Hydro-economic modelling of groundwater-fed irrigation

Expansion of groundwater-fed irrigation has enhanced agricultural productivity, while simultaneously causing large reductions in groundwater storage. Hydro-economic modelling provides a valuable tool for evaluating trade-offs between agriculture and aquifer sustainability. However, a central argument in this thesis is that the reliability of integrated analysis of groundwater systems may be affected by the failure to consider adequately the variables influencing field-level irrigation decisions and the dynamic aquifer responses to those choices. This thesis addresses this limitation of existing research through three main contributions to the literature. In Chapter 2, a new model of farmers’ individual field-level groundwater-fed irrigation decision making is developed. Innovations include the explicit consideration of the role of soil moisture in intraseasonal irrigation scheduling, and evaluation of the impacts of weather variability and well yield on crop production. Application to a case study in the High Plains region of the United States demonstrates that low well yields limit significantly irrigated area and demand for groundwater. Furthermore, it is shown that this important behavioural response can not be captured by existing models that do not consider instantaneous supply constraints imposed by well yield. In Chapter 3, a combination of empirical analysis of observation data, and numerical simulations using the model developed in Chapter 2, are conducted to generate insights about the feedbacks between groundwater and agriculture. Reductions in well yield are shown to have large negative impacts on the productivity of irrigation whereas, contrary to previous assumptions, the response of irrigation behaviour to increased groundwater pumping lifts is found to be minimal. Importantly, this result highlights the need for integrated models to consider a broader range of factors influencing the sustainability of agricultural groundwater use. In Chapter 4, a novel hydro-economic modelling framework is presented that integrates the model of farmers’ individual irrigation decision making with a distributed multi-scale groundwater flow model. The model extends the scope of existing research by using pump head-capacity curves to quantify the effect of changing aquifer storage on well yields. Advantages of the modelling framework for policy analysis in coupled agricultural groundwater systems are demonstrated. Specifically, it is shown that the long-term sustainability of irrigated agriculture is influenced by intraseasonal and interannual changes in well yield that depend on famers’ pump choice and expectations about future dynamic aquifer responses. Moreover, the model demonstrates that managing the rate of well yield decline may have positive long-term impacts on both agricultural production and farmer welfare that have not been recognised in previous research.Open Acces

Real-time stress analysis of three-dimensional boundary element problems with continuously updating geometry

Computational design of mechanical components is an iterative process that involves multiple stress analysis runs; this can be time consuming and expensive. Significant improvements in the efficiency of this process can be made by increasing the level of interactivity. One approach is through real-time re-analysis of models with continuously updating geometry. In this work the boundary element method is used to realise this vision. Three primary areas need to be considered to accelerate the re-solution of boundary element problems. These are re-meshing the model, updating the boundary element system of equations and re-solution of the system. Once the initial model has been constructed and solved, the user may apply geometric perturbations to parts of the model. A new re-meshing algorithm accommodates these changes in geometry whilst retaining as much of the existing mesh as possible. This allows the majority of the previous boundary element system of equations to be re-used for the new analysis. Efficiency is achieved during re-integration by applying a reusable intrinsic sample point (RISP) integration scheme with a 64-bit single precision code. Parts of the boundary element system that have not been updated are retained by the re-analysis and integrals that multiply zero boundary conditions are suppressed. For models with fewer than 10,000 degrees of freedom, the re-integration algorithm performs up to five times faster than a standard integration scheme with less than 0.15% reduction in the L_2-norm accuracy of the solution vector. The method parallelises easily and an additional six times speed-up can be achieved on eight processors over the serial implementation. The performance of a range of direct, iterative and reduction based linear solvers have been compared for solving the boundary element system with the iterative generalised minimal residual (GMRES) solver providing the fastest convergence rate and the most accurate result. Further time savings are made by preconditioning the updated system with the LU decomposition of the original system. Using these techniques, near real-time analysis can be achieved for three-dimensional simulations; for two-dimensional models such real-time performance has already been demonstrated

