Effect of reduced aft diameter and increased blade number on high-speed counterrotation propeller performance

Performance data of 0.17-scale model counterrotation pusher propeller configurations were taken in the NASA Lewis 8- by 6-Foot Supersonic Wind Tunnel at Mach numbers of 0.66, 0.71, 0.75, and 0.79. These tests investigated the aerodynamic performance of the unducted fan (UDF) demonstrator propeller engine developed in a joint program by General Electric and NASA. Data were recorded to show the effect on counterrotation propeller cruise efficiency of two takeoff noise-reduction concepts. These two concepts are reduced aft blade diameter and increased forward blade number. The four configurations tested were a baseline (F1/A1 8/8) configuration, a reduced aft diameter (F1/A3 8/8) configuration, an increase forward blade number (F1/A1 9/8) configuration, and a combination of the latter two (F1/A3 9/8) configurations. Data were collected with a complex counterrotation propeller test rig via rotating thrust and torque balances and pressure instrumentation. Data comparisons documented the power differences between the baseline and the reduced aft diameter concepts. Performance comparisons to the baseline configuration showed that reducing the aft blade diameter reduced the net efficiency, and adding a blade to the front rotor increased the net efficiency. The combination of the two concepts showed only slightly lower net efficiency than the baseline configuration. It was also found that the counterrotation demonstrator propeller model (F7/A7 8/8) configuration outperformed the baseline (F1/A1 8/8) configuration

An Empirical Exploration of Exchange Rate Target-Zones

In the context of a flexible-price monetary exchange rate model and the assumption of uncovered interest parity, we obtain a measure of the fundamental determinant of exchange rates. Daily data for the European Monetary System are used to explore the importance of non-linearities in the relationship between the exchange rates and fundamentals. Many implications of existing "target-zone" exchange rate models are tested; little support is found for existing non-linear models of limited exchange rate flexibility.

Testing in Translation: Conducting Usability Studies With Transnational Users

What do we mean by usability in everyday life? For us, everyday life implies the series of choices and decisions that happen each day as people are trying to get things done. These things are often taken for granted, they might seem mundane, they may be overlooked. Usability inhabits everyday life in the documents used by a Vietnamese mother of two young children, having recently moved to the United States, and navigating the healthcare system in a new country for the first time. Usability shows up again as a Chinese couple considers whether or not to move out of their father’s home in a Seattle neighborhood, but wonder how it might impact the family’s ability to afford health insurance

MODELING ALTERNATIVE POLICIES FOR GHG MITIGATION FROM FORESTRY AND AGRICULTURE

A key consideration for development of energy and climate policy affecting the forestry and agricultural sectors is that the selection of specific mechanisms implemented to achieve bioenergy production and/or greenhouse gas (GHG) mitigation targets may have substantial effects on landowner incentives to adopt alternative practices. For instance, the prices of allowances and offsets are expected to diverge under some policies being considered where there is a binding cap on the quantity of offsets from the agricultural and forest sectors. In addition, provisions that limit or exclude specific practices from receiving carbon payments will affect the quantity and cost of GHG mitigation opportunities available. In this study, the recently updated Forest and Agriculture Sector Optimization Model with GHGs (FASOMGHG) was used to estimate GHG mitigation potential for private land in the contiguous U.S. under a variety of GHG price policies. Model scenarios suggest that U.S. forestry and agriculture could provide mitigation of 200 – 1000 megatons carbon dioxide equivalent per year (Mt CO2e/year) at carbon prices of $15 to$50/tCO2e. Binding limits on offsets have increasingly large effects on both the total magnitude and distribution of GHG mitigation across options over time. In addition, discounting or excluding payments for forest sinks can reduce annualized land-based mitigation potential 37-90 percent relative to the full eligibility scenario whereas discounting or excluding agricultural practices reduces mitigation potential by less than 10 percent.Climate policy, energy policy, FASOMGHG, GHG mitigation, Agricultural and Food Policy, Environmental Economics and Policy, Resource /Energy Economics and Policy, C61, Q42, Q54,

