Ferromagnetic (Ga,Mn)N epilayers versus antiferromagnetic GaMn3_3N clusters

Mn-doped wurtzite GaN epilayers have been grown by nitrogen plasma-assisted molecular beam epitaxy. Correlated SIMS, structural and magnetic measurements show that the incorporation of Mn strongly depends on the conditions of the growth. Hysteresis loops which persist at high temperature do not appear to be correlated to the presence of Mn. Samples with up to 2% Mn are purely substitutional Ga$_{1-x}$Mn$_x$N epilayers, and exhibit paramagnetic properties. At higher Mn contents, precipitates are formed which are identified as GaMn$_3$N clusters by x-ray diffraction and absorption: this induces a decrease of the paramagnetic magnetisation. Samples co-doped with enough Mg exhibit a new feature: a ferromagnetic component is observed up to $T_c\sim175$ K, which cannot be related to superparamagnetism of unresolved magnetic precipitates.Comment: Revised versio

Strategies to improve the energy efficiency of pressurized water systems

[EN] As time goes by, the need to move water is greater and this water will be pressurized. Layout flexibility, security, quality care, control, lower environmental impact and higher efficiency justify pressurized transport rather than natural gravitational water transport. On the negative side, we find the enormous amount of energy pressurized systems require with the associated negative economic and environmental impacts. Therefore, it is crucial to minimize these impacts and that only can be achieved by improving the energy efficiency of these systems. To achieve that final goal, the first step is to perform an assessment to estimate the margin of improvement from the actual performance of the system to the maximum achievable level of efficiency [1]. The second step is to perform an energy audit in order to identify exactly how the energy is used and where it is lost [2], with the third step being identification of the different actions that can be implemented in practice in a system. The final step is to perform the cost benefit analysis of the selected actions to prioritize execution. The focus of attention of this paper is on the third step, actions that can be classified in operational actions (do not require investments) and structural actions (require investments).Cabrera Marcet, E.; Gomez Selles, E.; Espert Alemany, VB.; Cabrera Rochera, E. (2017). Strategies to improve the energy efficiency of pressurized water systems. Procedia Engineering. 186:294-302. doi:10.1016/j.proeng.2017.03.248S29430218

A Mark in Time Saves Nein

A method for predicting political interactions and policy outcomes based on two political theorems is presented and illustrated with an examination of the decision to merge the two German currencies. Political perceptions and actions are anticipated by combining the substantive knowledge of area experts with the theoretical insights embedded in the median voter theorem and a monotonicity theorem that links expectations to probabilistic statements of action. The proposed model has proven accurate about 90 percent of the time. The proposed forecasting method identifies a sequential strategy that may have been followed by Chancellor Kohl in forging the coalition needed to merge successfully the two German currencies. Using comparative statics, the analysis suggests how subtle and sophisticated Chancellor Kohl had to be to succeed in getting the policy outcome he desired despite stiff opposition.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66924/2/10.1177_019251219201300106.pd

Energy Assessment of Pressurized Water Systems

[EN] This paper presents three new indicators for assessing the energy efficiency of a pressurized water system and the potential energy savings relative to the available technology and economic framework. The first two indicators are the ideal and real efficiencies of the system and reflect the values of the minimum energy required by users the minimum amount of energy to be supplied to the system (because of its ideal behavior) and the actual energy consumed. The third indicator is the energy performance target, and it is estimated by setting an ambitious but achievable level of energy loss attributable to inefficiencies in the system (e.g., pumping stations, leakage, friction loss). The information provided by these three key performance indicators can make a significant contribution towards increasing system efficiency. The real efficiency indicator shows the actual performance of the system; the energy performance target provides a realistic goal on how the system should be performing; and finally, the ideal efficiency provides the maximum and unachievable level of efficiency (limited by the topographic energy linked to the network topography). The applicability and usefulness of these metrics will be demonstrated with an application in a real case study.The authors acknowledge the very valuable contributions made by the reviewers of this paper, because their comments and suggestions have helped to significantly improve the contents. Additionally, we thank the staff of Aguas de Valencia for providing helpful advice and real case studies used to tune the software tool developed based on this paper. And last but not least, the research leading to these results received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement number 265122. The translation of this paper was funded by the Universitat Politècnica de València, Spain.Cabrera Marcet, E.; Gomez Selles, E.; Cabrera Rochera, E.; Soriano Olivares, J.; Espert Alemany, VB. (2014). Energy Assessment of Pressurized Water Systems. Journal of Water Resources Planning and Management. 141(8):1-12. https://doi.org/10.1061/(ASCE)WR.1943-5452.0000494S112141

Determination of the stress state in the Andean Cordillera Frontal near the border between Argentina and Chile

