1,721,036 research outputs found
Flow regimes on stepped spillways
No full textThe recent improvements of the construction techniques and the particular attention to the environment have renewed the interest in stepped spillways. New experimental investigations have been carried out at the Technical University of Bari, extending the available data on the hydraulic behaviour. The classification of flow regimes has been re-analysed, taking into account the mathematical relationships derived from the technical literature. The study confirms the difficulties in understanding the problem and points out the need for standard experimental procedures, for refining the hydraulic comprehension of the problem
A comparison between phragmites australis and helianthus annuus in chromium phytoextraction
No full textA comparison of chromium abatement from irrigation water, by the use of two selected plant species, Phragmites australis and Helianthus annuus, planted in chromium-contaminated soil, was studied in the present work. The above plant species were irrigated, in a continuous mode, with 10 mg Cr-VI/L contaminated tap water. More than 90 % of hexavalent chromium was reduced to trivalent chromium, from both plant species, as measured in the drainage water. Moreover, total chromium removal ranged from 54 % (Phragmites) to 70 % (Helianthus). After 90 days, the total chromium content of the contaminated soil dropped from 70 to 32 and 34 mg Cr/kgdry soil, for Helianthus and Phragmites, respectively. Helianthus accumulated higher amount of chromium in the roots (2,730 mg Cr/kg(dry tissue)) as compared to 1,800 mg Cr/kg(dry tissue) for Phragmites. Most of Cr-VI was reduced to Cr-III in all plant tissues, with Phragmites showing lower affinity for Cr-VI reduction in the root tissues but higher chromium translocation potential from roots to stems, while Helianthus showed higher chromium translocation from roots to leaves. Toxicity effects, expressed as root growth rate inhibition, indicated that Phragmites were the most tolerant specie to chromium effects. Both plant species showed high potentialities to be used in phytoremediation installations for chromium removal
Dissipation efficiency of stepped spillways
No full textThis study on hydraulic structures used for dissipating energy downstream from dams offers interesting suggestions for applied research aiming to improve hydraulic efficiency and constrain construction costs without neglecting environmental aspects.
Extensive experimental tests have been carried out in the laboratory of Dipartimento di Ingegneria delle Acque at Bari Polytechnic. Three different geometric configurations were analysed, each characterised by a constant step number and step height, but with different chute slopes. The experimental study focused on two aspects of physical interpretation of the phenomenon: the first concerned with the definition of the flow conditions, as defined by the device geometry and the flow dynamics, and the second with the evaluation of the rate of energy dissipation. The results seem to confirm the notorious difficulties in understanding the problem, even if the experimental data show the same trend as those obtained by other researchers
A spatial and temporal analysis for long term renewal of water pipes
No full textDrinking Water distribution systems as well as other technical networks represent an important accounting capital. Water networks are an assembly of technical devices, most of them are buried. This makes their diagnosis more difficult and requires the implementation of a policy, known by «asset management. This requires planned actions in the short, medium and long term. It aims to describe the state of the asset by developing specific tools in a first time and plan the actions needed to maintain its state in a second phase. The current research deals with the problematic of pipes prioritisation for rehabilitation. The developed approach is based on the discrimination of pipes by a spatial and temporal analysis starting from a simple idea: the diagnosis is often unaware dimensions: topology and evolution of failures pattern. Thus, detailed approach provides a holistic vision of the network by identifying areas with high failures, called "hotspots" and their evolution over time. Therefore, this research allows a visual representation using the network topology; such representation provides a resolution of the network and can be used to evaluate, a priori, the effectiveness of the rehabilitation policies according to their incidence on hotspots' decrease
Detection of spatio-temporal changes of vegetation in coastal areas subjected to soil erosion issue
Full text linkCoastal soil erosion can be recognized as the most alarming environmental issue since, causing shoreline retreat, reduces the area available for plant habitat survival, highly influencing their health status, and, consequently, limiting their ability in beach front properties protection. A deep knowledge of vegetation changes is required to identify the proper strategy to be adopted to face soil erosion problems in coastal areas. Therefore, the current paper is aimed to quantitatively examine the spatio-temporal changes suffered by the vegetation in the coastline of Siponto in Apulia Region (Southern Italy) covering a time period of about forty years. LANDSAT images from 1975, 2006, 2011 and 2018 were collected, atmospherically corrected and, finally, processed to generate binary classification maps of vegetation by applying the Composite Vegetation Index, a novel index based on the interpolation of Red, Green and Near-Infrared bands, suitable for catching both cellular and metabolic features of vegetation. Then, the generated binary classification maps were compared using the Vegetation Index Differencing technique, a post-classification change detection technique. The results showed an increase in vegetation extension cover and density overall the entire examined period. That phenomenon appeared more and more prominent between 1975 and 2006, where an increment of vegetated areas extension of about 88% were registered. Combining of the novel vegetation index, developed ad-hoc in the current research, and Vegetation Index Differencing approach shows promising results in vegetation classification and comparison over the time. Indeed, the method allows the fast vegetation extraction, great processing time saver. Nevertheless, spatial resolution of Landsat Images limits the classification of small and low-density vegetated areas. Therefore, future work should plan to test the proposed approach at a more detailed scale
Monitoring and modelling the erosion processes on the hillslopes of the Rendina lake
No full textThe morphological evolution of the landscape and the relating instability processes and soil transport phenomena in Southern Italy are the result of weathering and water erosion processes. The paper presents the preliminary results of an ongoing multidisciplinary research aiming at the assessment of the different types of erosion forms developing in different soil formations which are responsible for significant soil losses. As well, the research objective is the understanding of the sequence of processes producing the observed erosion phenomena and, in the long term, the proposal of rational measures able to mitigate erosion and the consequent transport and sedimentation processes. In order to achieve these objectives, the research is developed, on one side, through both in-situ and laboratory phenomenological analyses of the soil characteristics and water erosion processes; on the other side, through numerical analysis of the phenomena, implementing both the in-situ and the laboratory observations
Improving Operation of Pressurized Irrigation Systems by an Off-grid Control Devices Network
No full textWater demand in irrigation is expected to increase in the near future, and it will be seriously impacted by climate change, specifically in semi-arid areas. The increase of water demand, along with the reduction of water availability, can seriously intensify the frequency and magnitude of pressure deficits in pressurized irrigation networks, with dangerous consequences on the healthy crop growth and on the crop production. In this framework, the present paper investigates the contribution of a network of smart control valves, named GreenValve System (GVS, patented by the Politecnico di Milano), to improve the management of a pressurized irrigation system. The GVS is able to recover energy for its operation from the flow, to be remotely commanded and to introduce management logics based on real-time data in order to create a stand-alone real-time monitoring and control network. In the paper, specifically, a three-step general and replicable methodological approach for the definition of installation and operating conditions for these valves is proposed. The effectiveness of a specific management logic, allowed by the use of the GVS, to limit pressure deficit and failure occurrence in the network is discussed. Reference is made to a case study on a critical on-demand irrigation network. The results showed that the introduction of simple management rules can reduce and even avoid the occurrence of hydrant failure, creating the conditions for more effective use of the resources
- …
