Influence of the Polarity of the Electric Field on Electrorheometry

Uniaxial extensional flow is a canonical flow typically used in rheological characterization to provide complementary information to that obtained by imposing simple shear flow. In spite of the importance of having a full rheological characterization of complex fluids, publications on the rheological characterization of mobile liquids under extensional flow have increased significantly only in the last 20 years. In the case of the rheological characterization of electrorheological fluids, the situation is even more dramatic, as the ERFs have been exclusively determined under simple shear flow, where an electrorheological cell is attached to the rotational rheometer generating an electric field perpendicular to the flow direction and that does not allow for inverting the polarity. The very recent work published by Sadek et al., who developed a new electrorheological cell to be used with the commercial Capillary Breakup Extensional Rheometer (CaBER), allows for the very first time performing electrorheometry under extensional flow. By means of the same experimental setup, this study investigates the influence of the polarity of the imposed electric field on the filament thinning process of a Newtonian and an electrorheological fluid. Results show that a polarity against the gravity results in filament thinning processes that live longer or reach a stable configuration at lower intensities of the applied electric field

Dolomitic lime: thermal decomposition of nesquehonite

Nesquehonite (MgCO3·3H2O) (N) can be obtained from a dolomitic quicklime paste in a CO2-rich atmosphere. Thermal decomposition of this synthetic nesquehonite has been studied by TG-DTA analysis. It is very similar to the hydromagnesite (HY) thermal decomposition, as it show similarities in the decarbonations at 440 and 550 °C, and an exothermic phenomenon at 510 °C. It has been reported in the literature that some intermediate in N→HY transformation occur, but this process cannot be directly detected during the heating. Samples were heated at 115, 230, 280, 370, 460, 520, 600, 800 and 1000 °C and XRD and FT-IR were used in order to determine the structural changes in nesquehonite and the intermediate phases formed. Results show that nesquehonite transforms at lower temperatures (115 °C) into a stable amorphous magnesium carbonate with chemical composition very close to that of HY. Thermal decomposition of nesquehonite, during a gradual temperature increase, proceeds via the formation of this compound. At higher temperatures (460 °C/short heating times), nesquehonite transforms into HY. The occurrence of an exothermic peak at 510 °C has been also discussed

Dolomitic limes: evolution of the slaking process under different conditions

Dolomitic lime-based pastes were prepared in order to study the evolution of the compounds during the slaking process. Thermal studies as well as X-ray diffraction and FT-IR spectroscopy were used to confirm the formed compounds. The rate of the hydration of calcium and magnesium oxides has been determined under different conditions: atmospheric conditions, CO2-rich and enclosed environment without CO2. Also the lime powder evolution without water added was studied. Whereas CaO hydrates at a higher rate, MgO is very dependent by its particle size distribution and stirring. The paper also focuses on the carbonation process. Given that carbonation is the most usual hardening process in lime pastes, its knowledge is necessary to understand the mechanical behavior of these pastes. In an excess of water, calcium hydroxide carbonates giving calcite if exposed to CO2. In lime powder, another mechanism has been established through vaterite formation. Magnesium hydroxide does not carbonate under normal conditions. In a CO2 atmosphere nesquehonite (MgCO3·3H2O) has been checked found as a result of carbonation

Dynamic tests and adaptive control of a bottoming organic Rankine cycle of IC engine using swash-plate expander

This paper deals with the experimental testing of a bottoming Organic Rankine Cycle (ORC) integrate in a 2 l turbocharged gasoline engine using ethanol as working fluid. The main components of the cycle are a boiler, a condenser, a pump and a swash-plate expander. Both steady and transient tests were performed in three engine operating points to understand the behavior and inertia of the system. Pressure-Volume diagram during these transients were presented and analyzed. Operating parameters of the expander, such as expander speed and boiler power, were shifted. The objective of these tests is to understand the inertia of the system and to have a robust control in all the possible transient tests. New European Driving Cycle was tested with and without the expander because it is supposed to represent the typical usage of a car in Europe. It was used to validate the control of the ORC in realistic dynamic conditions of the engine. The importance of each parameter was analyzed by fixing all the parameters, changing each time one specific value. The main result of this paper is that using a slightly simple and robust control based on adaptive PIDs, the two dynamic effects of an ORC could be taken into account, i.e. high inertia effects (boiler and condenser) and low inertia effects (pump and volumetric expander).This work is part of a research project called "Evaluation of bottoming cycles in IC engines to recover waste heat energies" funded by a National Project of the Spanish Government with reference TRA2013-46408-R. The authors thank also to Raul Lujan and Rafael Carrascosa for their contribution in the testing process. Authors want to acknowledge the "Apoyo para la investigacion y Desarrollo (PAID)" grant for doctoral studies (FPI S2 2015 1067).Torregrosa, AJ.; Galindo, J.; Dolz Ruiz, V.; Royo-Pascual, L.; Haller, R.; Melis, J. (2016). Dynamic tests and adaptive control of a bottoming organic Rankine cycle of IC engine using swash-plate expander. Energy Conversion and Management. 126:168-176. https://doi.org/10.1016/j.enconman.2016.07.078S16817612

