The Cost of Irrigation Water Delivery: An Attempt to Reconcile the Concepts of Cost and Efficiency

This work discusses the conflict between two of the main objectives of the EU Water Framework Directive: cost recovery and economic efficiency in the use of irrigation water. In the Mediterranean region, this conflict is commonly embedded in a state of under-utilization of irrigation networks managed by Water User Associations (WUAs). This under-utilization arises from factors independent of farmers’ choice, such as water shortage, crises in the sector, and changes to the Common Agricultural Policy. This prevents the facilities from operating at the minimum average cost. This paper argues that farmers should not suffer this inefficiency, which results in them paying higher water prices to cover the costs of water supply. Indeed, the application of the Water Directive should be rethought, taking into account the specific problems related to irrigation in the Mediterranean region. Based on an econometric analysis of the costs of water distribution in a WUA in Sardinia (Italy), we propose a payment system based on two components. Primarily there is a fee related to the number of hectares under irrigation. In addition there is a fee that considers the intensity of irrigation: this component is to encourage farmers to save water. The results show that the proposed approach has some desirable effects, including higher rates of cost recovery and possibly a reduction in the use of groundwater. Finally, the proposed system is not overly expensive for the rest of the community, who must bear the costs of inefficiencies in the use of irrigation water that do not depend on choices of farmers.     

Spatial resolution enhancement of ultrasound images using neural networks

Spatial resolution in modern ultrasound imaging systems is limited by the high cost of large aperture transducer arrays, which require a large number of transducer elements and electronic channels. A new technique to enhance the spatial resolution of pulse-echo imaging systems is presented. The method attempts to build an image that could be obtained with a transducer array aperture larger than that physically available. We consider two images of the same object obtained with two different apertures, the full aperture and a subaperture, of the same transducer. A suitable artificial neural network (ANN) is trained to reproduce the relationship between the image obtained with the transducer full aperture and the image obtained with a subaperture. The inputs of the neural network are portions of the image obtained with the subaperture (low resolution image), and the target outputs are the corresponding portions of the image produced by the full aperture (high resolution image). After the network is trained, it can produce images with almost the same resolution of the full aperture transducer, but using a reduced number of real transducer elements. All computations are carried out on envelope-detected decimated images; for this reason, the computational cost is low and the method is suitable for real-time applications. The proposed method was applied to experimental data obtained with the ultrasound synthetic aperture focusing technique (SAFT), giving quite promising results. Realtime implementation on a modern, full-digital echographic system is currently being developed.     

On the Electron Transient Response in a 50 nm MOSFET by Ensemble Monte Carlo Simulation in Presence of the Smoothed Potential Algorithm

The inclusion of a smoothed potential algorithm within the Ensemble Monte Carlo method (EMC) to account for quantization effects in the inversion layer of a silicon n-MOSFET has been discussed by several authors. Most of the data reported deal with steady state terminal current, transconductance, and capacitance. Within this approach, the electric field acting on each particle is computed from the smoothed potential, which introduces a potential barrier underneath the gate region that pushes the carriers away from the interface, thus accounting for space quantization effects. However, in the EMC method, the electric field at the interface is also used to compute the displacement charge/current during the transient regime. In the implementation of the smoothed potential algorithm, care must be taken when computing this component of the total gate charge. We distinguish between two differently computed electric fields, one from the smoothed potential used for the charge transport and the other one computed from the real potential, as obtained from the solution of Poisson's equation, and used for the displacement charge. We propose this procedure in order to properly include space quantization effects, and at the same time avoid the inaccuracy introduced by the smoothed potential in the displacement charge.     

Studies of a thermomechanically treated Al-Zn-Mg alloy

The influence of subgrain structure on the precipitation process in an Al-4.2 wt% Zn-1.6 wt% Mg alloy was studied and correlated with its mechanical properties for ageing temperatures of 110, 142 and 165° C.     

