Experimental Study on a New Type of Transverse Connection for Nebraska County Bridge System

Many county-owned bridges in Nebraska need replacement due to their structural deficiency. Most of the bridges needing replacement are in the 40 to 60 ft range. This span range lacks a standard design that fits Nebraska county practices in terms of speed and simplicity of construction. The current systems being used are (a) Precast 1 by 2 ft planks which can span up to 30 ft, (b) Cast-in-place slab bridges which can span up to 50 ft but require extensive field formwork, concrete placing, and curing, and are best when constructed in three-span units, and (c) Inverted tees which can span 40 to 80 ft, but require cast-in-place decks. The objective of this research project is to develop and evaluate a cross section that can be easily configured for optimal structural efficiency across a range of spans from 40 to 60 feet, while reducing the number of longitudinal shear keys, and retaining the ease of construction presented by the plank design. To achieve this objective, three phases of research were conducted. The first phase included evaluating various sections for spans up to 60 ft. This phase was completed through an extensive literature review and a, new type of cross-section was proposed in this study. The second phase of the research evaluated a new type of transverse connection to connect adjacent units of the proposed cross section for the proposed state county bridge system through small-scale testing on ten slab specimens. Finally, two sets of full-scale bridge specimens were tested to evaluate the system behavior, including the performance of the proposed transverse connection that included the new type of mechanical connection, and staggered rebar splice joints with a commercial high-performance concrete used for the shear key. Test results indicated that the new type of mechanical joint system (transverse connection of adjacent precast beam bridges) can resist an experimental joint moment of 38 ft-kip on average, provided that the maximum spacing between mechanical joints along the bridge span does not exceed 4 ft. It was also noted that the high-performance concrete can carry a joint moment of 17.5 kip-ft per foot length which is 2.5 times larger than the equivalent moment carried by the mechanical joint system with self-consolidating concrete grout. Advisor: Chungwook Si

Cooperative Theory: A Review of Recent Literature

The purpose of this paper is to review the basic economic models used to analyze cooperative organizations. But more importantly the paper attempts to assist the reader in understanding of how cooperatives are either like or unlike Investor-owned businesses. If cooperatives are different, what are the implications of these different member-patrons boards of directors and managment

Land Prices: An Estimate Based on the Capitalized Value Approach

The paper provides a detailed discussion of how the land bid prices were estimated. First, a description of the farm and its cost structure is provided. Second, the implications of the federal farm program to the revenues and costs of the farming operation are discussed. Third, the development of the farming operation\u27s fixed cost estimates are presented. The final section presents the estimated land values and a discussion of the possible outlook for agricultural farm prices

Accounts Receivable Management at Local Cooperatives: A Review of Actual Practices and Strategies for improvement

Accounts receivable represent a major operating expense for local cooperatives. For example, the average local Minnesota cooperative affiliated with a major regional cooperative in 1983 had 35 percent of their total current assets being accounts receivable and credit costs associated with accounts receivable represented 2.5 percent of the credit sales revenue. In contrast, local net savings were only 1.2 percent of sales. Effective accounts receivable management is particularly important in a period of financial stress in agriculture, high interest rates on borrowed capital and narrow local cooperative margins. This paper will review the actual accounts receivable management practices of local cooperatives in southwest Minnesota, eastern South Dakota and northwest Iowa in 1983. These practices will be reviewed relative to standard industry recommendations concerning accounts receivable management strategies. The paper will also provide ideas and suggestions that local cooperatives may consider in their efforts to implement successful accounts receivable management programs

Standard Design for Nebraska County Bridges

Many county-owned bridges in Nebraska need replacement due to their structural deficiency. Most of the bridges needing replacement are in the 40 to 60 ft range. This span range lacks a standard design that fits Nebraska county practices in terms of speed and simplicity of construction. The current systems being used are (a) Precast 1 by 2 ft planks which can span up to 30 ft, (b) Cast-in-place slab bridges which can span up to 50 ft but require extensive field formwork, concrete placing, and curing, and are best when constructed in three-span units, and (c) Inverted tees which can span 40 to 80 ft, but require cast-in-place decks. The objective of this research project is to develop and evaluate a cross section that can be easily configured for optimal structural efficiency across a range of spans from 40 to 60 feet, while reducing the number of shear keys, and retaining the ease of construction presented by the plank design. To achieve this objective, four phases of research were conducted. The first phase included evaluating various sections for spans up to 60 ft. This phase was completed through an extensive literature review and a, new type of cross- section was proposed in this study. The second phase of the research evaluated a new type of transverse connection to connect adjacent units of the proposed cross section for the proposed state county bridge system through small-scale testing on ten slab specimens. The third phase of the research includes testing five sets of full-scale bridge specimens to evaluate the system behavior, including the performance of the proposed transverse connection that included the new type of mechanical connection, staggered rebar splice joints with a commercial high-performance concrete used for the shear key, and full-scale specimen with the staggered splice joint filled with three different types of high performance. Finally, the last phase of the research conducted a design review of various proposed sections and generated span charts that could be implemented for Nebraska County bridge design. Test results indicated that the new type of mechanical joint system (transverse connection of adjacent precast beam bridges) can resist an experimental joint moment of 38 ft-kip on average, provided that the maximum spacing between mechanical joints along the bridge span does not exceed 4 ft. It was also noted that the high-performance concrete can carry a joint moment of 17.5 kip-ft per foot length which is 2.5 times larger than the equivalent moment carried by the mechanical joint system with self-consolidating concrete grout. Other possible designs that were not tested through the small scale or full-scale experimental program were proposed by a local engineering firm in Omaha and reviewed in this research. The final standard design and design span charts are proposed for Nebraska County Bridges based on literature review, small scale testing, full-scale testing, and engineering calculations

