A distributed accelerated gradient algorithm for distributed model predictive control of a hydro power valley

A distributed model predictive control (DMPC) approach based on distributed optimization is applied to the power reference tracking problem of a hydro power valley (HPV) system. The applied optimization algorithm is based on accelerated gradient methods and achieves a convergence rate of O(1/k^2), where k is the iteration number. Major challenges in the control of the HPV include a nonlinear and large-scale model, nonsmoothness in the power-production functions, and a globally coupled cost function that prevents distributed schemes to be applied directly. We propose a linearization and approximation approach that accommodates the proposed the DMPC framework and provides very similar performance compared to a centralized solution in simulations. The provided numerical studies also suggest that for the sparsely interconnected system at hand, the distributed algorithm we propose is faster than a centralized state-of-the-art solver such as CPLEX

Distributed Model Predictive Control of a Hydro-Power Valley by Dual Decomposition

International audienceIn this paper, a suboptimal distributed MPC approach for linear interconnected systems is considered, where it is assumed that the systems are coupled through their control inputs and an optimal reference tracking problem for the overall system is solved. The approach is applied to distributed MPC of a hydro-power valley case study

Medical Image Segmentation Using Phase-Field Method based on GPU Parallel Programming

The use of a Phase Field method for medical image segmentation is proposed in this paper. The Allen-Cahn equation, a mathematical model equation, is used in this method. The Finite Difference method is used for numerical discretization of model equations and semi-algebraic equations integrated over time using the second -order Runge-Kutta method. Numerical algorithms are implemented into computer programming using the serial and parallel C programming language based on GPU CUDA. Based on image segmentation calculations, the Phase Field method has high accuracy. It is indicated by the Jaccard Index and Dice Similarity values that are close to one. The range of Jaccard Index values is 0.859 - 0.952, while the Dice Similarity value range is 0.926 - 0.976. In addition, it is shown that parallel programming with GPU CUDA can accelerate 45.72 times compared to serial programming

Development of a Parsimonious Urban Landscape Nutrient Model using Representations of Terrestrial Denitrification Controls

Nonpoint source pollution of nitrogen (N) and phosphorus (P) creates pervasive water quality and eutrophication problems around the world, adversely affecting rivers, lakes, and estuaries. Urban land use generates excess N and P pollutants and land use conversion removes natural N and P filtration services provided by undeveloped ecosystems. Management of these problems might first be approached using scoping level nonpoint source runoff models that are defined as balancing process complexity and algorithm simplicity, as well as balancing data availability and predictive accuracy. The contributing area / dispersal area (CADA) concept brings land cover and elevation data along with runoff and filtering likelihood algorithms into the Export Coefficient (EC) model to map likely variations in nutrient loading across the landscape. In this research, we enhance scoping level models by 1) adding spatial variation through the mapping of runoff and buffering likelihoods, 2) introducing the temporal driver of rainfall intensity to enhance nutrient export, and 3) determining the environmental variables most highly correlated with denitrification. In this study, we enhance the EC model to account for spatial and temporal variations, allowing for better estimates of nutrient loading across space and time. This research also determines key predictors of denitrification potential in mixed-use watersheds, through which denitrification hotspots can be identified. The creation of spatially- and temporally-distributed scoping models for nutrient loading through the landscape will assist managers in identifying areas of high loading potential, which generate high concentrations of nutrients and have little opportunity for downslope filtration. The identification of high denitrification potential zones also allows for facilitation of nitrate removal by routing nitrate-rich water to these zones. The low-level data needs and process-based features of the scoping model allow for its implementation into the i-Tree Hydro toolkit, a peer-reviewed software suite that is used to assess the effects of management and land use change on water quality and quantity

Spatial prediction of landslide susceptibility/intensity through advanced statistical approaches implementation: applications to the Cinque Terre (Eastern Liguria, Italy)

