Understanding the Behavior of Embankment Dams Under Blast Loading

This purpose of this study is to investigate the deformation-induced stability of earthen embankment dams to explosive airblast loading. This study specifically investigated the effects of close-in explosive airblast loads on the downstream toe of a homogeneous earthen embankment dam composed of cohesive soils. Small-scale explosive airblast experiments were performed on cohesive soils to obtain an experimental data set with which to compare numerical analyses. Experimental measurements included crater geometry, ground vibration energy, and air overpressure from the blast events. Laboratory tests were conducted on the experiment soils to obtain engineering properties including shear strength and compressibility indices. Finite element simulations of airblast loading on a cohesive soil embankment dam were performed using Multi-Material Arbitrary Lagrangian Eulerian (MM-ALE) methods in LS-DYNA and compared to experimental results. Blast effects on varying reservoir levels and engineered drainage were investigated to determine the impact on dam stability. The airblast simulations created craters on the downstream slope and reduced the toe length. While larger explosive masses removed more material, crater dimensions did not significantly increase with explosive mass due to energy loss in air. Circular slip surfaces intersected the crater and reduced stability for dams with no engineered drainage. A horizontal toe drain effectively lowered the phreatic surface away from the blast crater and increased structural stability. Failure (as defined by a factor of safety less than unity) was induced in dams with no engineered drainage at reservoir levels of 80 percent reservoir capacity or greater. Dams with lower reservoir levels did not experience failure from an explosive airblast event. In addition, failure could not be induced in dams with engineered drainage. It was concluded that explosive airblasts posed a possibility of slope failure only for dams with no engineered drainage that were close to full reservoir capacity

Particulate Matter Reduction in Residual Biomass Combustion

Counteracting emissions of particulate matter (PM) is an increasingly important goal in sustainable biomass combustion. This work includes a novel approach to investigate the PM emissions, originating from residual biomass combustion, at different combustion conditions in a lab-scale grate-fired furnace and includes in situ PM measurements by using on-line sensors. The interior furnace design allows installation of baffles to suppress the emissions by controlling the residence time. Moreover, the two-thermocouple method is used to measure the true gas temperature, and an on-line spatially resolved PM measurement method is developed to study the evolution of the PM concentration throughout the furnace for different experimental conditions thereby allowing accurate in-situ measurement of the PM reactivity. Experimental results and computational fluid dynamics (CFD) analyses are utilized in the current work to develop a kinetic model for reduction of particulate matter emissions in biomass combustion. The discrete particle model (DPM) is utilized in CFD analysis to improve the understanding of the particle temperature and residence time distribution which are difficult to quantify experimentally. By combining the experimental measurements of real soot formed during biomass combustion and information from the CFD analyses, a predictive kinetic model for PM10 reduction in biomass combustion is successfully developed

A new fuzzy set merging technique using inclusion-based fuzzy clustering

This paper proposes a new method of merging parameterized fuzzy sets based on clustering in the parameters space, taking into account the degree of inclusion of each fuzzy set in the cluster prototypes. The merger method is applied to fuzzy rule base simplification by automatically replacing the fuzzy sets corresponding to a given cluster with that pertaining to cluster prototype. The feasibility and the performance of the proposed method are studied using an application in mobile robot navigation. The results indicate that the proposed merging and rule base simplification approach leads to good navigation performance in the application considered and to fuzzy models that are interpretable by experts. In this paper, we concentrate mainly on fuzzy systems with Gaussian membership functions, but the general approach can also be applied to other parameterized fuzzy sets

Resolving Spatial and Temporal Variability in Dissolved Organic Matter Characteristics within Combined Agricultural and Stormwater Conveyances

In many urban areas, stormwater runoff can threaten the ecological health of streams and downstream water bodies. Due to the increased impervious nature of urban landscapes, runoff is more “flashy” and as a result, high concentrations of pollutants can be transported in shorter periods of time than in more natural environments. One pollutant of concern is dissolved organic matter (DOM). DOM is important within aquatic ecosystems, but excess amounts can cause depletion in dissolved oxygen concentrations and can negatively affect aquatic organisms. This study investigated changes in DOM quantity and sources within the Northwest Field Canal (NWFC), an urban water conveyance located in Logan, Utah, USA that receives runoff during storm events. DOM was monitored at upstream and downstream locations within the canal and at selected stormwater outfalls within the study reach. During storm events, DOM concentrations were rapidly elevated to values orders of magnitude greater than in baseflow measurements, and were greater at the downstream site than at the upstream site, triggered by contributions from outfalls discharging into the canal. Changes in DOM composition during storm events confirmed that DOM is more terrestrially derived, whereas it is normally more microbially derived during baseflow conditions in the canal. These results provide better understanding of the composition of DOM in the canal system and may provide crucial information for future management of stormwater runoff that can potentially lead to the improvements of water quality in downstream water bodies

