A sharp height estimate for compact hypersurfaces with constant kk-mean curvature in warped product spaces

In this paper we obtain a sharp height estimate concerning compact hypersurfaces immersed into warped product spaces with some constant higher order mean curvature, and whose boundary is contained into a slice. We apply these results to draw topological conclusions at the end of the paper.Comment: 19 pages. To appear on Proceedings of the Edinburgh Mathematical Societ

Analysis of fouling resistances under dynamic filtration of pretreated olive mill wastewater on a loose reverse osmosis membrane

In this work, a loose reverse osmosis (RO) membrane (Osmonics AK model), capable of offering beforehand higher fluxes under lower operating pressure than typical tight reverse osmosis membranes but still offering similar rejection, was used for the final purification of olive mill wastewater. However, the output that a membrane may offer when it is virgin and readily used will change in time due to membrane fouling. If not properly considered, the advantages that a chosen membrane may offer in contrast with others would quickly and often irreversibly vanish, with the consequences in terms of capital expenses that this will represent. One approach to meet the investor's needs to trust membrane technology is to guarantee that fouling will be inhibited as much as possible, but to overcome the loss of performance that fouling carries engineers overdesign the membrane plants by using too wide safety margins that trigger the costs sensibly. Since the mechanisms by which fouling phenomena are triggered are always complex, the osmotic-pressure resistances-in-series model can be a simple but reliable model to describe the membrane response and predict its performance in time. In this context, the normalized fouling measured on the examined RO membrane was found to be minimum in the operating pressure range between 5 and 8 bar (0.65-0.98, respectively), and it decreased down to 0.51 upon increasing the crossflow up to 5.09 m s-1, avoiding irreversible fouling. Moreover, significantly minor fouling (0.33) was attained at the lowest temperature, regularly experienced during the olive oil production campaign. On another hand, the rejection towards organic solutes was maintained above 97%

Optimization study of the fouling build-up on a RO membrane for pretrated olive mill wastewater purification

Even though membranes are considered in many aspects a mature technology, a range of features are still in development and under investigation. Regarding this, the main handicap of this technology is inevitably membrane fouling. Fouling issues have investigated by many research groups in the last years to convince investors to implement membranes as substitutes of a range of unit operations at industrial scale. In the wastewater treatment field, this is especially problematic, given the low economic value of the product, that is, treated water. On another hand, the management of the effluents generated by olive oil industries, olive mill wastewaters (OMW), is a task of global concern not anymore constrained to a specific region. These wastewaters represent an ever-increasing problem still unresolved. The present work was aimed for the modelling and optimization of a reverse osmosis (RO) membrane operation for the purification of pretreated olive mill wastewater, with a focus on the dynamic fouling development minimization on the selected membrane as a function of the set-up of the operating conditions. For this goal, beforehand a factorial design was implemented for the optimization of the RO treatment of the OMW stream. The results gathered were thereafter interpreted by means of the response surface methodology. A significant impact was noted to be driven by the operating pressure and the tangential velocity on the fouling rate on the RO membrane. The response surfaces withdrawn from the experimental data support the previous results, and the optimised parameters - ambient temperature range (24 - 25 °C), moderate operating pressure (25 - 30 bar) and turbulent tangential flow (3.1 - 3.5 m s -1 ) - were found to provide a stable permeate flux of 32.3 - 38.5 L h -1 m -2 . These results reveal the proposed process could be operated successfully at ambient temperature conditions and medium operating pressure, boosting the economic efficiency of the RO purification of this effluent. Finally, the parametric quality standards stablished to reuse the purified effluent for irrigation purposes were checked and found to be satisfactory

A focus on fouling of nanofiltration membranes in the treatment of two-phase olive mill wastewater by boundary flux and pore blocking theories

The implementation of membranes in water and wastewater treatment processes has significantly increased in the last decades. However, membrane fouling leads to increased expenses if not properly examined and considered, and this is especially problematic in wastewater treatments. For this reason, fouling minimization represents the key factor to make those processes feasible. The use of NF membranes is especially problematic regarding fouling problems. In first place, adequate fouling inhibition methods should be designed upstream the membrane operation, in order to make the downstream membrane processes for wastewater treatment technically and economically feasible. In the present work, fouling build-up on a nanofiltration (NF) membrane during the treatment of olive mill wastewater coming from Spain (OMW-S) is addressed by the boundary flux theory, and the results were compared and complemented by using the pore blocking models. Fouling mechanisms are important to fully understand what is happening between the membrane and the effluent, to take the adequate decisions with respect to the design of the membrane plant and set-up of optimized operating conditions. The goal is to operate membranes modules by avoiding irreversible fouling for a long period of time, that is, several years of service lifetime. Thereafter, the operating parameters should be carefully chosen to avoid working beyond the conditions that the selected membrane can stand for the specific feedstream. The followed strategy allows the operation of the membranes system in a controlled framework that permits the stable operation of the plant. Moreover, the required membrane area is minimized and the constancy of the permeate productivity is also narrowed by following the proposed methodology

Improved electromagnetic compatibility standards for the interconnected wireless world

© 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.The future is wireless, a world where everything is interconnected. However, the current standards for ensuring the electromagnetic compatibility (EMC) and the coexistence of such wireless systems urge for a major update. It is shown how novel statistical approaches based on the amplitude probability distribution detector and time-domain measurements are better suited for estimating the degradation caused by electromagnetic interferences on digital communication systems than the established practice of determining compliance according to the quasi-peak detector levels using a pass/fail criterion. Therefore, a redefinition of the test methods and of the compliance requirements in terms of EMC standards must be a priority of the international standardization bodies. Finally, a discussion of the fundamental challenges involved in this standardization breakthrough for EMC is delivered.Postprint (author's final draft

Benefits of full time-domain EMI measurements for large fixed installation

It is difficult to properly evaluate the electromagnetic disturbances generated by large fixed installations because of, i.e., the background noise, unsteady emissions and transient interferences. Those challenging EMC issues have been recently studied in European research projects on improved test methods in industrial environments. In order to overcome traditional in-situ EMI measurement troubles, a novel time-domain methodology is proposed and used in a real fixed installation with large machinery. Firstly, a comparison between the developed measurement system, using an oscilloscope, and an EMI receiver is done in some test-cases for validation purposes. After verifying the accuracy of the measurements, we proceed with the measurement campaign applying the full time-domain methodology. The main benefits of employing the time-domain system are emphasised through the results. It was observed that the some remarkable advantages of the time-domain approach are: triggering by disturbance events, extremely reduce the capturing time, identify on real time the worst emissions modes of the EUT, avoid changes at the background noise and perform simultaneous multichannel synchronous measurements.Postprint (published version