Landslides are frequently responsible for considerable huge economic losses and casualties in mountainous regions especially nowadays as development expands into unstable hillslope areas under the pressures of increasing population size and urbanization (Di Martire et al. 2012). People are not the only vulnerable targets of landslides. Indeed, mass movements can easily lay waste to everything in their path, threatening human properties, infrastructures and natural environments. Italy is severely affected by landslide phenomena and it is one of the most European countries affected by this kind of phenomena. In this framework, Italy is particularly concerned with forecasting landslide effects (Calcaterra et al. 2003b), in compliance with the National Law n. 267/98, enforced after the devastating landslide event of Sarno (Campania, Southern Italy). According to the latest Superior Institute for the Environmental Protection and Research (ISPRA, 2018) report on "hydrogeological instability" of 2018, it emerges that the population exposed to landslides risk is more than 5 million and in particular almost half-million falls into very high hazard zones. The slope stability can be compromised by both natural and human-caused changes in the environment. The main reasons can be summarised into heavy rainfalls, earthquakes, rapid snow-melts, slope cut due to erosions, and variation in groundwater levels for the natural cases whilst slopes steepening through construction, quarrying, building of houses, and farming along the foot of mountainous zone correspond to the human component. This Ph.D. thesis was carried out in the Liguria region, inside the Cinque Terre National Park. This area was chosen due to its abundance of different types of landslides and its geological, geomorphological and urban characteristics. The Cinque Terre area can be considered as one of the most representative examples of human-modified landscape. Starting from the early centuries of the Middle Ages, local farmers have almost completely modified the original slope topography through the construction of dry-stone walls, creating an outstanding terraced coastal landscape (Terranova 1984, 1989; Terranova et al. 2006; Brandolini 2017). This territory is extremely dynamic since it is characterized by a complex geological and geomorphological setting, where many surficial geomorphic processes coexist, along with peculiar weather conditions (Cevasco et al. 2015). For this reason, part of this research focused on analyzing the disaster that hit the Cinque Terre on October, 25th, 2011. Multiple landslides took place in this occasion, triggering almost simultaneously hundreds of shallow landslides in the time-lapse of 5-6 hours, causing 13 victims, and severe structural and economic damage (Cevasco et al. 2012; D\u2019Amato Avanzi et al. 2013). Moreover, this artificial landscape experienced important land-use changes over the last century (Cevasco et al. 2014; Brandolini 2017), mostly related to the abandonment of agricultural activity. It is known that terraced landscapes, when no longer properly maintained, become more prone to erosion processes and mass movements (Lesschen et al. 2008; Brandolini et al. 2018a; Moreno-de-las-Heras et al. 2019; Seeger et al. 2019). Within the context of slope instability, the international community has been focusing for the last decade on recognising the landslide susceptibility/hazard of a given area of interest. Landslide susceptibility predicts "where" landslides are likely to occur, whereas, landslide hazard evaluates future spatial and temporal mass movement occurrence (Guzzetti et al., 1999). Although both definitions are incorrectly used as interchangeable. Such a recognition phase becomes crucial for land use planning activities aimed at the protection of people and infrastructures. In fact, only with proper risk assessment governments, regional institutions, and municipalities can prepare the appropriate countermeasures at different scales. Thus, landslide susceptibility is the keystone of a long chain of procedures that are actively implemented to manage landslide risk at all levels, especially in vulnerable areas such as Liguria. The methods implemented in this dissertation have the overall objective of evaluating advanced algorithms for modeling landslide susceptibility. The thesis has been structured in six chapters. The first chapter introduces and motivates the work conducted in the three years of the project by including information about the research objectives. The second chapter gives the basic concepts related to landslides, definition, classification and causes, landslide inventory, along with the derived products: susceptibility, hazard and risk zoning, with particular attention to the evaluation of landslide susceptibility. The objective of the third chapter is to define the different methodologies, algorithms and procedures applied during the research activity. The fourth chapter deals with the geographical, geological and geomorphological features of the study area. The fifth chapter provides information about the results of the applied methodologies to the study area: Machine Learning algorithms, runout method and Bayesian approach. Furthermore, critical discussions on the outcomes obtained are also described. The sixth chapter deals with the discussions and the conclusions of this research, critically analysing the role of such work in the general panorama of the scientific community and illustrating the possible future perspectives

