Space shuttle main engine: Interactive design challenges

The operating requirements established by NASA for the SSME were considerably more demanding than those for earlier rocket engines used in the military launch vehicles or Apollo program. The SSME, in order to achieve the high performance, low weight, long life, reusable objectives, embodied technical demands far in excess of its predecessor rocket engines. The requirements dictated the use of high combustion pressure and the staged combustion cycle which maximizes performance through total use of all propellants in the main combustion process. This approach presented a myriad of technical challenges for maximization of performance within attainable state of the art capabilities for operating pressures, operating temperatures and rotating machinery efficiencies. Controlling uniformity of the high pressure turbomachinery turbine temperature environment was a key challenge for thrust level and life capability demanding innovative engineering. New approaches in the design of the components were necessary to accommodate the multiple use, minimum maintenance objectives. Included were the use of line replaceable units to facilitate field maintenance automatic checkout and internal inspection capabilities

An Examination of Individual Behavioral Responses to the Fear of Crime

This research used data from the 2004 Omaha Conditions Survey to examine the relationship between the fear of crime and individual behavioral reactions to that fear. This research analyzed both protective and collective responses to the fear of crime. The analyses related both individual characteristics and neighborhood crime rates to protective and collective behavioral responses to the fear of crime. The research evaluated the effects of individual characteristics and neighborhood crime rates on reactions to the fear of crime using Hierarchical Linear Modeling (HLM). The fear of crime was found to have a statistically significant effect on individuals owning a dog for protection, owning a gun for protection, installing special locks, and keeping residence lights on at night. The fear of crime did not have a statistically significant effect on individuals participating in collective behaviors. The violent crime rate did have a statistically significant effect on the influence of the fear of crime on owning a gun, installing special locks, and installing a security system. For other behaviors tested, the violent crime rate had inconsistent effects on the influence of the fear of crime and on the intercepts of the equations. For the most part, the results supported the assertion that the reality of violent crime in an area elevates the intensity of the reactions to the fear of crime

Hemlock Woolly Adelgid (Hemiptera: Adelgidae) Management in Forest, Landscape, and Nursery Production

Hemlock woolly adelgid, Adelges tsugae (Annand) (Hemiptera: Adelgidae), has caused significant damage to both eastern [Tsuga canadensis (L.) Carrière] and Carolina hemlock (Tsuga caroliniana Englemann) (Pinales: Pinaceae) since it was first reported in the eastern United States. This adelgid is particularly damaging to these hemlock species due to a lack of co-evolved plant defenses and natural enemies able to suppress hemlock woolly adelgid populations. Management of hemlock woolly adelgid relies heavily on insecticides to prevent death of vulnerable trees. Biological control programs have released natural enemies of hemlock woolly adelgid to aid in control at the landscape level. Quarantine restrictions on hemlock are in place in some regions of the United States and Canada. These quarantines impact sales and shipment of hemlock trees from nurseries as well as other hemlock products. A review of insect biology, description of life stages, damage, management options, and quarantine restrictions for hemlock woolly adelgid is presented

Analytical Rescaling of Polymer Dynamics from Mesoscale Simulations

We present a theoretical approach to scale the artificially fast dynamics of simulated coarse-grained polymer liquids down to its realistic value. As coarse-graining affects entropy and dissipation, two factors enter the rescaling: inclusion of intramolecular vibrational degrees of freedom, and rescaling of the friction coefficient. Because our approach is analytical, it is general and transferable. Translational and rotational diffusion of unentangled and entangled polyethylene melts, predicted from mesoscale simulations of coarse-grained polymer melts using our rescaling procedure, are in quantitative agreement with united atom simulations and with experiments.Comment: 6 pages, 2 figures, 2 table

Detailed study of oxidation/wear mechanism in lox turbopump bearings

Wear of 440C angular contact ball bearings of the phase 2 high pressure oxygen turbopump (HPOTP) of the space shuttle main engine (SSME) has been studied by means of various advanced nondestructive techniques (NDT) and modeled with reference to all known material, design, and operation variables. Three modes dominating the wear scenario were found to be the adhesive/sheer peeling (ASP), oxidation, and abrasion. Bearing wear was modeled in terms of the three modes. Lacking a comprehensive theory of rolling contact wear to date, each mode is modeled after well-established theories of sliding wear, while sliding velocity and distance are related to microsliding in ball-to-ring contacts. Microsliding, stress, temperature, and other contact variables are evaluated with analytical software packages of SHABERTH(TM)/SINDA(TM) and ADORE(TM). Empirical constants for the models are derived from NIST experiments by applying the models to the NIST wear data. The bearing wear model so established precisely predicts quite well the average ball wear rate for the HPOTP bearings. The wear rate has been statistically determined for the entire population of flight and development bearings based on Rocketdyne records to date. Numerous illustrations are given

Behavior of Buff-Breasted Sandpipers (\u3ci\u3eTryngites subruficollis\u3c/i\u3e) during Migratory Stopover in Agricultural Fields

