An experimental investigation of the hypergolic ignition of some polymeric fuels with oxygen

Hypergolic ignition of polymeric fuels with oxyge

Allocating Sampling Effort to Equalize Precision of Electrofishing Catch per Unit Effort

We used a spatially explicit simulation model to examine the effects of lake shoreline length and lakewide fish density on electrofishing catch-per-unit-effort (CPUE) estimates of fish density. We also tested model predictions regarding the influence of shoreline length and fish density on precision of CPUE estimates by analyzing electrofishing data from Ohio reservoirs for juvenile gizzard shad Dorosoma cepedianum, which is a schooling fish, and largemouth bass Micropterus salmoides, a more solitary fish. Our goals were to estimate the impact of these factors on variability associated with population estimates derived from CPUE and to determine how these factors influence the minimum number of transects required to sample populations with a reliable degree of precision. Neither ‘‘minimum transect number’’ (number of transects sampled per lake in which all of 10 replicate simulations provided density estimates within 610% of the mean) nor ‘‘minimum variance’’ (variance among estimates given 20 transects/estimate) were affected by the size of lake being sampled. However, minimum transect number decreased with lakewide fish density, and minimum variance increased with fish density, particularly when fish were patchily distributed. Our results show that it is reasonable to choose one effort level (i.e., a constant number of transects per lake) for a variety of systems. This constant level of effort can achieve acceptable precision in systems differing in lake shoreline length, fish density, and fish patchiness, except in those systems having extremely low overall fish densities. In this case, more transects may be required.Support for this project was provided by Federal Aid in Sport Fish Restoration, project F-69-P, administered jointly by the U.S. Fish and Wildlife Service and the Ohio Division of Wildlife, and by the Department of Zoology, Ohio State University

Regulating Micromobility: Examining Transportation Equity and Access

This paper evaluates the various ways cities have or are attempting to address e-scooter usage equity concerns, with a focus on Atlanta, Georgia as compared to Austin, Texas; Charlotte, North Carolina; Los Angeles, California; and Portland, Oregon. The cities were evaluated by the laws in effect at the time of coding, which occurred during the project period of October through December 2019. To explore how existing laws and regulations affect access to e-scooters, this research was guided by the following overarching questions: How equitable is access to e-scooters? How can equitable access to e-scooters be improved? How can a data-driven approach be used to craft inclusive and effective micromobility regulations for Atlanta, Georgia, and other cities nationwide

Regulating Micromobility: Examining Transportation Equity and Access

This paper evaluates the various ways cities have or are attempting to address e-scooter usage equity concerns, with a focus on Atlanta, Georgia as compared to Austin, Texas; Charlotte, North Carolina; Los Angeles, California; and Portland, Oregon. The cities were evaluated by the laws in effect at the time of coding, which occurred during the project period of October through December 2019. To explore how existing laws and regulations affect access to e-scooters, this research was guided by the following overarching questions: How equitable is access to e-scooters? How can equitable access to e-scooters be improved? How can a data-driven approach be used to craft inclusive and effective micromobility regulations for Atlanta, Georgia and other cities nationwide

Life After Death in Lake Erie: Nutrient Controls Drive Fish Species Richness, Rehabilitation

We explored the recent (1969–1996) dynamics of fish communities within Lake Erie, a system formerly degraded by eutrophication and now undergoing oligotrophication owing to phosphorus abatement programs. By merging bottom trawl data from two lake basins of contrasting productivity with life-history information (i.e., tolerances to environmental degradation, diet and temperature preferences), we examined (1) the relationship between system productivity and species richness, (2) whether fish communities are resilient to eutrophication, and (3) whether oligotrophication necessarily leads to reduced sport and commercial fish production. Reduced phosphorus loading has led to fish community rehabilitation. In the productive west basin, six species tolerant of eutrophy (i.e., anoxia, turbidity) declined in abundance, whereas the abundance of three intolerant species increased through time. In the less productive central basin, although only one tolerant species declined, four species intolerant of eutrophic conditions recovered with oligotrophication. These differential responses appear to derive from dissimilar mechanisms by which reduced productivity alters habitat and resource availability for fishes. Specifically, enhanced bottom oxygen, combined with reduced biogenic turbidity and sedimentation, likely drove the loss of tolerant species in the west basin by reducing detrital mass or the ability of these species to compete with intolerant species under conditions of improved water clarity. In contrast, reduced bottom anoxia, which enhanced availability of cool- and cold-water habitat and benthic macroinvertebrate communities, appears important to the recovery of intolerant species in the central basin. Ultimately, these productivity-induced shifts caused species richness to decline in Lake Erie’s west basin and to increase in its central basin. Beyond confirming that unimodal models of productivity and species diversity can describe fish community change in a recovering system, our results provide optimism in an otherwise dismal state of affairs in fisheries management (e.g., overexploitation), given that many recovering intolerant species are desired sport or commercial fishes.Support for this work was provided by (1) Federal Aid in Sport Fish Restoration F-69-P (to R. A. Stein), administered jointly by the U.S. Fish and Wildlife Service and ODNR-ODW, (2) the Department of Evolution, Ecology, and Organismal Biology at The Ohio State University, and (3) a Presidential Fellowship awarded to S. A. Ludsin by The Ohio State University

