97 research outputs found
Shape Memory Alloys for Regulating TCS in Space (SMARTS): Validated Multiphysical Modeling and Design Optimization of Morphing Composite Radiators
No full textSean Nevin, Texas A&M University, USJoseph El-Ashkar, Texas A&M University, USCollette Gillaspie, Texas A&M University, USDarren Hartl, Texas A&M University, USICES103: Thermal and Environmental Control of Exploration Vehicles and HabitatsThe 51st International Conference on Environmental Systems was held in Saint Paul, Minnesota, US, on 10 July 2022 through 14 July 2022.Future human spaceflight missions are expected to require increased turndowns in the amount of heat rejected by thermal control systems as they adjust to variations in heat loads and the surrounding thermal environment to maintain crew cabin temperatures at a hospitable level. Current radiator systems can achieve a turndown ratio of 3:1; however, future missions are expected to demand ratios exceeding 6:1. Variable heat rejection space radiators are posed to provide this capability. The morphing radiator concept presented here accomplishes this via shape change, alternatively exposing low and high emissivity surfaces to the environment as passively thermally driven by shape memory alloys. Shape memory alloys are unique materials that use a thermally induced solid-solid phase transformation to generate strain and then fully recover it. This work covers the development and implementation of a modeling tool to simulate the morphing radiator behavior with ultimate application as a design tool. The model incorporates a multiphysics scheme to couple the thermal and geometric response of the radiator, which is required to capture radiation dependence on view factor. The fully developed model is then used to optimize radiator composite layup, SMA properties and number of wires to achieve full closure. The composite performance is further investigated to assess the optimal ply orientations through the use of black box surrogate modeling techniques such as efficient global optimization. This methodology efficiently searches through the design space for the computationally expensive finite element model. Full closure of the morphing radiator is essential to maximize turndown during cycling within operational temperatures of the thermal control system, and thus closed (cold state) aperture angle represents the primary objective of a design of experiments. Design study results shown provide a range of desirable shape memory alloy properties and wire quantity, which define the targets for upcoming prototyping and demonstration efforts
Parasitic copepods from Egyptian Red Sea fishes: Bomolochidae Claus, 1875
No full text© The Author(s) 2015
Open Access - This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The attached file is the published version of the article.NHM Repositor
Dragonfly: Detailed Thermal Control System Design
No full textKurt Gonter, Johns Hopkins University Applied Physics Laboratory, United StatesZhaojuan (Jane) He, Johns Hopkins University Applied Physics Laboratory, United StatesBruce Williams, Johns Hopkins University Applied Physics Laboratory, United StatesHui Liu, Johns Hopkins University Applied Physics Laboratory, United StatesAhmed Abir, Johns Hopkins University Applied Physics Laboratory, United StatesDahway Lin, Johns Hopkins University Applied Physics Laboratory, United StatesCollette Gillaspie, Johns Hopkins University Applied Physics Laboratory, United StatesMarisa Teti, Johns Hopkins University Applied Physics Laboratory, United StatesEvan Cosentino, Johns Hopkins University Applied Physics Laboratory, United StatesElisabeth Abel, Johns Hopkins University Applied Physics Laboratory, United StatesICES102: Thermal Control for Planetary and Small Body
Surface MissionsThe 54th International Conference on Environmental Systems was held in Prague, Czechia, on 13 July 2025 through 17 July 2025.Dragonfly is a NASA New Frontiers mission that will send a
rotorcraft lander to Titan, which has low gravity and a
dense 94K cryogenic nitrogen atmosphere. The lander Thermal
Control System (TCS) uses fans to circulate Titan
atmosphere internally, distributing heat from its MMRTG
power source to all internal components. In the last two
years, the system design has evolved significantly, with
special attention paid to improving the thermal control
system design in multiple areas to reach a CDR level of
maturity. Lander air inlet temperatures, previously
controlled via wall-mounted heat exchangers, are now
controlled using a composite external ducting system and
airflow diverter mechanism mounted to the lander belly. The
primary lander insulation material was updated to Solimide
16 after extensive testing, as Rohacell foam was found to
be prone to cracking and deformation. Additionally, to
increase system robustness on the launch pad after MMRTG
integration, a venting system was added to create a
flowpath between the lander and its external environment to
prevent battery overheating. This paper will provide an
overview of the matured thermal control system design and
will document key changes implemented since Mission PDR to
close the design with sufficient temperature margin, heat
leak margin, and control authority
Testing the vision: preschool settings as places for meeting, bonding and bridging
No full textThe OECD (2006 Starting Strong II: Early Childhood Education and Care. OECD Publishing: Paris) envisions early childhood education and care settings as meeting places for diverse social groups; places that build social capital. This vision was assessed in a comparison of three preschools types: full-fee paying, subsidised-fee and publicly funded. The social composition within each was examined and the connectedness of the children (n=472) who attended compared. Publicly funded preschools had more socially diverse populations. The quantity of social connectedness did not differ but children in publicly funded preschools described higher quality social relationships. Not all preschool settings are socially diverse but, where they are, the quality of relationships is highest. © 2010 The Author(s). Children & Societ
‘It’s not only what we say but what we do’: Pay inequalities and gendered workplace democracy in Argentinian worker cooperatives.
