¡Salvem es Trenc!

Abstract not availabl

Artificially generating sediment incipient motion in natural conditions

Incipient motion thresholds for gravel bed rivers are studied in flumes and natural rivers. Flume studies allow variables such as channel slope, water velocity, water depth, sediment size and sediment composition to be controlled. Meanwhile, in the field, the incipient motion of particles is studied in natural conditions allowing the structure of the bed and the flood characteristics to be considered. Though much less developed, an intermediate possibility also exists. By artificially accelerating near bottom velocity of the water flow in a small portion of the bed, it is possible to initiate sediment transport. This allows sediment incipient motion to be observed in natural conditions while controlling the water velocities. The Cemagref (HHLY) has developed a device which confines water flow in a small tunnel on the bottom of the riverbed. It was developed in order to create a boundary layer similar to the one generated by natural flow. Water is injected into a filter which smoothes the flow before it enters a Plexiglas tunnel where sediment motion is observed. The flow is accelerated by two large pumps that allow flow velocities of up to 2.5 m/s in a small area 40 cm long, 20 cm wide and 12 cm high. As the water flow is confined, large scale turbulence similar to that occurring in natural rivers cannot be reproduced using the device. The velocity profile in the tunnel is stable and in equilibrium with the riverbed. Sediment motion was observed using this device on three Belgian gravel bed rivers (3.5 cm <D50<8 cm). The incipient critical velocities measured were coherent in the three rivers sampled, ranging between 1.3 m/s and 1.7 m/s. A progressive increase in velocity in the tunnel permitted size selective entrainment to be observed. Analysis of the particle entrainment schemes and associated velocities allowed the role played by the armoured layer and the Di/D50 ratio to be more fully understood. Critical velocities measured using the device were also compared to critical velocities observed in natural conditions, determined during several pebble tracing campaigns. This revealed that incipient motion velocities of the largest particles recorded in artificial conditions were systematically larger than those observed in natural conditions. This demonstrates the roles played by large scale turbulence and the vertical component of the flow velocity in single particle entrainment. Due to its inherent characteristics, both of these flow components are weak in the artificial conditions generated by the device. In conclusion, our study demonstrates that this type of device is a useful tool in observing and studying incipient motion processes and, in particular, the role played by the bed structure (armouring, protrusion, etc.). However, some improvements are still required in order to more accurately measure critical velocities, allowing critical discharges to be determined

Menorca i el turisme. Contencions i atractius

Abstract not availabl

South Sudan community garden project : Manchester, New Hampshire, USA

The South Sudan Community garden project is a program designed for the South Sudanese refugees between ages 24 to 44 years old living in New Hampshire. The purpose of this project is to provide Sudanese refugees with gardening-related skills and resources ownership that will enable them to advance closer to self-employment and personal goals to give them an opportunity to become active participants in the social, political and economic richness of American life. The main purpose is to empower south Sudanese refugees with the ownership that they need to gain self employment and better economic opportunities in order to tackle poverty by increasing their household income. This project is implemented in partnership with the International Institute of New Hampshire (IINH) and South Sudanese Community Center (SSCC) at Manchester, NH, for an initial period of seven months. The mission of both (IINH) and (SSCC) is to provide the resources, land, and tools, access to trades in order to become economically self-sufficient. The International Institute NH's Agriculture has long history of helping refugees in farming. Based on their broad experiences in this field, the project benefitted from their partnership and support to the participants. (Author abstract)Gob, M. G. (2011). South Sudan community garden project Manchester, New Hampshire, USA. Retrieved from http://academicarchive.snhu.eduMaster of Science (M.S.)School of Community Economic Developmen

Modeling electrodialysis and a photochemical process for their integration in saline wastewater treatment.

Oxidation processes can be used to treat industrial wastewater containing non-biodegradable organic compounds. However, the presence of dissolved salts may inhibit or retard the treatment process. In this study, wastewater desalination by electrodialysis (ED) associated with an advanced oxidation process (photo-Fenton) was applied to an aqueous NaCl solution containing phenol. The influence of process variables on the demineralization factor was investigated for ED in pilot scale and a correlation was obtained between the phenol, salt and water fluxes with the driving force. The oxidation process was investigated in a laboratory batch reactor and a model based on artificial neural networks was developed by fitting the experimental data describing the reaction rate as a function of the input variables. With the experimental parameters of both processes, a dynamic model was developed for ED and a continuous model, using a plug flow reactor approach, for the oxidation process. Finally, the hybrid model simulation could validate different scenarios of the integrated system and can be used for process optimization

Quantifying the physical alterations of river reaches using a regional river morphology reference model. A step towards river restoration.

River engineeringRiver habitat management and restoratio

Introduction to the special issue in honor of Prof. François Petit

peer reviewe