The matching law

This article introduces the quantitative analysis of choice behavior by describing a number of equations developed over the years to describe the relation between the allocation of behavior under concurrent schedules of reinforcement and the consequences received for alternative responses. Direct proportionality between rate of responding and rate of reinforcement was observed in early studies, suggesting that behavioral output matched environmental input in a mathematical sense. This relation is termed "strict matching," and the equation that describes it is referred to as "the matching law." Later data showed systematic departures from strict matching, and a generalized version of the matching equation is now used to describe such data. This equation, referred to as "the generalized matching equation," also describes data that follow strict matching. It has become convention to refer to either of these equations as "the matching law." Empirical support for the matching law is briefly summarized, as is the applied and practical significance of matching analyses

Oncologic outcomes following surgical management of clinical stage II sex cord stromal tumors

Objective To investigate the clinical history of patients with clinical stage II sex cord stromal tumors who underwent RPLND at our institution. Methods Our prospectively maintained testicular cancer database was queried to identify patients who presented with or developed clinical stage II sex cord stromal tumors and underwent RPLND at our institution between 1980 and 2018. Demographic, clinical and pathological characteristics were reviewed. Kaplan-Meier curves were graphed to assess recurrence-free and overall survival. Results Fourteen patients were included in the study with a median age of 44.2 years. Four patients presented with clinical stage II disease and 10 patients developed metastatic disease during follow-up of initial clinical stage I disease with a median time to metastasis of 2.7 years (range: 0.4-19.5 years). Of the 10 patients with orchiectomy pathology data available, all patients had at least 1 risk factor on testis pathology (mean: 2.9 risk factors). Nine patients received treatment prior to referral to our institution. All patients recurred post-RPLND at Indiana University. Median recurrence-free survival was 9.8 months. Twelve patients died of disease with a median overall survival of 14.4 months. Conclusions Metastatic sex cord stromal tumors are rare and are more resistant to standard treatment modalities than metastatic germ cell tumors. Patients presenting with sex cord stromal tumors should consider prophylactic primary RPLND in the setting of one or more pathological predictor of malignancy

Miss Manners: A Specialized Silicon Compiler for Synchronizers

Miss Manners is a synchronizer generator that will produce the layout of a synchronizer given a high-level description. A synchronizer generator is a type of specialized silicon compiler. Synchronizer generators can greatly aid the design of systems that are structured as loosely-coupled networks of autonomous subsystems. Chips that are structured in this way have reduced communication requirements and greater tolerance for transient failures. We describe a language for specifying synchronization requirements and a compiler for translating the language into circuits that enforce the specifications

GRASSLAND DIVERSITY AND PRODUCTIVITY: THE INTERPLAY OF RESOURCE AVAILABILITY AND PROPAGULE POOLS

Processes operating at multiple spatial scales govern the structure and functioning of ecological communities. We conducted a resource manipulation and propagule addition experiment in grassland to evaluate the interaction of local resource availability and propagule pools in governing local-scale plant colonization, biodiversity, and above-ground productivity. The availabilities of establishment microsites and water were manipulated in field plots for two years through the application of experimental soil disturbances and irrigation, respectively. Resource manipulations led to increased invasibility of the community, as predicted by the theory of fluctuating resources. Rates of colonization,enhanced by the sowing of 32 grassland species, increased plant diversity and above ground productivity, but to a greater extent under conditions of resource enrichment. Although resource enrichment generally increased diversity and productivity, these responses were contingent upon species availability and tended to be more pronounced in the presence of an expanded propagule pool. These findings suggest that biodiversity at the level of the available propagule pool and fluctuations in resources interact to regulate local resident diversity and productivity by determining opportunities for species sorting, by mediating community assembly, and by governing the potential for functional compensation in the community

Contacts

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Exploring coping strategies of transfer students joining universities from colleges

Students transitioning from colleges to universities in the United Kingdom (UK) into the second or third year of an undergraduate programme must quickly adapt to a new learning environment and new expectations. The process of transition includes intense demands on their time and, for many, a requirement to commute. The consequence can be a limited university experience compared to those who began their studies in the traditional first year. With the increase in the numbers of transfer students studying at universities in the UK, this study was set up to explore the challenges of transition at two universities using an online survey and focus groups. Results show that transfer students cope with their transition to university in multiple ways, categorised into the following themes: learning expectations, peer support, online engagement, cue-seeking and efficiency. By supporting the use of these coping strategies, universities can facilitate a better student experience and enhance student success.Publisher PDFPeer reviewe