Transient Effects on Dynamic Torque for Butterfly Valves

Butterfly valves are versatile components widely used in hydraulic systems as shutoff and throttling valves. Butterfly valve components must be able to withstand the forces and torques that are generated with use. Dynamic torque data are usually obtained in a test lab for a variety of steady state flow conditions; however the dynamic torque under transient (unsteady flow) conditions may be significantly different than that found in the laboratory. If a valve is closed too fast, especially in long systems, large transient pressures are generated and travel as waves through the pipeline. These transient waves increase the pressure difference across the valve, which in turn increases the dynamic torque that is applied to the valve. The effects of the increased dynamic torque are more significant in larger butterfly valves since dynamic torque is a function of the diameter raised to the third power. If the increased dynamic torque is larger than the torque that the valve was built to withstand, valve or actuator failure could result. The objective of this research was to examine the effect of transients on dynamic torque in a 48-inch diameter butterfly valve operation as a function of pipe length and valve closure time (starting at full open) and compare the results to traditional steady state dynamic torque data. It was found that longer pipeline lengths along with smaller valve closure times created the largest percent difference in transient dynamic torque from the steady state dynamic torque. This difference was as high as 711% in a 20,000-foot long pipeline when the valve was closed in 36 seconds. Transient effects should be considered in the design and manufacturing of butterfly valves as well as during the operation of the valve once it is installed

Sexual Selection On Body Size, Territory And Plumage Variables In A Population Of Darwin’S Finches

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/137434/1/evo00291.pd

Rewiring the Niche: Sympathetic Neuropathy Drives Malignant Niche Transformation

In recent years, it has become increasingly evident that hematological malignancies can alter their microenvironment, but the therapeutic implications of these changes and potential targets have not been well characterized. Recent findings now describe how sympathetic neuropathy can drive malignant transformation of the hematopoietic stem cell niche in hematopoietic malignancies

Confronting Challenges at the Intersection of Rurality, Place, and Teacher Preparation: Improving Efforts in Teacher Education to Staff Rural Schools

Recruiting and retaining highly qualified teachers in rural schools is a persistent struggle in many countries, including the U.S. Salient challenges related to poverty, geographic isolation, low teacher salaries, and a lack of community amenities seem to trump perks of living in rural communities. Recognizing this issue as a complex and hard to solve fixture in the composition of rural communities, we sought to understand how teacher preparation programs might better prepare preservice teachers for successful student teaching placements and, ideally, eventual careers in rural schools. In this study, we explore teacher candidatesΓÇÖ perceptions of rurality while examining how specific theory, pedagogy, and practice influence their feelings of preparedness for working in a rural school. Using pre- and post- questionnaire data, classroom observations, and reflections, we assess the effectiveness of deliberate efforts in our teacher preparation program to increase readiness for rural teaching. In our analysis and discussion, we draw on critical and sociocultural theories to understand the experiences of a cohort of teacher candidates as they explore personal histories, the importance of place, expectations, and teaching strategies for rural contexts. While rural education researchers have long lamented the struggle to recruit and retain teachers, there is relatively little known about intentional efforts to prepare teachers specifically for rural classrooms. We conclude our article with recommendations for enhancing teacher preparation programs in ways that might result in significant progress toward the goal of staffing rural schools with the highly skilled teachers all students deserve

The New Deal, Race, and Home Ownership in the 1920s and 1930s

Many federal government housing policies began during the New Deal of the 1930s. Many claim that minorities benefited less from these policies than whites. We estimate the relationships between policies in the 1920s and 1930s and black and white home ownership in farm and nonfarm settings using a pseudo-panel of repeated cross-sections of households in 1920, 1930, and 1940 matched with policy measures in 460 state economic areas. The policies examined include FHA mortgage insurance, HOLC loan refinancing, state mortgage moratoria, farm loan programs, public housing, public works and relief, and payments to farmers to take land out of production.

