Patch Plate Materials Compatibility Assessment

Lunar dust proved to be a greater problem during the Apollo missions than was originally anticipated. The highly angular, charged dust particles stuck to seals, radiators, and visors; clogged mechanisms; and abraded space suits. As reported by Apollo 12 astronaut Pete Conrad "We must have had more than a hundred hours suited work with the same equipment, and the wear was not as bad on the training suits as it is on these flight suits in just the eight hours we were out.". Dust clinging to surfaces was also transport-ed into habitable spaces leading to lung and eye irritation of the astronauts. The Apollo astronauts were on the Lunar surface less than 24 hours and experienced many dust related problems. With the Artemis program, we are planning longer stays on the surface, with more activities that have the potential to put the astronauts and equipment in contact with greater quantities of Lunar dust. The success of these missions will depend on our understanding of material interactions with Lunar dust and the development of ways to mitigate dust effects in cases where exposure to dust will lead to failure of components, unacceptable loss of power or thermal control, unacceptable loss of visibility, or health issues. Through the Lunar Surface In-novation Initiative (LSII), we are initiating a Patch Plate Materials Compatibility Assessment project. The overall goal of the three year project is to develop passive approaches to mitigate Lunar dust adhesion to surfaces for technologies that are currently at TRL levels 2-3 to bring them to TRL level 5 through ground-based assessment, culminating in a demonstration flight experiment on a Commercial Lunar Payload Services (CLPS) lander in 2022-2023. This paper discusses the detailed technical objectives and approach for this project. References: Gaier, J.R. "The Effects of Lunar Dust on EVA Systems During the Apollo Missions," NASA/TM-2005-213610/REV1, (2005), Apollo 12 Technical Crew Debriefing, December 1, 1969, pp. 10-54

Does Homeownership Prolong the Duration of Unemployment?

We examine the effects of homeownership on individuals' unemployment durations. An unemployment spell can terminate with a job or with nonparticipation. The endogeneity of homeownership is addressed by estimating a full maximum likelihood function jointly modeling the competing hazards and the probability of being a homeowner. Unobserved factors contributing to the probability of being a homeowner are allowed to be correlated with unobservable heterogeneity in the hazard rates. Not controlling for ownership selection, there is neither a significant difference in the job-finding hazard nor in the nonparticipation hazard of unemployed owners and renters. If we jointly model the ownership selection, we find that unemployed homeowners are more likely to find a job than renters

From the mouths of social media users: A focus group study exploring the social casino gaming–online gambling link

Background and aims The potential link between social casino gaming and online gambling has raised considerable concerns among clinicians, researchers and policy makers. Unfortunately, however, there is a paucity of research examining this potential link, especially among young adults. This represents a significant gap given young adults are frequently exposed to and are players of social casino games. Methods To better understand the potential link between social casino games and online gambling, we conducted three focus groups (N = 30) at two large Canadian Universities with college students who were avid social media users (who are regularly exposed to social casino games). Results Many participants spontaneously mentioned that social casino games were a great opportunity to build gambling skills before playing for real money. Importantly, some participants expressed a belief that there is a direct progression from social casino gaming to online gambling. Conversely, others believed the transition to online gambling depended on a person’s personality, rather than mere exposure to social casino games. While many young adults in our focus groups felt immune to the effects of social casino games, there was a general consensus that social casino games may facilitate the transition to online gambling among younger teenagers (i.e., 12–14 yr olds), due to the ease of accessibility and early exposure. Discussion The results of the present research point to the need for more study on the effects of social casino gambling as well as a discussion concerning regulation of social casino games in order to minimize their potential risks

Reliable Bonding of Composite Laminates Using Reflowable Epoxy Resins

Epoxy matrix composites assembled with adhesives maximize the performance of aerospace structures, but the possibility of forming weak bonds requires the installation of redundant fasteners, which add weight and manufacturing cost. Co-cured joints (e.g. unitized composite structures) are immune to weak bonds because the uncured resin undergoes diffusion and mixing through the joint. A means of co-curing complex structures may reduce the need for redundant fasteners in bondlines. To this end, NASA started the AERoBOND project to develop novel joining materials to enable a secondary-co-cure assembly process. Aerospace epoxy resin systems reformulated with offset stoichiometry prevented the resin from advancing beyond the gel point during a conventional autoclave cure cycle up to 180 C. The offset resins were applied to the joining surfaces of laminate preforms as prepreg. Two surfaces with complimentary offset resins were joined using conventional secondary bonding techniques. Preliminary efforts have indicated that the resulting joint has no discernable interface and appears as a conventional co-cured laminate under optical magnification. This report will discuss the initial work performed regarding formulation of the epoxy resin system using calorimetry, rheology, and mechanical testing