Efficacy of different antifouling treatments for seawater cooling systems

In an industrial seawater cooling system, the effects of three different antifouling treatments, viz. sodium hypochlorite (NaClO), aliphatic amines (Mexel1432) and UV radiation, on the characteristics of the fouling formed were evaluated. For this study a portable pilot plant, as a side-stream monitoring system and seawater cooling system, was employed. The pilot plant simulated a power plant steam condenser, having four titanium tubes under different treatment patterns, where fouling progression could be monitored. The nature of the fouling obtained was chiefly inorganic, showing a clear dependence on the antifouling treatment employed. After 72 days the tubes under treatment showed a reduction in the heat transfer resistance (R) of around 70% for NaClO, 48% for aliphatic amines and 55% for UV, with respect to the untreated tube. The use of a logistic model was very useful for predicting the fouling progression and the maximum asymptotic value of the increment in the heat transfer resistance (DRmax). The apparent thermal conductivity (l) of the fouling layer showed a direct relationship with the percentage of organic matter in the collected fouling. The characteristics and mode of action of the different treatments used led to fouling with diverse physicochemical properties

Actividad ovárica y tasa de gestación en novillas suplementadas en el Trópico Húmedo de Costa Rica

Se determinó el efecto de la suplementación sobre la actividad ovárica y tasa de gestación en novillas Bosindicus (n=41) nulíparas de dos a tres años, divididas aleatoriamente en dos grupos: el suplementado (GS n=21) con un concentrado comercial (13,5% PC, 2,850 Mcal ED/kg MS) a razón del 1% del peso; con un periodo de 15 días de adaptación más 30 de suplementación y el testigo (GNS n=20). Ambos pastando Estrella Africana (Cynodonplestostachium), Ratana (Ischaemumindicum) y Tanzania (Panicummaximum); agua y sales minerales ad libitum). Las hembras se sincronizaron con Crestar® y servidas con dos toros de fertilidad probada. El diseño experimental fue al azar utilizando el programa estadístico JMP 10® de SAS Institute Inc. para el análisis. La condición corporal (CC) y grasa dorsal (GD) no son diferentes (P>0.05) así como los porcentajes entre grupos para actividad ovárica (ciclicidad y estructuras ováricas), tasa de preñez, los eventos de ciclicidad y gestación a lo largo del tiempo (P>0.05). La estimación de ocurrencia de la gestación en función del suplemento y la ciclicidad, según el modelo: Gest = f(GEST, CYC, TRAT) no mostró efecto del tratamiento (P>0.05) pero si significancia en los momentos de detección de la gestación (día 33 y día 45 respectivamente) entre grupos (P< 0.0001). En conclusión, el método de suplementación ensayado no tuvo mayor efecto sobre las variables estudiadas

Evolución tectónica y morfoestructural reciente de la Península Byers (Antártida): evidencias sobre el desarrollo de las Islas Shetland del Sur y la Cuenca de Bransfield