Background: Understanding the behavior of birds in agricultural habitats can be the first step in evaluating the conservation implications of birds’ use of landscapes shaped by modern agriculture. The existence and magnitude of risk from agricultural practices and the quality of resources agricultural lands provide will be determined largely by how birds use these habitats. Buff-breasted Sandpipers (Tryngites subruficollis) are a species of conservation concern. During spring migration large numbers of Buff-breasted Sandpipers stopover in row crop fields in the Rainwater Basin region of Nebraska. We used behavioral observations as a first step in evaluating how Buff-breasted Sandpipers use crop fields during migratory stopover. Methodology/Principal Findings: We measured behavior during migratory stopover using scan and focal individual sampling to determine how birds were using crop fields. Foraging was the most frequent behavior observed, but the intensity of foraging changed over the course of the day with a distinct mid-day low point. Relative to other migrating shorebirds, Buff-breasted Sandpipers spent a significant proportion of their time in social interactions including courtship displays. Conclusions/Significance: Our results show that the primary use of upland agricultural fields by migrating Buff-breasted Sandpipers is foraging while wetlands are used for maintenance and resting. The importance of foraging in row crop fields suggests that both the quality of food resources available in fields and the possible risks from dietary exposure to agricultural chemicals will be important to consider when developing conservation plans for Buff-breasted Sandpipers migrating through the Great Plains

Behavior of Buff-Breasted Sandpipers (\u3ci\u3eTryngites subruficollis\u3c/i\u3e) during Migratory Stopover in Agricultural Fields

Background: Understanding the behavior of birds in agricultural habitats can be the first step in evaluating the conservation implications of birds’ use of landscapes shaped by modern agriculture. The existence and magnitude of risk from agricultural practices and the quality of resources agricultural lands provide will be determined largely by how birds use these habitats. Buff-breasted Sandpipers (Tryngites subruficollis) are a species of conservation concern. During spring migration large numbers of Buff-breasted Sandpipers stopover in row crop fields in the Rainwater Basin region of Nebraska. We used behavioral observations as a first step in evaluating how Buff-breasted Sandpipers use crop fields during migratory stopover. Methodology/Principal Findings: We measured behavior during migratory stopover using scan and focal individual sampling to determine how birds were using crop fields. Foraging was the most frequent behavior observed, but the intensity of foraging changed over the course of the day with a distinct mid-day low point. Relative to other migrating shorebirds, Buff-breasted Sandpipers spent a significant proportion of their time in social interactions including courtship displays. Conclusions/Significance: Our results show that the primary use of upland agricultural fields by migrating Buff-breasted Sandpipers is foraging while wetlands are used for maintenance and resting. The importance of foraging in row crop fields suggests that both the quality of food resources available in fields and the possible risks from dietary exposure to agricultural chemicals will be important to consider when developing conservation plans for Buff-breasted Sandpipers migrating through the Great Plains

Treatment and Prevention of Opioid Use Disorder: Challenges and Opportunities

Treatment for opioid use disorder in the United States evolved in response to changing federal policy and advances in science. Inpatient care began in 1935 with the US Public Health Service Hospitals in Lexington, Kentucky, and Fort Worth, Texas. Outpatient clinics emerged in the 1960s to provide aftercare. Research advances led to opioid agonist and opioid antagonist therapies. When patients complete opioid withdrawal, return to use is often rapid and frequently deadly. US and international authorities recommend opioid agonist therapy (i.e., methadone or buprenorphine). Opioid antagonist therapy (i.e., extended-release naltrexone) may also inhibit return to use. Prevention efforts emphasize public and prescriber education, use of prescription drug monitoring programs, and safe medication disposal options. Overdose education and naloxone distribution promote access to rescue medication and reduce opioid overdose fatalities. Opioid use disorder prevention and treatment must embrace evidence-based care and integrate with physical and mental health care

Killdeer \u3ci\u3eCharadrius vociferus\u3c/i\u3e breeding abundance and habitat use in the Eastern Rainwater Basin, Nebraska

The Killdeer Charadrius vociferous is a common shorebird that breeds throughout much of North America. The most recent estimate of the total population of Killdeer is 1 million individuals, but this estimate is supported by few quantitative studies. We used distance sampling to survey Killdeer in the agricultural ecosystem of the Eastern Rainwater Basin, Nebraska. Our results show that as many as 100,000 Killdeer may breed in the Eastern Rainwater Basin. The region we surveyed covers a very small portion of the Killdeer’s overall breeding range, suggesting that the Killdeer population is likely \u3e1 million birds. We also evaluated habitat use in the heavily modified Eastern Rainwater Basin. Our results show that Killdeer primarily occupy row crop agricultural fields and prefer fields planted to soybeans the previous growing season over those that had been planted to corn in the previous season. Our results highlight the need to further assess Killdeer population size and trends throughout the species’ range, and also evaluate localized and range-wide threats to the species’ long-term survival while the species is common