New functional redundancy approaches for attitude control thruster systems

Functional redundancy safeguards for inert gas attitude control thruster system

A discriminant approach to parameter estimation in the linear model with unknown variance-covariance matrix

There are no author-identified significant results in this report

Hydrogeologic Framework And Water Balance Investigation of Land near the Gothenburg Canal System

The Nebraska Public Power District (NPPD) requested that Conservation and Survey Division (CSD) develop a local hydrogeologic framework and conceptual water budget for a parcel of land near a segment of canal in the Gothenburg Canal System to determine likely sources of ponded surface water that are ephemerally present on the parcel. The study seeks to assess the parcel scale water budget and to better understand the parcel-scale hydrology and hydrogeology. The object of this project is to provide reliable information to NPPD and its customers along a small portion of the canal. Information from this report may influence, or be incorporated into, NPPD’s canal water accounting and operations tools. This publication also describes sources, methods, limitations, and recommendations for future work to improve rigor and/or limit uncertainties

Hallum Architects, Inc., Marketing Brochure

Six-page color brochure describing architectural services for churches offered by Hallum Architects, Ins. Illustrated with photographs of church buildings

Church Architecture: A History of Influences

A sixteen-page document by V. Aubrey Hallum describing the historical and doctrinal contexts for designing buildings for Churches of Christ

Investigation of the Effects of Oxidizer Temperature on the Stability of a Gas-Centered Swirl Coaxial Injector

Rocket engines achieve extraordinary high energy densities within the chamber in the form of high pressure turbulent combustion. Successful design of these engines requires sustained, stable operation of a combustor exposed to extreme thermal loads. Slight deviations in operating conditions can then incur consequences ranging from reduced performance up to catastrophic failure in the face of excess heat loading. Sustained periodic oscillations, termed combustion instabilities, are often encountered during development, as fluctuations produced by combustion noise couple with heat release modes by way of modulation of the feed system, injector hydrodynamics, chemical kinetics, and mixing and atomization process. Successful development of reliable, high performance rocket engines can be achieved either through a thorough understanding of both injector and combustor dynamics to mitigate these instabilities or through the laborious design/test iteration process. This document describes a two-fold work by the author. The first objective considers the acquisition of high-fidelity data sets of a single gas-centered swirl coaxial injector for use in the validation of computational models. Secondly, the stability of this injector was studied at two oxidizer inlet temperatures. Combustion stability was assessed through variation of the combustor geometry. Previous research shows that varying this geometry can either drive or dampen pressure oscillations. Testing was conducted on an experimental test bed equipped with modular sections to accommodate changing oxidizer post and chamber lengths. A single gas-centered swirl coaxial injector was used, with operating parameters based on the RD-180 injector element, such as equivalence and momentum flux ratios. Two oxidizer inlet temperatures were chosen. The first was oxygen combusted with gaseous hydrogen at lean conditions in a preburner to produce hot oxidizer near 700 K. The second was pure oxygen delivered at room temperature. Results from the test campaign revealed the system to be classically stable across all configurations and inlet conditions tested, with pressure perturbations less than 10% of the mean chamber pressure. Discriminating behavior was observed between the two oxidizer inlet temperatures. At elevated temperatures, peak-to-peak pressure oscillations observed throughout the system were small at less than 4% of the mean chamber pressure. There was no observed dependency of the amplitude on geometry. At ambient temperatures, the pressure oscillations ranged from 4% up to 7%. The increase in amplitudes were similar to that of the acoustic refection coefficient between the oxidizer and chamber gas, based on their acoustic specific impedance. An increase in the acoustic transmission coefficient was also observed, going from hot to ambient oxidizer. The increase in these two values would not necessarily lead to enhanced coupling between the chamber and resonance behavior in the post, but is expected to amplify pressure oscillations. At the ambient condition, clear variation in amplitudes were generated through manipulation of the geometry. The general trend matched previous experiments but was not followed by all tested configurations. It was determined that a methodology solely based on the effective resonator wavelength was not sufficient to predict the amplitude of pressure oscillations. Instead, a better predictor of amplitude was found based on the alignment of the system with postulated vortex generation from the injector face and impingement on the chamber walls. The time between local pressure oscillations and final impingement of the resulting vortices fell between one and two cycles of the fundamental longitudinal chamber mode, increasing linearly in strength as phase lag increased

Informing water use decision-making for waterfowl and agricultural production on a ranch along the North Platte River, Nebraska