Fil: Martino, Roberto D. Universidad Nacional de Córdoba; Argentina.Fil: Martino, Roberto D. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones en Ciencias de la Tierra; Argentina.Fil: Giambastiani, Mauricio. Universidad Nacional de Córdoba; Argentina.Fil: Rocca, Ricardo J. Universidad Nacional de Córdoba; Argentina.Fil: Guereschi, Alina B. Universidad Nacional de Córdoba; Argentina.Fil: Guereschi, Alina B. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones en Ciencias de la Tierra; Argentina.Fil: Huerta Soaje, Pedro J. Universidad Nacional de Córdoba; Argentina.Fil: Marcet, Juan E. Universidad Nacional de San Juan; Argentina.The initial state of stress is an important parameter in underground excavations. From its knowledge, it is possible to calculate the stresses induced around the excavation and the necessary support for stabilization. This task becomes critical when the excavations have great dimensions such as caverns and when rock overburden is significant. Different methodologies are discussed, including simple regional stress maps, the survey of surface paleostress and hydraulic fracturing executed in borehole between 500 and 800 m deph. These methodologies have been applied in the Andean Cordillera Frontal, where the Agua Negra tunnel will be built between Argentina and Chile. This area is affected by the subduction of the Nazca plate beneath the South American plate. This setting generates that the greatest principal stress σ1 has a W-E orientation and relationship with the vertical stress (σ2) reaches about 1.4.Fil: Martino, Roberto D. Universidad Nacional de Córdoba; Argentina.Fil: Martino, Roberto D. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones en Ciencias de la Tierra; Argentina.Fil: Giambastiani, Mauricio. Universidad Nacional de Córdoba; Argentina.Fil: Rocca, Ricardo J. Universidad Nacional de Córdoba; Argentina.Fil: Guereschi, Alina B. Universidad Nacional de Córdoba; Argentina.Fil: Guereschi, Alina B. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones en Ciencias de la Tierra; Argentina.Fil: Huerta Soaje, Pedro J. Universidad Nacional de Córdoba; Argentina.Fil: Marcet, Juan E. Universidad Nacional de San Juan; Argentina.Geologí

Electric-field-induced coherent coupling of the exciton states in a single quantum dot

The signature of coherent coupling between two quantum states is an anticrossing in their energies as one is swept through the other. In single semiconductor quantum dots containing an electron-hole pair the eigenstates form a two-level system that can be used to demonstrate quantum effects in the solid state, but in all previous work these states were independent. Here we describe a technique to control the energetic splitting of these states using a vertical electric field, facilitating the observation of coherent coupling between them. Near the minimum splitting the eigenstates rotate in the plane of the sample, being orientated at 45{\deg} when the splitting is smallest. Using this system we show direct control over the exciton states in one quantum dot, leading to the generation of entangled photon pairs

Sustitución de bombeos aspirando de depósitos de rotura de carga por bombeos con aspiración directa de red. El caso de la estación de bombeo de Adsubia-Cabanes (Jávea)

[ES] En sistemas de distribución de agua urbanos, en los puntos donde la presión es insuficiente para abastecer adecuadamente una parte de la red, se instalan estaciones de bombeo que refuerzan la presión solamente en esta parte del sistema. Es el caso, por una parte, de los grupos hidropresores instalados en edificios altos, mediante los cuales se puede suministrar sin problemas a partir de aproximadamente el tercero o cuarto piso. Y por otra parte están las estaciones de bombeo que impulsan el agua de la red hacia sectores con cota elevada, los cuales no pueden ser suministrados directamente desde el o los puntos de cabecera del sistema. Tanto en unos casos como en otros la aspiración de los grupos de bombeo se puede realizar desde depósitos a presión atmosférica, los cuales se alimentan del agua de la red (depósitos de rotura de carga), o bien aspirando directamente de la propia red. En el caso del bombeo desde depósitos de rotura de carga el agua de alimentación de los grupos de bombeo se despresuriza al entrar al depósito, perdiendo la energía de presión de la que dispone en el interior de la red (Cobacho et al., 2012). En este caso los transitorios de puesta en marcha o parada de los grupos de bombeo no afectan al sistema de distribución. En el caso de aspiración directa de red se aprovecha la energía de presión del agua aspirada, con lo cual la altura de bombeo y la energía consumida en la impulsión son menores. Esta es una razón importante que justifica la adopción de esta solución, máxime con el ahorro en potencia contratada y en consumo energético que se puede conseguir. Además, de esta manera se contribuye a la reducción de emisiones de gases de efecto invernadero que supone el ahorro en consumo energético (Basupi et al., 2014). Pero en contra de esta solución actúa el hecho de que los transitorios originados por las maniobras de los grupos de bombeo pueden llegar a afectar a la red (Davis, 210; Soriano et al., 2014), lo que obliga en instalaciones de importancia a disponer de adecuados sistemas de protección contra transitorios hidráulicos. En este sentido, la presente comunicación trata sobre la sustitución de los grupos de la estación de bombeo de Adsubia-Cabanes, la cual ha estado aspirando de un depósito de rotura de carga alimentado desde la red de distribución de agua potable de Jávea, por nuevos grupos de bombeo con aspiración directa de red. Se definen además los sistemas de protección contra transitorios hidráulicos a instalar tanto en la parte de aspiración como en la de impulsión de la estación de bombeo modificada, en los cuales se combinan calderines con válvulas de protección. Para llevar a cabo el estudio se utiliza el programa Allievi para cálculo y simulación de transitorios hidráulicos.Espert Alemany, VB.; Henarejos Cardona, J.; Cabrera Marcet, E.; Ladrón De Guevara Diego, P. (2015). Sustitución de bombeos aspirando de depósitos de rotura de carga por bombeos con aspiración directa de red. El caso de la estación de bombeo de Adsubia-Cabanes (Jávea). Universidad de Córdoba. 1005-1014. http://hdl.handle.net/10251/141657S1005101