ◽  
Potential Factors ◽  
Experimental Findings

The human egocentric perception of approaching objects and the related perceptual processes have been of interest to researchers for several decades. This article gives a literature review on numerous studies that investigated the phenomenon when an object approaches an observer (or the other way around) with the goal to single out factors that influence the perceptual process. A taxonomy of metrics is followed by a breakdown of different experimental measurement methods. Thereinafter, potential factors affecting the judgment of approaching objects are compiled and debated while divided into human factors (e.g., gender, age, and driving experience), compositional factors (e.g., approaching velocity, spatial distance, and observation time), and technical factors (e.g., field of view, stereoscopy, and display contrast). Experimental findings are collated, juxtaposed, and critically discussed. With virtual-reality devices having taken a tremendous developmental leap forward in the past few years, they have been able to gain ground in experimental research. Therefore, special attention in this article is also given to the perception of approaching objects in virtual environments and put in contrast to the perception in reality.

scholarly journals The Mt John University Observatory search for Earth-mass planets in the habitable zone of α Centauri

2014 ◽  
Vol 14 (2) ◽  
pp. 305-312 ◽  
Author(s):  
Michael Endl ◽  
Christoph Bergmann ◽  
John Hearnshaw ◽  
Stuart I. Barnes ◽  
Robert A. Wittenmyer ◽  
...  
Keyword(s):  
High Efficiency ◽  
Detection Sensitivity ◽  
Habitable Zone ◽  
Echelle Spectrograph ◽  
Planet Detection ◽  
The Past ◽  
Temporal Sampling ◽  
Habitable Zones ◽  
Low Mass ◽  
Advanced Version

AbstractThe ‘holy grail’ in planet hunting is the detection of an Earth-analogue: a planet with similar mass as the Earth and an orbit inside the habitable zone. If we can find such an Earth-analogue around one of the stars in the immediate solar neighbourhood, we could potentially even study it in such great detail to address the question of its potential habitability. Several groups have focused their planet detection efforts on the nearest stars. Our team is currently performing an intensive observing campaign on the α Centauri system using the High Efficiency and Resolution Canterbury University Large Échelle Spectrograph (Hercules) at the 1 m McLellan telescope at Mt John University Observatory in New Zealand. The goal of our project is to obtain such a large number of radial velocity (RV) measurements with sufficiently high temporal sampling to become sensitive to signals of Earth-mass planets in the habitable zones of the two stars in this binary system. Over the past few years, we have collected more than 45 000 spectra for both stars combined. These data are currently processed by an advanced version of our RV reduction pipeline, which eliminates the effect of spectral cross-contamination. Here we present simulations of the expected detection sensitivity to low-mass planets in the habitable zone by the Hercules programme for various noise levels. We also discuss our expected sensitivity to the purported Earth-mass planet in a 3.24-day orbit announced by Dumusque et al. (2012).

The LAJ Cycle: A New Combined-Cycle Fossil Fuel Power System

2002 ◽  
Author(s):  
Roddie R. Judkins ◽  
Timothy R. Armstrong ◽  
Solomon D. Labinov
Keyword(s):  
Fuel Cells ◽  
Natural Gas ◽  
Power System ◽  
Fossil Fuel ◽  
High Efficiency ◽  
National Laboratory ◽  
Combined Cycle ◽  
Mitigation Strategies ◽  
Model Calculations ◽  
Oak Ridge

Oak Ridge National Laboratory (ORNL) has developed a novel system for combined-cycle power generation, called the LAJ cycle. This system could serve as a basis for the development of a new generation of high-efficiency combined cycles. In one of several possible configurations of the new combined-cycle fossil fuel power system, natural gas enters the system at 4.0 MPa and about 300 K, is heated and reformed, and is transferred to a turbine at 4.0 MPa and 1200 K. The gas expands in the turbine to 0.6 MPa and 800 K, and then flows successively to heat exchangers and a condenser-separator, after which it is separated into two gas streams, one containing principally CO with some CH4 and water vapor and the other containing pure H2. The CO and H2 flow to separate fuel cells and undergo electrochemical oxidation with the concomitant production of electricity. Separate streams of water and carbon dioxide (CO2) are produced, making this cycle compatible with carbon mitigation strategies based on sequestration. Model calculations indicate combined-cycle efficiencies greater than 70% based on the lower heating value of natural gas. The high efficiencies realized result from a combination of the high-pressure natural gas reformate expansion and the highly efficient CO and H2 fuel cells. Most of the power derives from the fuel cells in the system.

Sign in / Sign up

Export Citation Format

Share Document