Mapping agricultural land abandonment from spatial and temporal segmentation of Landsat time series

© 2018 Elsevier Inc. Agricultural land abandonment is a common land-use change, making the accurate mapping of both location and timing when agricultural land abandonment occurred important to understand its environmental and social outcomes. However, it is challenging to distinguish agricultural abandonment from transitional classes such as fallow land at high spatial resolutions due to the complexity of change process. To date, no robust approach exists to detect when agricultural land abandonment occurred based on 30-m Landsat images. Our goal here was to develop a new approach to detect the extent and the exact timing of agricultural land abandonment using spatial and temporal segments derived from Landsat time series. We tested our approach for one Landsat footprint in the Caucasus, covering parts of Russia and Georgia, where agricultural land abandonment is widespread. First, we generated agricultural land image objects from multi-date Landsat imagery using a multi-resolution segmentation approach. Second, we estimated the probability for each object that agricultural land was used each year based on Landsat temporal-spectral metrics and a random forest model. Third, we applied temporal segmentation of the resulting agricultural land probability time series to identify change classes and detect when abandonment occurred. We found that our approach was able to accurately separate agricultural abandonment from active agricultural lands, fallow land, and re-cultivation. Our spatial and temporal segmentation approach captured the changes at the object level well (overall mapping accuracy = 97 ± 1%), and performed substantially better than pixel-level change detection (overall accuracy = 82 ± 3%). We found strong spatial and temporal variations in agricultural land abandonment rates in our study area, likely a consequence of regional wars after the collapse of the Soviet Union. In summary, the combination of spatial and temporal segmentation approaches of time-series is a robust method to track agricultural land abandonment and may be relevant for other land-use changes as well

Declining human pressure and opportunities for rewilding in the steppes of Eurasia

Large and ecologically functioning steppe complexes have been lost historically across the globe, but recent land‐use changes may allow the reversal of this trend in some regions. We aimed to develop and map indicators of changing human influence using satellite imagery and historical maps, and to use these indicators to identify areas for broad‐scale steppe rewilding.Peer Reviewe

Reducing persecution is more effective for restoring large carnivores than restoring their prey

We gratefully acknowledge funding by the Federal State of Berlin, Germany (Elsa Neumann Scholarship to BB), and the German Research Foundation (GH 149/1-1 and ZU 361/1-1). We further thank all participants of the workshop on the revi- sion of the Strategy for Leopard Conservation in the Caucasus in Tbilisi, Georgia in 2017. We are grateful to J. Buchner, A. Heidelberg, V.C. Radeloff, and H. Yin for fruitful discussions, and F. Poetzschner for help with preparing data. Additionally, we thank two anonymous reviewers for their constructive comments.Peer reviewedPublisher PD

Fostering large carnivore recoveries: Persian leopards and their prey in the Caucasus