Markov chain estimation of avian seasonal fecundity

Avian seasonal fecundity is of interest from evolutionary, ecological, and conservation perspectives. However, direct estimation of seasonal fecundity is difficult, especially with multi-brooded birds, and models representing the renesting and quitting processes are usually required. To explore the consequences of modeling decisions on inference about avian seasonal fecundity, we generalize previous Markov chain (MC) models of avian nest success to formulate two different MC models of avian seasonal fecundity that represent two different ways to model renesting decisions and breeding cessation. We parameterize both Markov chains (regular and absorbing) for two species (Eastern Meadowlark, Sturnella magna, and Dickcissel, Spiza americana) and compare the results using mean-square error of the estimated number of successful broods per breeding female. We also provide formulae for estimating the expected variation in female breeding success. The absorbing MC performed better for both species, although the regular MC performed almost as well when the duration of the breeding season was estimated by taking the 95th percentile of a negative binomial distribution fit to the observed durations among all females. In their simplest form the models contain very few parameters (four or five) and should also prove useful as a foundation for more complex models of avian seasonal fecundity and demography

Modeling sources of variation for growth and predatory demand of Lake Erie walleye (Stizostedion vitreum), 1986-1995

Abstract in English and FrenchGiven the variable nature of the Lake Erie ecosystem, we investigated biotic and abiotic sources of variation for walleye (Stizostedion vitreum) growth, consumption, and population-wide predatory demand. We determined how temperature, population structure, and age-specific consumption influenced walleye growth and consumption during 1986-1995. For each year, we used individual-based bioenergetics modeling to compare growth and consumption by walleye in Lake Erie's western or central basin with those of walleye moving seasonally between basins. Population structure strongly affected walleye growth and consumption but had little influence on interbasin growth rate comparisons. Based on water temperature alone, growth and consumption by western basin walleye were generally lower than for central basin or migratory populations and were more limited by summer water temperatures. In simulations combining effects of population structure, temperature, and age-specific consumption, migratory walleye grew most rapidly, taking advantage of temperature-related growth peaks in both basins. Estimates of walleye predatory demand declined with population size from 1988 through 1995. With natural feedbacks, predatory demand interacts with prey production, limiting walleye reproductive potential when prey availability is low. However, immediate impact on predatory inertia is limited, complicating our ability to predict how predatory demand and prey availability interact in Lake Erie.Support for this project was provided by a University Fellowship from the Graduate School of the Ohio State University (to M.W.K.) and by Federal Aid in Sportfish Restoration F-69-P, administered jointly by the U.S. Fish and Wildlife Service and the Ohio Division of Wildlife, and by the Department of Zoology, Ohio State University

Generalized Interpolation Material Point Approach to High Melting Explosive with Cavities Under Shock

Criterion for contacting is critically important for the Generalized Interpolation Material Point(GIMP) method. We present an improved criterion by adding a switching function. With the method dynamical response of high melting explosive(HMX) with cavities under shock is investigated. The physical model used in the present work is an elastic-to-plastic and thermal-dynamical model with Mie-Gr\"uneissen equation of state. We mainly concern the influence of various parameters, including the impacting velocity $v$, cavity size $R$, etc, to the dynamical and thermodynamical behaviors of the material. For the colliding of two bodies with a cavity in each, a secondary impacting is observed. Correspondingly, the separation distance $D$ of the two bodies has a maximum value $D_{\max}$ in between the initial and second impacts. When the initial impacting velocity $v$ is not large enough, the cavity collapses in a nearly symmetric fashion, the maximum separation distance $D_{\max}$ increases with $v$. When the initial shock wave is strong enough to collapse the cavity asymmetrically along the shock direction, the variation of $D_{\max}$ with $v$ does not show monotonic behavior. Our numerical results show clear indication that the existence of cavities in explosive helps the creation of ``hot spots''.Comment: Figs.2,4,7,11 in JPG format; Accepted for publication in J. Phys. D: Applied Physic