Control by Vegetation Disturbance on Gully Rejuvenation Following Wildfire

Gully rejuvenation (GR) following wildfire influences landform evolution and generates flooding and debris that alters aquatic habitat and threatens human activities. Fire severity, defined as the degree of vegetation loss by wildfire, is a hypothesized control on this erosion response. I investigated three related aspects of the relationship between fire severity and GR: The capacity of vegetation disturbance to explain the occurrence or non-occurrence of GR; the spatial structure of burn mosaics relative to post-fire erosion; and the relationship between fire severity and threshold conditions required for channel initiation. I surveyed 269 burned catchments and mapped 111 cases of GR across sites in Montana and Idaho. I created the Vegetation Disturbance Index (VDI) derived from LANDSAT images to quantify fire severity and implemented geospatial and statistical analysis to quantify relationships between VDI and post-fire erosion response. Vegetation disturbance strongly explained GR with additional influences from upslope geometry and pre-fire shrub cover. As fire severity increased, the percent of the catchment area covered by continuous patches of high severity burn increased non-linearly. Trends in patch structure defined a threshold of fire severity after which the probability of GR was strongly correlated with the development of large, continuous severely burned patches. Fire severity systematically influenced the relationship between source area and steepness. Threshold conditions for channel initiation, specifically source area steepness and curvature, decreased as vegetation disturbance increased. These results provide inferential evidence that vegetation disturbance exerts first-order controls over post-fire erosion processes. The results of the patch-pattern analysis suggest that progressive loss of vegetation due to wildfire leads to critical thresholds of hydrologic connectivity after which runoff and erosion accelerate. The source area analysis suggests that forces of convergent flow are not fully expressed until a significant proportion of vegetation has been consumed such that flow resistance is minimized. The VDI as a continuous metric of vegetation disturbance may contribute to improved quantitative analysis of landform evolution relative to vegetation disturbance, ecological effects of fire, and ecosystem response to climate change. The assessment methodology outlined herein provides a first step towards a systematic quantification of the potential for GR following wildfire

International Conference on Continuous Optimization (ICCOPT) 2019 Conference Book

The Sixth International Conference on Continuous Optimization took place on the campus of the Technical University of Berlin, August 3-8, 2019. The ICCOPT is a flagship conference of the Mathematical Optimization Society (MOS), organized every three years. ICCOPT 2019 was hosted by the Weierstrass Institute for Applied Analysis and Stochastics (WIAS) Berlin. It included a Summer School and a Conference with a series of plenary and semi-plenary talks, organized and contributed sessions, and poster sessions. This book comprises the full conference program. It contains, in particular, the scientific program in survey style as well as with all details, and information on the social program, the venue, special meetings, and more

Dynamic Optimization Algorithms for Baseload Power Plant Cycling under Variable Renewable Energy

The growing deployment of variable renewable energy (VRE) sources, such as wind and solar, is mainly due to the decline in the cost of renewable technologies and the increase of societal and cultural pressures. Solar and wind power generation are also known to have zero marginal costs and fuel emissions during dispatch. Thereby, the VRE from these sources should be prioritized when available. However, the rapid deployment of VRE has heightened concerns regarding the challenges in the integration between fossil-fueled and renewable energy systems. The high variability introduced by the VRE as well as the limited alignment between demand and wind/solar power generation led to the increased need of dispatchable energy sources such as baseload natural gas- and coal-fired power plants to cycle their power outputs more often to reliably supply the net load. The increasing power plant cycling can introduce unexpected inefficiencies into the system that potentially incur higher costs, emissions, and wear-and-tear, as the power plants are no longer operating at their optimal design points. In this dissertation, dynamic optimization algorithms are developed and implemented for baseload power plant cycling under VRE penetration. Specifically, two different dynamic optimization strategies are developed for the minute and hourly time scales of grid operation. The minute-level strategy is based on a mixed-integer linear programming (MILP) formulation for dynamic dispatch of energy systems, such as natural gas- and coal-fired power plants and sodium sulfur batteries, under VRE while considering power plant equipment health-related constraints. The hourly-level strategy is based on a Nonlinear Multi-objective dynamic real-time Predictive Optimization (NMPO) implemented in a supercritical pulverized coal-fired (SCPC) power plant with a postcombustion carbon capture system (CCS), considering economic and environmental objectives. Different strategies are employed and explored to improve computational tractability, such as mathematical reformulations, automatic differentiation (AD), and parallelization of a metaheuristic particle swarm optimization (PSO) component. The MILP-based dynamic dispatch framework is used to simulate case studies considering different loads and renewable penetration levels for a suite of energy systems. The results show that grid flexibility is mostly provided by the natural gas power plant, while the batteries are used sparingly. Additionally, considering the post-optimization equivalent carbon analysis, the environmental performance is intrinsically connected to grid flexibility and the level of VRE penetration. The stress results reinforce the necessity of further considering and including equipment health-related constraints during dispatch. The results of the NMPO successfully implemented for a large-scale SCPC-CCS show that the optimal compromise is automatically chosen from the Pareto front according to a set of weights for the objectives with minimal interaction between the framework and the decision maker. They also indicate that to setup the optimization thresholds and constraints, knowledge of the power system operations is essential. Finally, the market and carbon policies have an impact on the optimal compromise between the economic and environmental objectives