Comparative Life Histories of Georgia and Virginia Cotton Rats

Adult hispid cotton rats (Sigmodon hispidus) were collected from the field monthly for \u3e2 years from populations near the northern edge of their range in Virginia and contemporaneously from south-central Georgia. Body measurements and weights were taken at capture, and after dissection embryos, corpora lutea, and placental scars were counted and measured; testes and seminal vesicles were dissected out, measured, and weighed. This allowed comparison of several life-history parameters between the populations and tests of several life-history hypotheses. The breeding season was up to 2 months longer in Georgia than in Virginia, where there was typically a 3-month or longer winter inactive period. Some reproductive activity was observed among Georgia females in all 12 calendar months, whereas pregnancies were never observed in Virginia during November– February. Average litter sizes were significantly higher in Virginia (5.91 ± 6 1.41, up to 13) than in Georgia (5.16 ± 6 1.79, up to 9); this difference may partly result from a higher incidence of embryo resorption and prenatal mortality in the Georgia population, primarily in the cooler 6 months of the year. Virginia rats averaged significantly smaller for both sexes, but this was likely the result of a younger age distribution. Among reproductive males and females, no body-size differences were found between populations except that pregnant females from Virginia averaged significantly longer. Fifty percent and 75% of the random sample of adult females and males, respectively, were reproductively active in Georgia, whereas only 35% and 40% were reproductively active in Virginia. Spermatogenically active males in Virginia had significantly greater relative gonadal mass than their Georgia counterparts. Overwinter survival of parous females was lower in Virginia. Virginia populations, in a more seasonal environment, displayed a more r-selected life history, with greater reproductive allocation, faster growth (except over winter), higher mortality, and less iteroparity

Predicting Personalized Responses to Dietary Fiber Interventions: Opportunities for Modulation of the Gut Microbiome to Improve Health

Inadequate dietary fiber consumption has become common across industrialized nations, accompanied by changes in gut microbial composition and a dramatic increase in chronic metabolic diseases.The human gut microbiome harbors genes that are required for the digestion of fiber, resulting in the production of end products that mediate gastrointestinal and systemic benefits to the host. Thus, the use of fiber interventions has attracted increasing interest as a strategy to modulate the gut microbiome and improve human health. However, considerable interindividual differences in gut microbial composition have resulted in variable responses toward fiber interventions. This variability has led to observed nonresponder individuals and highlights the need for personalized approaches to effectively redirect the gut ecosystem. In this review, we summarize strategies used to address the responder and nonresponder phenomenon in dietary fiber interventions and propose a targeted approach to identify predictive features based on knowledge of fiber metabolism and machine learning approaches

Effects of Human Disturbances on the Behavior of Wintering Ducks

Human activity causes wintering waterfowl to expend energy to avoid humans at a time in their annual cycle when energy conservation is important to survival, migration, and breeding reserves. Understanding the effects of recreational activities on waterfowl is important to managing natural resource areas where migratory birds depend on wetland habitat for resting and feeding. We investigated responses of 7 species of dabbling ducks to 5 different experimental human activities, (a pedestrian, a bicyclist, a truck traveling at 2 different speeds, and an electric passenger tram). Responses of ducks depended on type of disturbance, species, and distance from disturbances. Most birds responded to the treatments. People walking and biking disturbed ducks more than vehicles did. Northern pintail (Anas acuta) was the species least sensitive to disturbance, whereas American wigeon (A. americana), green-winged teal (A. crecca), and gadwall (A. strepera) were most sensitive. Ducks were more likely to fly when closer to sources of disturbance. These results will be helpful to managers making decisions about public use that strive to minimize disturbance of dabbling ducks

Expert Yet Vulnerable: Understanding the Needs of Transit Dependent Riders to Inform Policy and Design

Transportation is a crucial resource that links people to jobs, social networks, community and services. The transit dependent -- those who do not own private vehicles -- occupy a unique position. They are expert in their knowledge of public transportation while vulnerable to the failures and limitations of transit. This paper presents the results of a study that is aimed at understanding the lived experience of transit dependent riders. Using a framework of structuration theory as an analytic lens, we provide a thematic analysis of qualitative data including interviews with socially connected groups of people and video diaries. The results demonstrate the expertise that transit dependent riders have about transit and its policies and how they deploy that expertise in productive and cunning ways to make the system work for them. The analysis of this data resulted in three categories of agency to consider when designing for vulnerable populations: resourcefulness, reciprocity and powerlessness. The paper concludes by advocating for a human-centered approach to designing systems in community informatics and offers a set of guiding questions for designers of information and communication technologies (ICTs) to consider, especially with regards to vulnerable populations