A quantitative analysis of stratospheric HCl, HNO3, and O3 in the tropopause region near the subtropical jet

The effects of chemical two-way mixing on the Extratropical Transition Layer (ExTL) near the subtropical jet are investigated by stratospheric tracer-tracer correlations. To this end, in situ measurements were performed west of Africa (25–32◦N) during the Transport and Composition of the Upper Troposphere Lower Stratosphere (UTLS)/Earth System Model Validation (TACTS/ESMVal) mission in August/September 2012. The Atmospheric chemical Ionization Mass Spectrometer sampling HCl and HNO3 was for the first time deployed on the new German High Altitude and Long range research aircraft (HALO). Measurements of O3, CO, European Centre for Medium-Range Weather Forecasts (ECMWF) analysis, and the tight correlation of the unambiguous tracer HCl to O3 and HNO3 in the lower stratosphere were used to quantify the stratospheric content of these species in the ExTL. With increasing distance from the tropopause, the stratospheric content increased from 10% to 100% with differing profiles for HNO3 and O3. Tropospheric fractions of 20% HNO3 and 40% O3 were detected up to a distance of 30 K above the tropopause

Stable Isotope Composition of Surface Vapour and Precipitation at the Southwest Coast of Norway

A better understanding of the water cycle has become even more crucial under the present condition of climate change. The stable isotopes of hydrogen and oxygen have been used for decades as powerful tracers to provide insights into the water cycle. While substantial understanding has been achieved, disputes remain on what processes set the observed isotope signal. Besides, albeit its great usefulness, no systematic isotope observations have existed in western Norway, which is a midlatitude location influenced by distinct weather systems (e.g. North Atlantic cyclones, cold air outbreaks) and swift precipitation formation. In this thesis, I present a systematic isotope observation of surface vapour and precipitation at the southwest coast of Norway between December 2016 and November 2019. The observation consists of high-resolution samplings for targeted weather events and long term (quasi-daily) routine samplings. To facilitate these observations, a stable water isotope laboratory with 3 laser spectrometers has been established. To ensure high-quality data acquisition, we thoroughly assess the instrument performance in many aspects. One important aspect is the correction of the mixing ratio dependency. In Paper I, we systematically investigate the mixing ratio dependency in a range from 500 to 23 000 ppmv. We find that the mixing ratio dependency systematically varies with the isotope composition of measured vapour. We refer this as isotope composition-mixing ratio dependency and have developed a scheme to correct for this dependency-introduced bias. Using in situ measurements from an aircraft measurement, we demonstrate the importance of the correction at low mixing ratios. Stability tests over up to 2 years indicate that the first-order dependency is a constant instrument characteristic that may be primarily related to spectroscopy. In Paper II, we present a case study of a 24-h land-falling "atmospheric river" event on 07 December 2016, with high-resolution paired measurements of near-surface vapour and precipitation stable isotopes. We observe a stretched, "W"-shaped evolution of isotope signals. Combining surface meteorological observations, we identify the influences on the isotopic signals from below-cloud processes, weather system characteristics, transport history, and moisture source conditions. We thus revisit the interpretations of previous studies on such precipitation events and emphasise that cloud microphysics and below-cloud processes are important factors influencing surface precipitation isotope signals. Paper III presents the 3-year paired observation of surface vapour and precipitation stable isotopes. The isotopic variation on different time scales is investigated. We observe a weak diurnal variation and a moderate seasonal variation. On the multi-day time scale, we observe a clear association between the isotope signals and the regional weather regimes. We also compare the d-excess observations with model predictions based on Lagrangian moisture source diagnostic and previously suggested d-RH SST relationships. We find that the models correctly reproduce the variation patterns, but with substantial offsets. While further investigations are required, our observations are of great importance for extending the sparse existing isotope observation network and enabling potential comparison with different models. In a combination of the three papers above, this work makes an important contribution to the interpretation of near-surface stable isotope observations on a range of time scales, from sub-hourly to synoptic, to inter-annual. It highlights the value of stable isotope observations for advancing our knowledge of the atmospheric hydrological processes.Doktorgradsavhandlin