MORPHODYNAMICS AND SEDIMENT TRANSFER IN A HUMAN-IMPACTED ALPINE RIVER

In the Anthropocene, river basins have been affected by human impact both indirectly, e.g. through changes in climate and land-use, and directly, e.g. through river engineering and flow management. The Swiss Rhône basin is a notable example, where its Alpine tributaries are heavily impacted upon by climate warming and hydro-electric power exploitation (hydropower). Upstream, the Rhône’s catchment is responding to the accelerated release of unconsolidated sediment associated with a history of glacial recession and ongoing climate change. In parallel, there is extensive abstraction of flow for hydropower, a common practice throughout the European Alps, which strongly reduces river sediment transport capacity whilst, contrary to classical reservoir dams, maintains sediment supply to streams. Combined, these impacts affect the morphodynamics and sediment storage of Alpine streams and hence the downstream transfer of sediment to the main rivers such as the Rhône.In this thesis, the morphodynamics and sediment transfer of a left bank tributary of the Rhône, the Borgne d’Arolla, are studied in response to the combined effects of climate change and flow abstraction. The river has a strongly regulated flow with c. 90% of water abstracted at intakes. The intakes have to be flushed of sediment and most flow then occurs as a result of this short duration (typically 30 minutes to 2 hours) flushing. Additional flow can occur if the upstream water transfer tunnels are full and the intake has to be opened for longer duration. The result is that the stream bed is dry for most of the time, but perturbed by flushing events. This makes the field site well adapted for the quantification of morphological change, through the remote sensing of the dry braided river bed at timescales from the daily to the decadal. It also allows provides high quality flow records at the intakes, which also record flushing, and so allow reconstruction of sediment supply rates from the 1970s. The river bed level evolution since the onset of flow abstraction in the early 1960s was analysed through the development of Structure from Motion (SfM) photogrammetric techniques for application to archival imagery. This partly automated methodology allows for the generation of detailed and accurate historical Digital Elevation Models (DEMs), although it requires the careful consideration of photogrammetric principles, particularly in low-relief environments such as braided rivers. Over shorter timescales (daily) the river morphodynamics were monitored using a long-range terrestrial laser scanner. The reaches just below the main intake show considerable aggradation (up to 5 meters) since the onset of flow abstraction. Widespread aggradation however did not commence until the onset of glacier retreat in the late 1980s and the dry and notably warm years of the early 1990s which intake records suggest led to an increase in upstream sediment supply. Surprisingly, most of the supplied sediment (c. 75%) was transferred through the studied reaches despite flow abstraction reducing transport capacity by an order of magnitude. This was because the natural transport capacity was substantially greater than sediment supply rates such that the reduction in capacity due to abstraction still allowed significant sediment flux. However, abstraction rendered the system more sensitive to internal and external forcing, whether ‘natural’ or human-induced. The spatial and temporal distribution of sediment transport and morphological change within the reaches varies strongly between events with similar levels of forcing (imposed flow and sediment supply). This stresses the importance of antecedent conditions, i.e. river bed topography and sediment stored, and internal morphological feedbacks on sediment transport rates and challenges simplistic notions regarding the equilibrium morphology in these systems. The system sensitivity also leads to the rapid response of the river to climate-driven hydrological variability and climate induced changes in sediment delivery rates and intake system functioning. The flow abstraction itself was designed under different climatic conditions such that the transfer tunnels are no longer sufficient to transport all glacial melt under extreme summer temperatures. This led to a strong increase in non- regulated flood events when the intake is opened for longer durations of time. The onset of these events has had a major impact on the downstream export of sediment from the reaches. In the wider river basin, the climate driven increases in sediment supply are conveyed downstream and reflected in: (1) temporal trends in sediment mining in the tributary basin; (2) the abundance of headwater sediments in the river bed sediment composition near the tributary outlet; and (3) increasing suspended load at the outlet of the Rhône in Lake Geneva. -- Au cours de l’Anthropocène, les bassins