[EN] Byers Peninsula forms the western extremity of the Livingston Island (Antarctica) in the continental South Shetland Block. This tectonic block is bounded by the South Shetland Trench to the north, the Bransfield back-arc basin to the south, and extends to the South Scotia Ridge on the east. Westwards it is connected to the Antarctic Plate by a broad deformation zone located at the southern end of the Hero Fracture Zone. In Byers Peninsula we analyzed more than 1,200 lineaments, and 359 fault planes from 16 sites, both in sedimentary and intrusive igneous rocks. Statistical analysis of lineaments and mesoscopic fractures, with a length varying between 31 and 1,555 m, shows a NW-SE maximum trend, with two NE-SW and ENE-WSW secondary maximums. Fault orientation analysis shows similar trends suggesting that most of the lineaments correspond to fractures. Due to the absence of striated faults and the lack of kinematic evidence on the regime in most of the analyzed faults we have used the Search Grid paleostress determination method. The results obtained allow us to improve and complete the data on the recent evolution of the South Shetland Block. In this complex geodynamic setting, Byers Peninsula has been subjected to NNW-SSE to NNE-SSW extension related to Bransfield Basine Antarcopening and NE-SW and NW-SE local compressions respectively associated to Scotia-Antarctic plate convergence and the South Shetland Trench subduction.[ES] La Península Byers se localiza en el extremo occidental de la Isla Livingston (Antártida) que pertenece al bloque continental de las Shetland del Sur. Este bloque tectónico está limitado al norte por la Fosa de las Shetland del Sur, al sur por la cuenca de trasarco de Bransfield, y hacia el este se extiende por la Dorsal Sur de Scotia. Hacia el oeste conecta con la placa Antártica a través de una amplia zona de deformación localizada en la prolongación meridional de la Zona de Fractura Hero. En este trabajo se han analizado conjuntamente más de 1.200 lineamientos, así como 359 planos de fallas en 16 estaciones en rocas sedimentarias e ígneas de la Península Byers. El análisis estadístico de los lineamientos y las fracturas a escala mesoscópica, con una longitud que oscila entre 31 y 1.555 m, muestran una orientación máxima NO-SE, con dos máximos secundarios de dirección NE-SO y ENE-OSO. El análisis de las fracturas muestra orientaciones similares que sugieren que gran parte de estos lineamientos están relacionados con fracturas. La ausencia de indicadores cinemáticos de calidad en la mayor parte de las fracturas sólo nos ha permitido aplicar el método de Redes de Búsqueda para el cálculo de paleoesfuerzos. Los resultados obtenidos son compatibles con los obtenidos en otros sectores del Bloque de las Shetland del Sur. En este complejo contexto geodinámico, la Península Byers ha estado sometida a extensión NNW-SSE/ NNE-SSW ligada a la apertura de la cuenca de Bransfield, así como a compresión local NE-SO y NO-SE asociada respectivamente a la convergencia entre las placas Scotia y Antártica, y a la subducción en la Fosa de las Shetland del Sur.Financial support for this work was provided by the research projects REN2001-0643, CGL2005-03256 and CGL2007-28812-E/ANT of the Spanish R & D National Plan.Peer reviewe

Stabilized vortex solitons in layered Kerr media

In this letter we demonstrate the possibility of stabilizing beams with angular momentum propagating in Kerr media. Large propagation distances without filamentation can be achieved in layered media with alternating focusing and defocusing nonlinearities. Stronger stabilization can be obtained with the addition of an incoherent beam.Comment: 4 pages, 3 figures. We have removed the sentence "Thus, they erroneously point out to the existence of fully stabilized vortex solitons" in page 2, column 2, line 7-8, because it might be confusin

Analysis of the role of altitude on diesel engine performance and emissions using an atmosphere simulator

[EN] Forthcoming directives from European Commission will force homologation in altitude to approach standards to actual driving conditions in order to reduce the gap between regulated and real-life emissions. This work presents the use of a dedicated atmosphere simulator to analyse the impact of altitude on performance and emissions of a turbocharged diesel engine. The presented equipment provides engine intake and exhaust pressure to reproduce high-altitude conditions. The main advantages are related to cost savings with respect to round-robin testing campaigns ensuring controlled ambient conditions at the different altitudes. The paper shows the main features of the altitude simulator under steady-state and transient operation and the ability to control temperature at the same time that pressure according to International Standard Atmosphere (ISA) specifications. The experimental results highlight the need for specific testing facilities to perform calibration tasks as a key tool to comply with future emission standards in a cost-effective manner. In particular, regulated emissions measured at altitude are shown to clearly exceed that permitted at sea-level emphasizing the need to explore new dedicated engine control strategies for pollutant abatement under altitude operation.Bermúdez, V.; Serrano, J.; Piqueras, P.; Gómez-Gil, J.; Bender, S. (2017). Analysis of the role of altitude on diesel engine performance and emissions using an atmosphere simulator. International Journal of Engine Research. 18(1-2):105-117. doi:10.1177/1468087416679569S105117181-