Foam Core Shielding for Spacecraft

A foam core shield (FCS) system is now being developed to supplant multilayer insulation (MLI) systems heretofore installed on spacecraft for thermal management and protection against meteoroid impacts. A typical FCS system consists of a core sandwiched between a face sheet and a back sheet. The core can consist of any of a variety of low-to-medium-density polymeric or inorganic foams chosen to satisfy application-specific requirements regarding heat transfer and temperature. The face sheet serves to shock and thereby shatter incident meteoroids, and is coated on its outer surface to optimize its absorptance and emittance for regulation of temperature. The back sheet can be dimpled to minimize undesired thermal contact with the underlying spacecraft component and can be metallized on the surface facing the component to optimize its absorptance and emittance. The FCS systems can perform better than do MLI systems, at lower mass and lower cost and with greater volumetric efficiency

A comparison of communication tone and responding across users and developers in two R mailing lists

The R programming language has an active community of both users and developers, which maintain mailing lists to communicate. Given their differences in training and stability, the effects of communication tone on responding may differ across these two groups. We thus compared the prevalence and characteristics of different tones in the R-help user and Rdevel developer mailing lists over a ten-year period as well as their relation to replies. Our analyses indicate that developers displayed marginally more positive and negative tones than users. Moreover, developers seemed less influenced by tone when choosing to reply to messages. Overall, our results suggest that different tones may produce small differences in responding across users and developers

Paper 99: design guidelines versus practices for the Upper Seascheldt, the inland waterway connection between Antwerp and Ghent

Design guidelines for inland waterways are so far a national matter. PIANC InCom Working Group 141 "Design Guidelines for Inland Waterways" is nevertheless working on a report with a summary of existing guidelines and a methodology for the concept and detailed design of canals and rivers. For tidal rivers the design is a difficult process and an example is given through the accessibility of the Upper-Seascheldt for CEMT class IV and Va inland vessels between the port of Antwerp and the locks in Merelbeke. A combined evaluation based on concept design guidelines for canals, practices measured during a full-scale voyage and detailed design using ship handling simulators is discussed and illustrated

A Normalizing Computation Rule for Propositional Extensionality in Higher-Order Minimal Logic

The univalence axiom expresses the principle of extensionality for dependent type theory. However, if we simply add the univalence axiom to type theory, then we lose the property of canonicity - that every closed term computes to a canonical form. A computation becomes "stuck" when it reaches the point that it needs to evaluate a proof term that is an application of the univalence axiom. So we wish to find a way to compute with the univalence axiom. While this problem has been solved with the formulation of cubical type theory, where the computations are expressed using a nominal extension of lambda-calculus, it may be interesting to explore alternative solutions, which do not require such an extension. As a first step, we present here a system of propositional higher-order minimal logic (PHOML). There are three kinds of typing judgement in PHOML. There are terms which inhabit types, which are the simple types over Omega. There are proofs which inhabit propositions, which are the terms of type Omega. The canonical propositions are those constructed from false by implication. Thirdly, there are paths which inhabit equations M =_A N, where M and N are terms of type A. There are two ways to prove an equality: reflexivity, and propositional extensionality - logically equivalent propositions are equal. This system allows for some definitional equalities that are not present in cubical type theory, namely that transport along the trivial path is identity. We present a call-by-name reduction relation for this system, and prove that the system satisfies canonicity: every closed typable term head-reduces to a canonical form. This work has been formalised in Agda

Associations of neighborhood characteristics with active park use : an observational study in two cities in the USA and Belgium

Background: Public parks can be an important setting for physical activity promotion, but to increase park use and the activity levels of park users, the crucial attributes related to active park use need to be defined. Not only user characteristics and structural park attributes, but also characteristics of the surrounding neighborhood are important to examine. Furthermore, internationally comparable studies are needed, to find out if similar intervention strategies might be effective worldwide. The main aim of this study was to examine whether the overall number of park visitors and their activity levels depend on study site, neighborhood walkability and neighborhood income. Methods: Data were collected in 20 parks in Ghent, Belgium and San Diego, USA. Two trained observers systematically coded park characteristics using the Environmental Assessment of Public Recreation Spaces (EAPRS) tool, and park user characteristics using the System for Observing Play and recreation in Communities (SOPARC) tool. Multilevel multiple regression models were conducted in MLwiN 2.25. Results: In San Diego parks, activity levels of park visitors and number of vigorously active visitors were higher than in Ghent, while the number of visitors walking and the overall number of park visitors were lower. Neighborhood walkability was positively associated with the overall number of visitors, the number of visitors walking, number of sedentary visitors and mean activity levels of visitors. Neighborhood income was positively associated with the overall number of visitors, but negatively with the number of visitors being vigorously active. Conclusions: Neighborhood characteristics are important to explain park use. Neighborhood walkability-related attributes should be taken into account when promoting the use of existing parks or creating new parks. Because no strong differences were found between parks in high-and low-income neighborhoods, it seems that promoting park use might be a promising strategy to increase physical activity in low-income populations, known to be at higher risk for overweight and obesity