versants alpins ont été affectés par les activités humaines de manière indirecte, via les changements climatiques et l’évolution des usages du sol, et directement à travers l’ingénierie des cours d’eau et la régulation des débits. Le bassin du Rhône suisse est un exemple notoire, ses tributaires alpins étant significativement impacté par le réchauffement climatique et l’exploitation hydroélectrique. Les environnements alpins s’adaptent en réponse à l’accélération du taux de livraison de sédiments non-consolidés depuis l’amont en lien avec la récession glaciaire récente et les changements climatiques en cours. Parallèlement, beaucoup de bassins versants alpins sont affectés par des prélèvements d’eau pour l’exploitation hydroélectrique. Cette pratique, commune à travers la chaine alpine, réduit drastiquement la capacité de transport des cours d’eau tout en laissant dans le lit l’entier de la masse sédimentaire, contrairement aux lacs de barrage qui tendent à stocker les matériaux et produire des déficits sédimentaires à l’aval. Combinés, les impacts des changements climatiques et des prélèvements d’eau affectent ainsi la dynamique morphologique, la capacité de stockage et la capacité de transfert des tributaires alpins vers les émissaires principaux, le Rhône dans ce cas précis. Dans ce travail de thèse, ce sont la dynamique morphologique et les transferts sédimentaires de la Borgne d’Arolla, tributaire du Rhône, qui ont été étudiés en réponse aux effets combinés des changements climatiques et des prélèvements d’eau pour la production hydroélectrique. Le caractère intermittent et hautement régulé des écoulements permet la quantification précise des changements morphologiques à travers la télédétection du lit pendant les périodes sèches où le débit est nul, et la reconstruction du taux de livraison sédimentaire depuis les années 1970 est rendue possible par les données de purge des captages. L’évolution du lit de la Borgne depuis le début de l’exploitation hydroélectrique au début des années 1960 a été étudié à travers l’application de méthodes photogrammétriques ‘Structure from Motion’ à des images aériennes historiques. Cette méthode semi-automatique permet la production de modèles numériques de terrain historiques à haute résolution (MNTs), où la faible amplitude altitudinale des plaines alluviales alpines requière un contrôle consciencieux des résultats photogrammétriques. Les résultats de l’étude montrent que le tronçon situé directement en aval du captage principal a subi une aggradation considérable (jusqu’à 5 mètres) depuis le début des prélèvements d’eau.L’aggradation du lit à plus large échelle n’a toutefois pas débuté jusqu’à l’initiation du retrait glaciaire à la fin des années 1980 et au cours des années particulièrement chaudes du début des années 1990 qui ont conduit à une augmentation dans le taux de livraison sédimentaire depuis l’amont. Malgré cela, les données montrent que la majeure partie des sédiments (environ 75%) ont pu être transférés à travers le tronçon d’étude. En effet, si les prélèvements d’eau ont significativement réduit la capacité de transport de la Borgne, il apparait que la capacité de transport résiduelle reste proche du taux de livraison depuis l’amont. Cet équilibre rend le système hautement sensible aux forçages internes et externes, qu’ils soient ‘naturels’ ou anthropiques. La distribution spatiale et temporelle du transport sédimentaire et les changements morphologiques au sein des tronçons étudiés varient significativement entre des séquences intermittentes d’écoulement qui correspondent à des ‘purges sédimentaires’ des captages d’eau. Ceci souligne l’importance des conditions antérieures à la purge à l’aval du captage, notamment la morphologie des chenaux de la plaine alluviale et le stockage des sédiments en leur sein, ainsi que leurs rétroactions sur les taux de transport, pour la compréhension de l’équilibre morphologique de ces systèmes. La sensibilité du système conduit également à des réponses rapides face aux forçages externes liés aux changements climatiques et hydrologiques dans le bassin versant, notamment l’évolution des taux de livraison sédimentaire et la fréquence des purges des captages d’eau qui avait été dimensionnés par le passé sur la base de conditions climatiques plus froides. Ceci conduit à une forte augmentation de la fréquence des crues non régulées en raison de la surcharge du système de captage et de transfert des eaux, ce qui impacte significativement l’export de sédiment vers l’aval. Dans le bassin versant à plus large échelle, l’augmentation du taux de livraison sédimentaire dû aux changements climatiques et sa propagation peuvent être perçus: (1) dans la variabilité temporelle des prélèvements de matériaux dans les carrières du bassin versant; (2) dans le volume des cônes de déjection à la confluence des tributaires avec les émissaires principaux; et (3) dans l’augmentation de la charge en suspension dans le delta du Rhône sur le lac Léman