Weltweit sind viele Populationen großer Raubtiere bedroht. Die Suche nach Wegen zur Erhaltung und Wiederherstellung von Populationen großer Raubtiere ist daher ein zentrales Naturschutzziel. In einigen Regionen erholen sich die Populationen jedoch auch, was der Wissenschaft eine hervorragende Möglichkeit bietet potentielle Wege zum Schutz von Raubtieren zu identifizieren. Das Ziel dieser Arbeit war es, die Voraussetzungen, die eine Erholung von Raubtierpopulationen begünstigen, besser zu verstehen. Am Beispiel der sich erholenden Population des Persischen Leoparden im Kaukasus beantwortet diese Arbeit die folgenden Forschungsfragen: (1) Bietet die Ökoregion des Kaukasus einen geeigneten, sicheren und zusammenhängenden Lebensraum für Persische Leoparden und ihre Beutetiere? (2) Was sind wirksame Schutzstrategien, die eine Erholung der Population des Persischen Leoparden im Kaukasus begünstigen? Die Ergebnisse dieser Arbeit lassen den Schluss zu, dass für Leoparden und ihre Beutetiere im Kaukasus großflächig geeigneter Lebensraum vorhanden ist. Trotz dieser günstigen Ausgangsposition für den Artenschutz zeigt diese Arbeit jedoch auch klar auf, dass Schutzmaßnahmen erforderlich sind, um direkte Bedrohungen abzumildern. Als wichtigsten Faktor für eine Erholung der Leopardenpopulation identifiziert diese Arbeit das Verhindern von Tötungen. Diese Arbeit verdeutlicht somit die wichtige Rolle von Konfliktminderung zwischen Menschen und Raubtieren, um die daraus resultierende Tötung von Raubtieren zu verhindern. Darüber hinaus unterstreicht diese Dissertation die Notwendigkeit der Vernetzung sicherer Lebensräume und den Wert von internationaler Zusammenarbeit zur Förderung der Genesung von Populationen großer Raubtiere. Zusammengefasst liefert diese Arbeit Einblicke in Bedingungen, die die Genesung von Großraubtieren fördern, und umreißt mögliche zukünftige Wege eines vom Aussterben bedrohten Raubtiers in einem globalen Biodiversitäts-Hotspot.Large carnivore populations are threatened globally. This is worrisome because of their intrinsic value and their importance for ecosystems and humans. Finding ways to maintain and restore large carnivore populations is therefore a central goal for conservation. Interestingly, large carnivores are also returning to areas where they were extirpated before, which provides a great opportunity for conservation science to identify pathways to safeguard large carnivore populations. The overall goal of this thesis was to better understand the conditions that foster large carnivore recoveries. Gaining a better understanding of large carnivore recoveries is challenging though, because it requires working across broad areas, where data on environmental characteristics and prey species is often limited and inconsistent. Using the Persian leopard recovery in the Caucasus ecoregion as an example, the specific research questions of this thesis were: (1) Does the Caucasus ecoregion have suitable, safe, and connected habitat for Persian leopards and their prey? (2) What are effective management strategies to foster the recovery of Persian leopards in the Caucasus? Results revealed that suitable habitat for Persian leopards and their prey is widespread in the Caucasus. However, habitat patches are often not safe and conservation efforts are needed to mitigate threats and restore, protect, and connect populations of leopards and their prey. Reducing the persecution of leopards seems the most important strategy to foster leopard recovery in the Caucasus. For large carnivore recoveries in general, this thesis underpins the importance of human-carnivore conflict mitigation to prevent killings of carnivores, particularly in areas where populations are small. Further, this thesis underlines the need of improving connectivity among safe habitat patches and the value of international cooperation. Overall, this thesis provides insights into conditions that foster large carnivore recovery and outlines potential future pathways for a critically endangered apex predator in a global biodiversity hotspot

Standard Design for Nebraska County Bridges

Many county-owned bridges in Nebraska need replacement due to their structural deficiency. Most of the bridges needing replacement are in the 40 to 60 ft range. This span range lacks a standard design that fits Nebraska county practices in terms of speed and simplicity of construction. The current systems being used are (a) Precast 1 by 2 ft planks which can span up to 30 ft, (b) Cast-in-place slab bridges which can span up to 50 ft but require extensive field formwork, concrete placing, and curing, and are best when constructed in three-span units, and (c) Inverted tees which can span 40 to 80 ft, but require cast-in-place decks. The objective of this research project is to develop and evaluate a cross section that can be easily configured for optimal structural efficiency across a range of spans from 40 to 60 feet, while reducing the number of shear keys, and retaining the ease of construction presented by the plank design. To achieve this objective, four phases of research were conducted. The first phase included evaluating various sections for spans up to 60 ft. This phase was completed through an extensive literature review and a, new type of cross- section was proposed in this study. The second phase of the research evaluated a new type of transverse connection to connect adjacent units of the proposed cross section for the proposed state county bridge system through small-scale testing on ten slab specimens. The third phase of the research includes testing five sets of full-scale bridge specimens to evaluate the system behavior, including the performance of the proposed transverse connection that included the new type of mechanical connection, staggered rebar splice joints with a commercial high-performance concrete used for the shear key, and full-scale specimen with the staggered splice joint filled with three different types of high performance. Finally, the last phase of the research conducted a design review of various proposed sections and generated span charts that could be implemented for Nebraska County bridge design. Test results indicated that the new type of mechanical joint system (transverse connection of adjacent precast beam bridges) can resist an experimental joint moment of 38 ft-kip on average, provided that the maximum spacing between mechanical joints along the bridge span does not exceed 4 ft. It was also noted that the high-performance concrete can carry a joint moment of 17.5 kip-ft per foot length which is 2.5 times larger than the equivalent moment carried by the mechanical joint system with self-consolidating concrete grout. Other possible designs that were not tested through the small scale or full-scale experimental program were proposed by a local engineering firm in Omaha and reviewed in this research. The final standard design and design span charts are proposed for Nebraska County Bridges based on literature review, small scale testing, full-scale testing, and engineering calculations