The Moderating Effect of Socioeconomic Status and Walkability on the Efficacy of Physical Activity Interventions

To enable physical activity (PA) interventions to better tailor procedures to participant characteristics, we investigated the role of neighborhood socioeconomic status (SES) and walkability on the differential effectiveness of adaptive versus static activity goals (AG vs. SG) and immediate versus delayed (IR vs. DR) reinforcement in a PA trial. Data was collected as a part of the WalkIT Arizona study, where healthy, inactive adults (n = 512) were instructed to wear an accelerometer daily for one year and were provided with daily goals for moderate-to-vigorous PA (MVPA). The intersection of goal types (adaptive and static) as well as reinforcement types (immediate and delayed) created four groups. Participants were block-randomized into one of four groups according to high/low neighborhood walkability and high/low neighborhood income. A linear regression model was fit to the data to predict mean daily MVPA based on the interaction of intervention condition and neighborhood walkability/income quadrant. Each neighborhood walkability/SES quadrant level and intervention group interaction was statistically significant. In high walkability/high SES and low walkability/high SES groups, daily MVPA was highest for the AG/IR intervention and lowest for the SG/DR intervention (β = 12.18, p \u3c .001; β = 9.11, p \u3c .001, respectively). In the low walkability/low SES group, MVPA was also lowest for the SG/DR intervention but was highest for the SG/IR intervention. (β= 9.12, p \u3c .001). Results were qualitatively different in the high walkability/low SES group, where the most MVPA was seen for the SG/DR intervention, while the least was observed for AG/DR (β = 5.66 , p \u3c .001). The results show that in a low-income/high-walkability environment, static goals and delayed reinforcement were most effective, which is the opposite of what was seen in other neighborhoods. These findings can be used to customize future physical activity interventions so that intervention strategies are most appropriate for participants’ demographic/environmental settings

The Rise of Community-Based Natural Resource Management Strategies as Explained by Transaction Costs

Community-based natural resource management (CBNRM) is favored over its predecessor, the fortress approach, for common pool resource (CPR) management. We strive to identify variables associated with successful CBNRM programs, and analyze whether their presence transaction costs can explain the shift in favored conservation strategy. By examining nine case studies of large mammals in Africa, we found that out of eight variables, moderate monitoring and adequate program incentives were the most critical various factors in determining CBNRM program outcomes. Furthermore, these variables, as well as others, contributed to a decrease in transaction costs

Bidirectional UWB Localization: A Review on an Elastic Positioning Scheme for GNSS-deprived Zones

A bidirectional Ultra-Wideband (UWB) localization scheme is one of the three widely deployed design integration processes ordinarily destined for time-based UWB positioning systems. The key property of the bidirectional UWB localization is its ability to serve both the navigation and tracking assignments on-demand within a single localization scheme. Conventionally, the perspective of navigation and tracking in wireless localization systems is viewed distinctly as an individual system because different methodologies were required for the implementation process. The ability to flexibly or elastically combine two unique positioning perspectives (i.e., navigation and tracking) within a single scheme is a paradigm shift in the way location-based services are observed. Thus, this article addresses and pinpoints the potential of a bidirectional UWB localization scheme. Regarding this, the complete system model of the bidirectional UWB localization scheme was comprehensively described based on modular processes in this article. The demonstrative evaluation results based on two system integration processes as well as a SWOT (strengths, weaknesses, opportunities, and threats) analysis of the scheme were also discussed. Moreover, we argued that the presented bidirectional scheme can also be used as a prospective topology for the realization of precise location estimation processes in 5G/6G wireless mobile networks, as well as Wi-Fi fine-time measurement-based positioning systems in this article.Comment: 30 pages, 12 figure