Impatti, adattamento e vulnerabilita Le cause e le responsabilita dei cambiamenti climatici sono state trattate sul numero di ottobre della rivista Cda. Approfondiamo l’argomento presentando il documento: “Cambiamenti climatici 2007: impatti, adattamento e vulnerabilita” votato ad aprile 2007 dal secondo gruppo di lavoro del Comitato Intergovernativo sui Cambiamenti Climatici (Intergovernmental Panel on Climate Change). Si tratta del secondo di tre documenti che compongono il quarto rapporto sui cambiamenti climatici.

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Climate Change 2007: Impacts, Adaptation and Vulnerability.

The use of unmanned aerial vehicles (UAVs) is growing rapidly across many civil application domains, including real-time monitoring, providing wireless coverage, remote sensing, search and rescue, delivery of goods, security and surveillance, precision agriculture, and civil infrastructure inspection. Smart UAVs are the next big revolution in the UAV technology promising to provide new opportunities in different applications, especially in civil infrastructure in terms of reduced risks and lower cost. Civil infrastructure is expected to dominate more than $45 Billion market value of UAV usage. In this paper, we present UAV civil applications and their challenges. We also discuss the current research trends and provide future insights for potential UAV uses. Furthermore, we present the key challenges for UAV civil applications, including charging challenges, collision avoidance and swarming challenges, and networking and security-related challenges. Based on our review of the recent literature, we discuss open research challenges and draw high-level insights on how these challenges might be approached.

Unmanned Aerial Vehicles: A Survey on Civil Applications and Key Research Challenges

In-service structural health monitoring (SHM) of engineering structures has assumed a significant role in assessing their safety and integrity. Fibre Bragg grating (FBG) sensors have emerged as a reliable, in situ, non-destructive tool for monitoring, diagnostics and control in civil structures. The versatility of FBG sensors represents a key advantage over other technologies in the structural sensing field. In this article, the recent research and development activities in structural health monitoring using FBG sensors have been critically reviewed, highlighting the areas where further work is needed. A few packaging schemes for FBG strain sensors are also discussed. Finally a few limitations and market barriers associated with the use of these sensors have been addressed.

Fibre Bragg gratings in structural health monitoring—Present status and applications

High resolution schemes for hyperbolic conservation laws

By trapping sediment in reservoirs, dams interrupt the continuity of sediment transport through rivers, resulting in loss of reservoir storage and reduced usable life, and depriving downstream reaches of sediments essential for channel form and aquatic habitats. With the acceleration of new dam construction globally, these impacts are increasingly widespread. There are proven techniques to pass sediment through or around reservoirs, to preserve reservoir capacity and to minimize downstream impacts, but they are not applied in many situations where they would be effective. This paper summarizes collective experience from five continents in managing reservoir sediments and mitigating downstream sediment starvation. Where geometry is favorable it is often possible to bypass sediment around the reservoir, which avoids reservoir sedimentation and supplies sediment to downstream reaches with rates and timing similar to pre-dam conditions. Sluicing (or drawdown routing) permits sediment to be transported through the reservoir rapidly to avoid sedimentation during high flows; it requires relatively large capacity outlets. Drawdown flushing involves scouring and re-suspending sediment deposited in the reservoir and transporting it downstream through low-level gates in the dam; it works best in narrow reservoirs with steep longitudinal gradients and with flow velocities maintained above the threshold to transport sediment. Turbidity currents can often be vented through the dam, with the advantage that the reservoir need not be drawn down to pass sediment. In planning dams, we recommend that these sediment management approaches be utilized where possible to sustain reservoir capacity and minimize environmental impacts of dams.

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Sustainable sediment management in reservoirs and regulated rivers: Experiences from five continents

The paper presents a two‐dimensional unsteady‐flow model, RBFVM‐2D, based on the finite‐volume method with a combination of unstructured triangular and quadrilateral grids in a river‐basin system. The attractive feature of this model is that it calculate of the mass and momentum flux across each side of elements as a Riemann problem, which is solved using the Osher scheme. This feature enables this model to deal with the wetting and drying processes for flood‐plain and wetland studies, dam breaking phenomena involving discontinuous flows, subcritical and supercritical flows, and other cases. The computations of tributary inflows and regulated flows through gates, weirs, and culverts or bridges are also included. Sample applications of this model to two dam‐break problems showed fairly satisfactory results. Also, this model was applied to a portion of the Kissimmee River Basin in Florida for flow simulations and the results agreed well with the field and laboratory data in a physical‐model study of this ri...

