559 research outputs found
Overview of Carbon Dioxide Control Issues During International Space Station/Space Shuttle Joint Docked Operations
Crewed space vehicles have a common requirement to remove the carbon dioxide (CO2) created by the metabolic processes of the crew. The space shuttle [Space Transportation System (STS)] and International Space Station (ISS) each have systems in place that allow control and removal of CO2 from the habitable cabin environment. During periods in which the space shuttle is docked to the ISS, known as "joint docked operations," the space shuttle and ISS share a common atmosphere environment. During this period, an elevated amount of CO2 is produced through the combined metabolic activity of the STS and ISS crews. This elevated CO2 production, together with the large effective atmosphere created by collective volumes of the docked vehicles, creates a unique set of requirements for CO2 removal. This paper will describe individual CO2 control plans implemented by STS and ISS engineering teams, as well as the integrated plans used when both vehicles are docked. The paper will also discuss some of the issues and anomalies experienced by both engineering teams
Multimode step-index fibers as stress/strain sensors for large structural steel and concrete systems
Overview of International Space Station Carbon Dioxide Removal Assembly On-Orbit Operations and Performance
Controlling Carbon Dioxide (CO2) partial pressure in the habitable vehicle environment is a critical part of operations on the International Space Station (ISS). On the United States segment of ISS, CO2 levels are primarily controlled by the Carbon Dioxide Removal Assembly (CDRA). There are two CDRAs on ISS; one in the United States Laboratory module, and one in the Node3 module. CDRA has been through several significant operational issues, performance issues and subsequent re-design of various components, primarily involving the Desiccant Adsorbent Bed (DAB) assembly and Air Selector Valves (ASV). This paper will focus on significant operational and performance issues experienced by the CDRA team from 2008-2012
CaractĂ©risation des sols de la vallĂ©e rizicole de Tamra dans lâĂźle de Mar, Centre-Ouest du SĂ©nĂ©gal
Tamra est une vallĂ©e trĂšs sollicitĂ©e pour la culture du riz par les populations des quatre villages implantĂ©s dans lâĂźle de Mar. LâĂ©tude pĂ©dologique a Ă©tĂ© menĂ©e suivant trois toposĂ©quences transversales le long de la vallĂ©e. Les diffĂ©rents types de sols rencontrĂ©s dans ce milieu fluvio-marin sont disposĂ©s dâune maniĂšre quasi-concentrique autour de la vallĂ©e. Les sols sont affectĂ©s par le processus de salinisation et dâacidification. Les causes principales de lâavancĂ©e de ce biseau salĂ© le long de la vallĂ©e seraient liĂ©es Ă lâenvironnement climatique peu favorable qui sĂ©vit depuis plusieurs annĂ©es et qui sâexprime par des sĂ©cheresses rĂ©currentes. La texture sableuse de ces sols, Ă dominance de sables fins, et leur niveau topographique font que certains dâentre eux sont exceptionnellement inondĂ©s. Ainsi, la rĂ©alisation dâune carte dâaptitude culturale des sols sâimpose pour une meilleure utilisation des terres de la vallĂ©e de Tamra.Mots clĂ©s : Tamra, sols, fertilitĂ©, salinisation, acidification
Measurement of Condensation Heat Transfer and Pressure Drop for Zeotropic Mixture R-454C and its Components R-32 and R-1234yf in a Horizontal Microfin Tubes
This paper compares the condensation heat transfer and pressure drop for zeotropic refrigerant R454C and its individual components, R32 and R1234yf, in a horizontal microfin tube. The microfin tube has a 4 mm outer diameter, 0.18 mm wall thickness, and a surface area ratio of 1.56. HFOs and HFC/HFO blends like R454C have low global warming potential and can be alternatives to HFC refrigerants when retrofitting a system or producing new equipment. However, there is an additional mass transfer resistance present during phase change for a zeotropic mixture, which results in reduced heat transfer performance. Microfin tubes enhance heat transfer through multiple mechanisms: they increase the internal surface area of the tube, the fins drain condensate from the fin tip to the trough region, and they produce secondary flow structures. Presently, there is limited data of HFO/HFC mixtures in microfin tubes. Thus, experiments are conducted for complete condensation of R454C, R1234yf and R32 for saturation temperatures of 40, 50 and 60 °C and mass fluxes from 100 to 600kgmâ2sâ1. Experimental heat transfer and pressure drop measurements are compared to wellestablished correlations from the literature. Heat transfer enhancement factors and pressure drop penalty factors are calculated for each refrigerant
Enterprise Architecture Shapes Stakeholder Salience Influence on Enterprise Value-creation
Student research poster, LAI Annual Meeting, Dana Point, C
"Siding with the people" or "Occupying force"? Local perceptions of African Union and ECOWAS interventions in the Gambia
How do African citizens experience and evaluate African regional interÂventions? This reÂsearch report exaÂmines the case of The GamÂbia to assess local percepÂtions of the African Union and ECOWAS, particuÂlarly of their interÂventions in that country since 2016. It is the result of collaÂboraÂtive and empiriÂcally comprehenÂsive research carried out across the country in 2021/2022. We demonÂstrate that percepÂtions of the intervenÂtions in The Gambia are complex and diverge starkly, at times even contraÂdicting each other. We explain this comÂplexity as resulÂting from spatial, tempoÂral, and sociopoÂlitical factors that affect how these AfriÂcan regioÂnal interÂventions are (diffeÂrently) perceived
- âŠ