Abiotic transformation of toxaphene by superreduced vitamin B12 and dicyanocobinamide

Toxaphene is a complex organochlorine pesticide mixture, residues of which are widespread in the environment. Previous studies with the isolated bacterium Sulfurospirillum (formerly Dehalospirillum) multivorans resulted in an effective anaerobic biotransformation of toxaphene. Since the bacterium contains a corrinoid derivative in the active center of the tetrachloroethene dehalogenase, we attempted to use superreduced corrinoids for abiotic transformation of toxaphene. The two corrinoids studied were dicyanocobinamide and cyanocobalamin (vitamin B12). Superreduced dicyanocobinamide mediated a rapid transformation of toxaphene. More than 90% of the initial pool was transformed within 6 h. The transformation was nonselective, and even the most persistent metabolite in environmental samples, the so-called dead-end metabolite 2-exo,3-endo,6-exo,8,9,10-hexachlorobornane (B6-923 or Hx-Sed) was transformed within hours. Superreduced cyanocobalamin was also able to transform toxaphene albeit at significantly lower velocity. The lack of transformation products detectable in gas chromatograms of hexanes-extracted fractions of the assays suggests rapid, sequential dehalogenation and/or destruction of the C10-hydrocarbon backbone of the compounds of technical toxaphene.     

Comparison of methods for determination of microbial biomass in wastewater

Microbial biomass in wastewater was determined by methods used in environmental microbiology and by a method used in wastewater engineering based on a conceptual model simulating fundamental microbial processes in wastewater from measured oxygen uptake rates. The methods originating from environmental microbiology are based on staining and counting of cells for the determination of total cell biomass (acridine orange and DAPI), physiological state of cells (LIVE/DEAD BacLight) and activity of cells (reduction of the redox dye CTC and microautoradiography). Depending on the staining method applied, cell biomasses yielded 15-86% of the biomass defined by the model, and good correlations between cell biomass and model biomass were found. Cell biomass, oxygen uptake and acetate uptake were measured in wastewater, where acetate was added. Substrate uptake rates were found not to be proportional to the increases in cell biomass, suggesting that only a small fraction of the cell biomass was responsible for the main part of the substrate uptake. Despite the differences found between cell biomass and model biomass, it was recommended to use the conceptual model as an engineering tool for simulation of microbial processes and wastewater quality changes. However, there should be a clear distinction between the terms 'model biomass', 'cell biomass' and different activity measurements of cells.     

Method of Calculating the Charge Acceptance of Organic Photoconductors

The charge acceptance of organic photoconductors (OPC) consisting of thin layers must attain the correct value in order to produce constant copy quality. In practice, however, it can be kept constant only by taking elaborate precautions, since a number of parameters have an adverse effect on charge acceptance. The limits are described within which the photoconductors and corona properties fluctuate in actual running machines. The properties of the photo-conductor can scarcely be influenced by the user, but proper choice of the electric parameters of the charging scorotron can largely suppress the influence of the fluctuations on the final charge of the photo-conductor. If the charging device exhibits the behavior of an ideal constant voltage supply characteristic, charge acceptance would depend solely on the tolerances of this device. If the charging device supplies constant current, charge acceptance depends primarily on the properties of the photoconductor. A careful estimate must be made to determine, under conditions as practical as possible, reasons for variations in charge acceptance. There are those caused by fluctuations in the charging device and those caused by fluctuations in the photoconductor. A mathematical method is described which makes it relatively simple to determine the actual OPC charge acceptance depending on application and variation of the electrical parameters.     

Oxidation Catalysts Based on Antimony Mixed Oxides with Rutile-Type Structures

Several authors have correlated catalyst structure to catalytic behavior in selective oxidation reactions. Sleight [1] reviewed the importance of the scheelite structure for the allylic oxidation and ammonoxidation of olefins; Grasselli and co-workers [2–4] extensively examined the relationship between structure and catalytic activity of bismuth-molybdates, uranium-antirnonates, and bismuth-cerium molybdates. Bordes and Courtine [5] correlated the activity in mild oxidation of 1-butene to the properties of the structure of vanadium-phosphorus oxides. However, little attention has been given in the literature to the role of the rutile structure in allylic oxidation reactions even though the high activity and selectivity of antimony oxides stabilized in matrices with rutile structure (SnO₂ and FeSbO₄) in olefins oxidation and ammonoxidation have been known for several years. Furthermore, Tables 1 and 2 indicate that the kinetic and catalytic behavior of antimony-based catalysts in allylic oxidation reactions are very different from that of molybdate-based catalysts. This suggests that antimony- and molybdate-based catalysts are two distinct classes of catalysts of allylic oxidation, in agreement with a recent suggestion by Grasselli et al. [13].