No full textIn a study conducted by the author in 2006 of five mixed-sex, worker-led cooperatives in Buenos
Aires, all of the workers in each of the coops were paid exactly the same. Five years later, only
two of the worker cooperatives – both dominated by women – came even close to maintaining
the same pay for everyone. The other three cooperatives, all dominated by male workers, had
instituted hierarchical pay scales which paralleled a concomitant decrease in workplace democracy.
An increase in pay inequities and a decrease in worker democracy went together; moreover, the
two paralleled an increasingly inhospitable workplace for women. This article addresses two,
interconnected, questions: How did this intertwining of pay and worker democracy happen, and
more specifically, how was this process gendered
Reading acts of narrative appropriation: four instances of fraudulent memoir
No full textPhDThis thesis examines acts of narrative appropriation, the telling of purportedly‘authentic’ life stories by those for whom the stories are not theirs to tell. This
misuse or subversion of genre - the discipline of historical writing and the category
of autobiography - becomes a means for cultural, social and political dissimulation,
and the analysis focuses both on the act: the event, trespass, or ‘theft’ of another’s
life story, and on the cultural meaning that this event reveals. These narrative acts
are approached theoretically through discussions of what it means to be an author, a
reader, and through the consideration of literary and social genre, category and form.
In exploring identities at particular risk of appropriation, this thesis shows how
fraudulent appropriated narratives affect our reading of the world, and in turn
influence our perception of already marginalized social groups. My primary
examples include prostitution ‘narratives’, Native North American ‘memoir,’ and
fraudulent Holocaust survivor ‘testimony,’ with each text providing decoded
evidence of ‘genre-bending’ exhibiting a social and political intent. These works
seek to be read as authentic personal narratives, as autobiography, and that is how
they have been presented to the reader. However, they are imposters – fictional tales
desiring the elevated status of historical authenticity and willing to bend the rules
and contracts of genre to achieve their end. Here the appearance of authenticity is
achieved through the use of cultural and social ‘myth,’ or perceptions of cultural
identity, and as such its fraudulent construction is first and foremost a social act,
with a social and economic motivation. As this thesis concludes, these texts are
most successful when their own political and social ideologies echo and confirm that
of the readership; when their subjects, the fraudulent ‘I’ at the center of the text is
also a performative elaboration of cultural belief
L'influence du stoïcisme sur le De Abstinentia de Porphyre
No full textLe traité De l’abstinence est écrit par Porphyre dans le but de convaincre son ami de revenir à la pratique du végétarisme, qu‟il a récemment abandonnée. Dans ce texte, l‟auteur présente une série d‟arguments anti-végétariens, qu‟il réfutera tout en défendant la pertinence de ce mode de vie pour le philosophe. Parmi les opposants, les stoïciens occupent une place importante, le troisième livre du traité leur étant presque entièrement consacré. En réfutant les arguments anti-végétariens des stoïciens, Porphyre développe ses positions avec un vocabulaire qu‟il leur emprunte. Ce faisant, il teinte son traité de l‟influence stoïcienne. Ce mémoire a pour objectif d‟analyser de quelle manière le dialogue entre Porphyre et les stoïciens influence l‟auteur du De abstinentia. L‟argument anti-végétarien attribué aux stoïciens consiste à dire qu‟il est impossible de demander à ce que les êtres humains épargnent la vie des animaux, puisque ceux-ci ne nous sont pas familiers (oikeion), du fait de leur absence de raison. Or, puisque dans la théorie stoïcienne la justice prend sa source dans les relations de familiarité qui lie les êtres rationnels entre eux, on ne peut considérer que la mise à mort des animaux dans le but de consommer leur chair est un acte injuste, voire impie, comme le soutient Porphyre. Les trois termes de ce débat feront chacun l‟objet d‟un chapitre : oikeiôsis, justice et logos. Ces trois notions permettront d‟approfondir la teneur du désaccord de Porphyre avec les stoïciens et de comprendre de quelle manière ce