In 2014, operators of a ranch along the North Platte River approached Conservation and Survey Division seeking expertise to interpret data collected on their ranch. The interpretations inform ranch decisions to accomplish operators’ goals. This publication documents the work by: 1) characterizing the ranch, 2) summarizing data collected, 3) characterizing hydrogeology of the site and the adjacent reach, and 4) conceptualizing groundwater/surface water interaction. The ranch is a recreation property and a migratory waterfowl refuge with a few general goals: 1) develop and maintain high-quality wet meadow habitat, 2) maximize the extent and duration of surface water on the property in existing wet meadows, sloughs, and ponds, and 3) maintain a level of agricultural production that can be used to mitigate costs. An adaptive program of data collection and synthesis was developed and implemented from 2014 to 2019. It is ongoing. Groundwater data collection began in 2014. Weather and stream data collection began in 2015. Weather data was served to the internet in 2016. Radio telemetry was added to groundwater and stream data in 2017 and discontinued in 2018. Summaries of collected synthesized data began quarterly and currently occur monthly. The observation network at the ranch currently generates about 15,000 records a month at seven locations. Hydraulic relationships at the ranch are more complex than initially conceptualized. Water table configuration indicates flow in unexpected directions, groundwater response sometimes precedes surface water response to precipitation, and stress responses can vary seasonally. Stream/groundwater response to precipitation is distinctly non-linear. The vadose zone is generally thin, yet may have significant influence on observations. The ranch has successfully developed diverse habitat features on the site including wet meadows, ephemeral stream channels, sloughs, grassy and woody hummocks, and ponded areas. These areas are populated by varieties of ducks, geese and herons, as well as many other riparian, woodland, and grassland species, including beneficial invertebrates. Culverts have been installed along many of the channels and sloughs such that the water level in upstream segments can be managed to change the stream or slough stage in reaches where water is flowing. The groundwater/surface water storage dynamic can therefore be managed to maximize habitat and wildlife benefits as well as groundwater storage and return flow. Much work remains

Results of Test-Hole Drilling for Observation Well Planning in the Upper Loup Natural Resources District, Fall 2016

The High Plains Aquifer underlies much of Nebraska (Figure 1). It is the primary source of groundwater within the Upper Loup Natural Resources District (ULNRD) of central Nebraska (Figure 2). Water derived from the aquifer is an important natural resource for the area and supplies water for recreation, wildlife and agriculture, as well as domestic, municipal, and industrial uses. A general lack of water level observations in the region (Figure 3), recently developed groundwater irrigated acres along the upper Calamus River (Figure 4), falling spring water levels measured in existing irrigation wells (Figure 5), and a stable to falling stream gage since 2010 on the Calamus River near Harrup (Figure 6) have raised concerns about possible changes in water availability, groundwater-surface water relationships and water quality in the area, prompting the ULNRD to propose collection of baseline data in the region. The Conservation and Survey Division (CSD) was enlisted by the ULNRD to conduct a test-hole drilling study of the area. The purpose of this study was to obtain hydrogeological data that would assist the ULNRD with the planning, placement, and design of observation wells in southern Brown and eastern Blaine Counties. Four priority areas were selected to increase the spatial density of CSD test holes and NRD monitoring wells to better identify conditions along the Calamus and North Loup Rivers. Three test holes were drilled between September 27 and October 13, 2016. Hydrogeological data collected from the test holes supplied information from which observation well specifications were derived. As a result, observation wells were constructed in October 2016. . Additionally, this study provided training to ULNRD staff on procedures for test-hole drilling and the design and placement of future observation wells

Petroleum Pipelines—Facts and Safety

Since 2005, increased United States oil and natural gas production and increased oil output from Canadian oil sands has outpaced existing transportation infrastructure. As a result, there are plans to increase both natural gas and oil pipelines in the U.S. Although increased production of hydrocarbons has economic benefit, there are concerns about leaks and spills from petroleum pipelines and their potential environmental impacts. There has been particular concern about protecting Nebraska’s water resources from possible leaks of the proposed Keystone XL pipeline extension, the permit application for which was denied by the U.S. Department of State on November 6, 2015. TransCanada responded to this action by initiating an international arbitration case in January 2016, under the North American Free Trade Agreement. Regardless of one’s viewpoint of the Keystone XL project proposal, petroleum pipelines are an undeniably important part of our transportation infrastructure. They provide heat for homes, fuel for transportation, and chemicals used to produce products ranging from fertilizer to plastics. According to the Nebraska Pipeline Association, there are more than 25 million miles (40 million kilometers) of petroleum pipelines in the United States, and these pipelines are operated by more than 3,000 companies. Nebraska Pipeline Association member companies alone operate more than 102,000 miles (164,000 kilometers) of transmission pipeline in the state and do business in 80 of Nebraska’s 93 counties. Residential natural gas distribution pipelines are ever-present in much of the U.S. and distribute natural gas to customers in 79 counties in Nebraska. Large interstate petroleum transmission lines cross under large parts of Nebraska and surrounding states (Figure 1)

Guide for Planning Church Buildings for the Churches of Christ

Describes history, beliefs, church government buildings, and other planning considerations for architects designing for Churches of Christ. Includes bibliography