Laser Surface Preparation for Adhesive Bonding of Ti-6Al-4V

Adhesively bonded structures are potentially lighter in weight than mechanically fastened ones, but existing surface treatments are often considered unreliable. Two main problems in achieving reproducible and durable adhesive bonds are surface contamination and variability in standard surface preparation techniques. In this work three surface pretreatments were compared: laser etching with and without grit blasting and conventional Pasa-Jell treatment. Ti-6Al-4V surfaces were characterized by contact angle goniometry, optical microscopy, and X-ray photoelectron spectroscopy (XPS). Laser -etching was found to produce clean surfaces with precisely controlled surface topographies and PETI-5 lap shear strengths and durabilities were equivalent to those produced with Pasa-Jell

The opposite of Dante's hell? The transfer of ideas for social housing at international congresses in the 1850s–1860s

With the advent of industrialization, the question of developing adequate housing for the emergent working classes became more pressing than before. Moreover, the problem of unhygienic houses in industrial cities did not stop at the borders of a particular nation-state; sometimes literally as pandemic diseases spread out 'transnationally'. It is not a coincidence that in the nineteenth century the number of international congresses on hygiene and social topics expanded substantially. However, the historiography about social policy in general and social housing in particular, has often focused on individual cases because of the different pace of industrial and urban development and is thus dominated by national perspectives. In this paper, I elaborate on transnational exchange processes and local adaptations and transformations. I focus on the transfer of the housing model of SOMCO in Mulhouse, (a French house building association) during social international congresses. I examine whether cross-national networking enabled and facilitated the implementation of ideas on the local scale. I will elaborate on the transmission and the local adaptation of the Mulhouse-model in Belgium. Convergences, divergences, and different factors that influenced the local transformations (personal choice, political situation, socioeconomic circumstances) will be taken into accoun

Shear Stress Sensing with Elastic Microfence Structures

In this work, elastic microfences were generated for the purpose of measuring shear forces acting on a wind tunnel model. The microfences were fabricated in a two part process involving laser ablation patterning to generate a template in a polymer film followed by soft lithography with a two-part silicone. Incorporation of a fluorescent dye was demonstrated as a method to enhance contrast between the sensing elements and the substrate. Sensing elements consisted of multiple microfences prepared at different orientations to enable determination of both shear force and directionality. Microfence arrays were integrated into an optical microscope with sub-micrometer resolution. Initial experiments were conducted on a flat plate wind tunnel model. Both image stabilization algorithms and digital image correlation were utilized to determine the amount of fence deflection as a result of airflow. Initial free jet experiments indicated that the microfences could be readily displaced and this displacement was recorded through the microscope

Strong interface-induced spin-orbit coupling in graphene on WS2

Interfacial interactions allow the electronic properties of graphene to be modified, as recently demonstrated by the appearance of satellite Dirac cones in the band structure of graphene on hexagonal boron nitride (hBN) substrates. Ongoing research strives to explore interfacial interactions in a broader class of materials in order to engineer targeted electronic properties. Here we show that at an interface with a tungsten disulfide (WS2) substrate, the strength of the spin-orbit interaction (SOI) in graphene is very strongly enhanced. The induced SOI leads to a pronounced low-temperature weak anti-localization (WAL) effect, from which we determine the spin-relaxation time. We find that spin-relaxation time in graphene is two-to-three orders of magnitude smaller on WS2 than on SiO2 or hBN, and that it is comparable to the intervalley scattering time. To interpret our findings we have performed first-principle electronic structure calculations, which both confirm that carriers in graphene-on-WS2 experience a strong SOI and allow us to extract a spin-dependent low-energy effective Hamiltonian. Our analysis further shows that the use of WS2 substrates opens a possible new route to access topological states of matter in graphene-based systems.Comment: Originally submitted version in compliance with editorial guidelines. Final version with expanded discussion of the relation between theory and experiments to be published in Nature Communication