Plant species richness across the Himalaya driven by evolutionary history and current climate

The Himalaya, the world's largest mountain chain, spans a wide variety of climates. Further, different locations have historically experienced climatic perturbations to different degrees. This makes it the ideal region to assess roles of contemporary climate, diversification (speciation minus extinction), and dispersal barriers in affecting local species richness. Based on a review of all available Himalayan floras, we determined that 8765 native angiosperm species are presently documented and recorded their location and elevational distributions. We compared species richness and measures of phylogenetic structure in 100-m elevational bands for all species combined and for three major life-forms separately (trees, shrubs, and herbs) across the Himalaya. Species richness declines threefold from the east to the northwest of the Himalaya. Along elevational gradients, tree richness monotonically declines in the northwest, but peaks at ~1000 m in the east. Shrubs and herbs peak in richness at mid-elevations (~2000 m). Mean temperature and annual precipitation together explain ~60% of the variation in species richness. The general phylogenetic pattern observed in this study is that phylogenetic clustering (i.e., more closely related species on fewer long branches) increases from low to high elevations, but with a dip at mid-elevations (2000–3000 m), which may result from a mixing of distinct floras, but is not associated with exceptionally high richness. High clustering at higher elevations (3000–4500 m) and in the drier northwest suggests ongoing diversification dynamics limit richness in these harsher environments. The effects of diversification dynamics appear to be smaller than those of contemporary climate in limiting buildup of species numbers

Constructing a database of alien plants in the Himalaya to test patterns structuring diversity

Differences in the number of alien plant species in different locations may reflect climatic and other controls that similarly affect native species and/or propagule pressure accompanied with delayed spread from the point of introduction. We set out to examine these alternatives for Himalayan plants, in a phylogenetic framework. We build a database of alien plant distributions for the Himalaya. Focusing on the well-documented regions of Jammu & Kashmir (west) and Bhutan (east) we compare alien and native species for (1) richness patterns, (2) degree of phylogenetic clustering, (3) the extent to which species-poor regions are subsets of species-rich regions and (4) continental and climatic affinities/source. We document 1470 alien species (at least 600 naturalised), which comprise ~14% of the vascular plants known from the Himalaya. Alien plant species with tropical affinities decline in richness with elevation and species at high elevations form a subset of those at lower elevations, supporting location of introduction as an important driver of alien plant richness patterns. Separately, elevations which are especially rich in native plant species are also rich in alien plant species, suggesting an important role for climate (high productivity) in determining both native and alien richness. We find no support for the proposition that variance in human disturbance or numbers of native species correlate with alien distributions. Results imply an ongoing expansion of alien species from low elevation sources, some of which are highly invasive

A model for collaboration networks giving rise to a power law distribution with exponential cutoff

Recently several authors have proposed stochastic evolutionary models for the growth of complex networks that give rise to power-law distributions. These models are based on the notion of preferential attachment leading to the ``rich get richer'' phenomenon. Despite the generality of the proposed stochastic models, there are still some unexplained phenomena, which may arise due to the limited size of networks such as protein, e-mail, actor and collaboration networks. Such networks may in fact exhibit an exponential cutoff in the power-law scaling, although this cutoff may only be observable in the tail of the distribution for extremely large networks. We propose a modification of the basic stochastic evolutionary model, so that after a node is chosen preferentially, say according to the number of its inlinks, there is a small probability that this node will become inactive. We show that as a result of this modification, by viewing the stochastic process in terms of an urn transfer model, we obtain a power-law distribution with an exponential cutoff. Unlike many other models, the current model can capture instances where the exponent of the distribution is less than or equal to two. As a proof of concept, we demonstrate the consistency of our model empirically by analysing the Mathematical Research collaboration network, the distribution of which is known to follow a power law with an exponential cutoff

Targeted Employee Retention: Performance-Based and Job-Related Differences in Reported Reasons for Staying

A content model of 12 retention factors is developed in the context of previous theory and research. Coding of open-ended responses from 24,829 employees in the leisure and hospitality industry lends support to the identified framework and reveals that job satisfaction, extrinsic rewards, constituent attachments, organizational commitment, and organizational prestige were the most frequently mentioned reasons for staying. Advancement opportunities and organizational prestige were more common reasons for staying among high performers and non-hourly workers, and extrinsic rewards was more common among low performers and hourly employees, providing support for ease/desirability of movement and psychological contract rationales. The findings highlight the importance of differentiating human resource management practices when the goal is to retain those employees valued most by the organization