Determination of the solubility parameter of poly(ethylene oxide) at 25°C by gas-liquid chromatography

The solubility parameter of poly(ethylene oxide) at 25°C has been determined using the method developed by DiPaola-Baranyi and Guillet, by the extrapolation of the values of the interaction parameter χ, at high temperatures, ranging from 70°–90°, 90°–110° and 110°–130°C down to 25°C. The values of the solubility parameter obtained, depending on the temperature ranges employed, are 9.8, 9.9 and 10.1, respectively.     

OPTIMAL DESIGN AND PERFORMANCE OF SPIRAL WOUND MODULES I: NUMERICAL METHOD

A numerical method has been developed for the performance prediction of spiral wound modules with constant and tapered permeate spacers, It takes into account the pressure drop in the brine and permeate channels and makes use of a three parameter model for the mass transfer through the membrane. For a given application and operating conditions, optimum geometrical characteristics of modules can be found. Tapering the permeate spacer the specific permeation rate can be increased by 10-30%, the wider the membrane the higher the value.     

Online FPS games: effect of router buffer and multiplexing techniques on subjective quality estimators

First Person Shooters are a genre of online games in which users demand a high interactivity, because the actions and the movements are very fast. They usually generate high rates of small packets which have to be delivered to the server within a deadline. When the traffic of a number of players shares the same link, these flows can be aggregated in order to save bandwidth. Certain multiplexing techniques are able to merge a number of packets, in a similar way to voice trunking, creating a bundle which is transmitted using a tunnel. In addition, the headers of the original packets can be compressed by means of standard algorithms. The characteristics of the buffers of the routers which deliver these bundled packets may have a strong influence on the network impairments (mainly delay, jitter and packet loss) which determine the quality of the game. A subjective quality estimator has been used in order to study the mutual influence of the buffer and multiplexing techniques. Taking into account that there exist buffers which size is measured in terms of bytes, and others measured in packets, both kinds of buffers have been tested, using different sizes. Traces from real game parties have been merged in order to obtain the traffic of 20 simultaneous players sharing the same Internet access. The delay and jitter produced by the buffer of the access router have been obtained using simulations. In general, the quality is expected to be reduced as the background traffic grows, but the results show an anomalous region in which the quality rises with the background traffic amount. Small buffers present better subjective quality results than bigger ones. When the total traffic amount gets above the available bandwidth, the buffers measured in bytes add to the packets a fixed delay, which grows with buffer size. They present a jitter peak when the offered traffic is roughly the link capacity. On the other hand, buffers which size is measured in packets add a smaller delay, but they increase packet loss for gaming traffic. The obtained results illustrate the need of knowing the characteristics of the buffer in order to make the correct decision about traffic multiplexing. As a conclusion, it would be interesting for game developers to identify the behaviour of the router buffer so as to adapt the traffic to it.     

Laser-generated liquid microjets: correlation between bubble dynamics and liquid ejection

Laser-based techniques provide excellent means for liquid microprinting, with several advantages over other more conventional printing techniques, such as being nozzle-free (as opposed to inkjet, for instance) or requiring minimal engineering of the liquid properties in the pre-printing stage. In such techniques, the transfer is usually mediated by liquid jets that contact a receiver substrate placed nearby the liquid source, leading to the deposition of a small droplet. The main cause of jetting lies in a laser-generated bubble produced inside the liquid, whose dynamics dictates the evolution of liquid ejection. However, the detailed relationship between the bubble and the jet is not completely understood, as the studies carried out so far have been mostly focused on the jetting dynamics taking place above the liquid free-surface, without access to the liquid interior and therefore to the behavior of the bubble. In this work, we analyze through time-resolved imaging the film-free laser printing of an aqueous solution by simultaneously visualizing both the bubble evolution and the liquid ejection dynamics, thus making possible the correlation between the two phenomena. We find that the pulsating behavior of the bubble leads to successive jetting events with different jet morphologies arising from the particular geometries that the bubble acquires during its evolution. Finally, we find good agreement between our results and those from studies analyzing the dynamics of cavitation bubbles near the free-surface of a liquid through numerical solution of the fluid dynamics equations.     

Lipolytic and oxidative changes in 'Chorizo' during ripening

Changes in fats during the ripening of 'chorizo'-a Spanish dry sausage- elaborated by traditional and industrial processes have been studied. Total free fatty acids (FFA), carbonyls, volatile fatty acids (acetic acid), TBA number and individual FFA were determined. A marked increase of total free fatty acids was observed, although an increase of rancidity was not detected. Except in one of the batches studied in which a rise in carbonyls was reported, these compounds remained unchanged during the ripening in the rest of the batches analysed. No significant change occurred in the proportions of different free fatty acids during ripening in both types of 'chorizo'. There was a marked increase of acetic acid during the first days of ripening followed by a slow fall in the ultimate stages.     

Thermodynamic properties of ni nitrides and phase stability in the Ni-N system

The thermodynamics of the Ni-N system is poorly known from experiments, and there is a need of information on the stability of the various nitride phases and the Ni-N phase diagram. This kind of information has been obtained by us, by combining the few measurements available with predictions, based on recently reported regularities in bonding properties and vibrational entropy of 3d transition metal compounds. A calculated Ni-N phase diagram is presented. A certain range of homogeneity for the hexagonal nitride phase is obtained, which is comparable to that of other 3d transition metal-nitrogen systems. The question of the possible existence of a stable Ni₄N phase is examined. According to our results, Ni₄N is metastable in the Ni-N system.     

Online identification of appliances from power consumption data collected by smart meters

The efficient use of resources is a matter of great concern in today’s society, especially in the energy sector. Although the main strategy to decrease energy use has long been focused on supply, over the last few years, there has been a shift to the demand side. Under this new line of action, demand-side management networks have emerged and extended from the household level to larger installations, with the appearance of the concepts of Smart Grids and even Smart Cities. The extended use of Smart Meters for measuring residential electricity consumption facilitates the creation of such intelligent environments. In this context, this article proposes a system which extracts value from the collected consumer information to identify the appliances belonging to that smart environment by means of machine learning techniques. Considering the large amount of information that would be handled when millions of homes were sending data, big data technology has been used. An experiment to evaluate the classification method was carried out with seven devices and three different configurations. The results are also reported, achieving promising results, with recognition rates of 75 % after 1 h of training and 100 % after 4 h.