Finite‐Volume Two‐Dimensional Unsteady‐Flow Model for River Basins

Civil engineers always face the challenge of uncertainty in planning, building, and maintaining infrastructure. These works rely heavily on a variety of surveying and monitoring techniques. Unmanned aerial vehicles (UAVs) are an effective approach to obtain information from an additional view, and potentially bring significant benefits to civil engineering. This paper gives an overview of the state of UAV developments and their possible applications in civil engineering. The paper begins with an introduction to
UAV hardware, software, and control methodologies. It also reviews the latest developments in technologies
related to UAVs, such as control theories, navigation methods, and image processing. Finally, the paper
concludes with a summary of the potential applications of UAV to seismic risk assessment, transportation,
disaster response, construction management, surveying and mapping, and flood monitoring and assessment.

A review of rotorcraft Unmanned Aerial Vehicle (UAV) developments and applications in civil engineering

This paper presents three approximate Riemann solver schemes, namely: the flux vector splitting (FVS), the flux difference splitting (FDS), and the Osher scheme. Originally used to solve the Euler equations in aerodynamic problems, these Riemann solvers based on the characteristic theory are used in the finite volume method (FVM) for solving the two-dimensional shallow water equations. The three solvers are compared in this paper according to theoretical development, difference schemes, practical applications to shock wave problems, and sensitivity analysis on the computational stability of the methods. The effects of changes in bed elevations on the solutions are also investigated. Comparison of numerical and analytical solutions indicates that very good agreement can be obtained by all three approximate Riemann solvers. Differences in accuracy, computer time, and numerical stability among the three schemes are not significant. For practical purposes, all of them can satisfactorily simulate the hydraulic phenomena in subcritical and supercritical flows as well as in smooth and discontinuous flows, especially shock wave modeling. These solvers are useful for studying levee failure or dam break due to extreme flood events, or the sudden opening or closing of sluice gates in a channel.

Approximate Riemann solvers in FVM for 2D hydraulic shock wave modeling

The control of reservoir sedimentation through hydraulic flushing has been employed in several parts of the world to sustain the useful storage capacity of the reservoirs. However, no comprehensive analysis has been conducted to understand the sediment flushing processes. In this study, laboratory experiments were performed to investigate the flushing processes during drawdown flushing, including outflow sediment discharge, characteristics of the flushing channel and flushing effectiveness. From both laboratory and field data, it is found that outflow sediment discharge can be well related to a hydrauic parameter which is a function of outlet discharge, water-surface gradient and flushing channel width. It is also found that flushing efficiency increases dramatically when retrogressive erosion emerges. A geomorphic relationship is used to estimate the equilibrium width of the flushing channel. A 1-D diffusion model presented herein is employed only to simulate the general trend of bed profile evolution an...

Flushing sediment through reservoirs

Experiments of bridge pier scour are carried out under steady and unsteady clear-water scour conditions with uniform and nonuniform sediments. Around the pier nose, the sediment size variation of surface bed materials is investigated, and a regressed formula is obtained for estimating the mixing layer thickness in terms of median sediment size and geometric standard deviation of grain size distribution. A method based on the mixing layer concept is developed for calculating the equilibrium scour depth in nonuniform sediment. Based on the experimental data of scour rate, a model simulating the scour-depth evolution under steady flow in nonuniform sediment is presented. By analyzing experimental data, a scheme is proposed for computing the scour-depth evolution under unsteady flow.

Jihn-Sung Lai

Papers

Finite‐Volume Two‐Dimensional Unsteady‐Flow Model for River Basins

A review of rotorcraft Unmanned Aerial Vehicle (UAV) developments and applications in civil engineering

Approximate Riemann solvers in FVM for 2D hydraulic shock wave modeling

Flushing sediment through reservoirs

Evolution of Scour Depth at Circular Bridge Piers