néoplatonicien se réapproprie le vocabulaire stoïcien pour le pousser à des conclusions qui sont conformes à sa métaphysique. On trouvera que derrière la question du végétarisme, c‟est le thème plus complexe du mode de vie qui anime le débat.The treatise On Abstinence is written by Porphyry in order to convince his friend to return to the practice of vegetarianism, which he recently abandoned. In this text, a series of anti-vegetarian arguments are presented, which the author refutes while defending the relevance of this way of life for the philosopher. Among the opponents, the Stoics have an important place, the third book of the treaty being almost entirely devoted to them. Refuting the anti-vegetarian arguments of the Stoics, Porphyry develops his positions with a vocabulary borrowed to them. In doing so, he gives his treatise a Stoic flavour. This dissertation aims to analyze how the dialogue between Porphyry and the Stoics influences the author of the De abstinentia. The anti-vegetarian argument attributed to the Stoics says that it is impossible to ask of human to spare the life of animals, since they are not rational and, thus, not appropriate (oikeion) to us. Because, in the Stoic‟s theory, justice is rooted in the relations of appropriation between rational beings, we could not say that killing animals to eat their flesh is unjust, or impious, like Porphyry argues. One chapter will be dedicated to each of the terms of this debate: oikeiôsis, justice and reason. These three notions will allow us to further the analysis of the disagreement of Porphyry towards the Stoics and to understand how this neoplatonic philosopher uses the Stoics vocabulary to pursue his own metaphysical goals. We will find that behind the question of vegetarianism lies the more complex theme of the way of life
An analysis of factors influencing the shortage of minorities in the teaching profession,1975-1990, 2003
No full textThe shortage of minority teachers has generated much concern among educators and professional organi-zations, such as the Carnegie Forum on Education, the National Education Association, the American Federation of Teachers, and the newly created Homes Group. This research sought to examine the literature pertaining to factors influencing the shortage. r.ority teachers in the teaching field. A preliminary baseline study of the literature relating to the shortage of minorities in the teaching field was conducted utilizing both manual and computerized literature searches. The universe of data studies was literature pertaining to the shortage of minority teachers. An in-depth study of the literature was performed utilizing eight variables, namely: 1. Salary 2. Career Advancement 3. Racial Composition of Teachers 4. Fringe Benefits 5. Bonuses 6. Continuous Testing of Teachers 7. Rural/Urban Working Environment 8. Funds for Professional Growth and Development An in-depth study of the literature in relationship to the variables constituted the major aspect of the research. Content analysis was the major research ap-proach utilized in this study. This approach was selected because it provided a systematic, objective and quanti�tative research technique for analyzing contents. Content analysis is a research technique for making replicable and valid inferences from data to their con-text, or a research technique for the objective, system-atic, and quantitative description of the manifest of communication. The results of this investigation supported the basic premise that the variables identified contribute to the shortage of minorities in the teaching profession
Attitudes of Tanzanian women towards marriage rituals, 1992
No full textThe purpose of this study is to investigate the attitudes of Tanzanian women towards marriage rituals. Data utilized came from three sources: personal interactive observations, the responses from focus discussion sessions and conversations conducted while the researcher was in Tanzania. Findings show that wedding rituals in contemporary, urban settings are a unique combination of traditional Tanzanian culture and aspects borrowed from outside influences. The study also looks at the impact of education, urbanization, occupation, ethnic group and religion on the attitudes of women living in a changing society
Selection bias is not a good reason for advising more than 5 years of adjuvant hormonal therapy for all patients with locally advanced prostate cancer treated with radiotherapy
No full text- …
