Optimizing the Density of Holes of EWT Solar Cells Taking Into Consideration Mechanical Aspects

EWT solar cells start from drilled wafers with approximately 100 holes/cm2. These holes act as stress concentrators leading to a reduction in the mechanical strength of this type of wafers. The viability of cells with higher density of holes has been studied. To this end, sets of wafers with different density of holes have been characterized. The ring on ring test has been employed and FE models have been developed to simulate the test. The statistical evaluation permits to draw conclusions about the reduction of the strength depending on the density of holes. Moreover, the stress concentration around the holes has been studied by means of the FE method employing the sub-modeling technique. The maximum principal stress of EWT wafers with twice the density of holes of commercial ones is almost the same. However, the mutual interaction between the stress concentration effects around neighboring holes is only observed for wafers with a density of 200 holes/cm

Current status and trends of african migration to Spain

Una versió de l'article va ser presentada al Congrés Beyond Plurality in the African Diaspora: Ethnicity, Congregation, Networking and Citizenship. Keele University, del 25 al 27 de setembre de 2008.From the beginning of the 21st Century, Spain has experienced a migratory boom reaching the top of the European Union's destination countries, not only with respect to inflows - with more than three million people from 2000 to 2006- but to population stocks with 4,519,554 non-native residents in 2007 (10 percent of the registered population). The recent migratory wave -led by Latin-Americans- has changed the foreign population's composition traditionally dominated by Moroccans. African origin migrants, who represent 19 percent (860,217 people) of the immigrant population in 2007, have experienced a double effect during the same period. First, positive discrimination favoring LatinAmericans has apparently compromised the settlement process of African nationals. Second, restrictive immigration policies have also affected the composition of African inflows. Traditionally composed by Moroccans (13.75 percent of the 2007 foreign population), Gambians (0.31 percent) or Senegalese (0.79 percent) nationals, new sending countries have emerged during the last years. That is the case of Algeria (1.11 percent), Nigeria (0.66 percent) and Equatorial Guinea (0.44 percent). The aim of this paper is to analyze and contextualize the recent heterogeneous African diaspora in Spain under the socio-demographic point of view. Our findings will shed some light to the differential demographic behaviors of this group, particularly with respect to fertility and reproductive behavior.Des de començaments del segle XXI, Espanya ha experimentat un increment migratori notable, fins a situar-se com un dels principals països de destinació de la Unió Europea, no només pel que fa a les entrades (més de tres milions de persones, de 2000 a 2006) sinó també pel nombre de població de nacionalitat estrangera (al 2007, 4.519.554 persones, un 10% de la població de dret). L'actual onada immigratòria, encapçalada pels llatinoamericans, ha fet canviar la composició tradicional de la població estrangera que, fins feia poc, estava dominada pels marroquins. Els immigrants d'origen africà, que representen el 19% (860.217 persones) de la població immigrant al 2007, han experimentat un doble efecte: en primer lloc, la discriminació positiva cap a la població llatinoamericana no ha afavorit el seu procés d'integració; en segon lloc, les polítiques d'immigració restrictives també han afectat a la composició dels fluxos d'africans. La composició de la població africana estava formada per marroquins (13,75% de la població estrangera al 2007), gambians (0,31%) i senegalesos (0.79 %). En els darrers anys, nous països han entrat en escena, com Algèria (1,11%), Nigèria (0,66%) i Guinea Equatorial (0,44%). Davant aquest escenari, l'article analitza i contextualitza l'actual i heterogènia diàspora africana a Espanya, des del punt de vista sociodemogràfic. Els resultats permeten entendre els actuals comportaments demogràfics diferencials d'aquest grup, en particular pel que fa a la fecunditat i al comportament reproductiu.Desde inicios del siglo XXI, España ha experimentado un incremento migratorio notable, situándose como uno de los principales países de destino de la Unión Europea, no sólo en cuanto a las entradas (más de tres millones de personas, de 2000 a 2006) sino también por el número de población de nacionalidad extranjera (en 2007, 4.519.554 personas, un 10% de la población de derecho). La actual ola migratoria, encabezada por los latinoamericanos, ha hecho cambiar la composición tradicional de la población extranjera, hasta hace poco dominada por los marroquíes. Los inmigrantes de origen africano, que representan el 19% (860.217 personas) de la población inmigrante en 2007, han experimentado un doble efecto: en primer lugar, la discriminación positiva hacia la población latinoamericana no ha favorecido su proceso de integración; en segundo lugar, las políticas de inmigración restrictivas también han afectado a la composición de los flujos de africanos. La composición de la población africana estaba formada por marroquíes (13,75% de la población extranjera en 2007), gambianos (0,31%) i senegaleses (0.79%). En los últimos años, nuevos países han entrado en escena, como Argelia (1,11%), Nigeria (0,66%) y Guinea Ecuatorial (0,44%). Ante este escenario, el artículo analiza y contextualiza la actual y heterogénea diáspora africana en España desde el punto de vista sociodemográfico. Los resultados permitirán entender los actuales comportamientos demográficos diferenciales de este grupo, en particular en cuanto a la fecundidad y al comportamiento reproductivo

Migración interna y migración internacional en las estrategias familiares de reproducción : el caso de las poblaciones rurales del sur del estado de Veracruz

Este trabajo analiza la actual movilidad que afecta a las familias rurales del sur del estado de Veracruz, México. Las causas de esta movilidad están asociadas en la región de origen a las transformaciones derivadas del proceso de transición demográfica, de la crisis económica de comienzos de la década de 1980 y al nuevo modelo de desarrollo, y por último a la Reforma legal de 1992 sobre la propiedad social de la tierra. Estos factores han llevado a que la movilidad laboral en la región, tradicionalmente circunscrita a las familias de escasos recursos y contenida en el ámbito regional, haya dejado paso a un proceso de movilidad generalizado al conjunto de las familias rurales y a la emergencia de nuevos destinos, la frontera norte y los Estados Unidos, mercados con un gran dinamismo económico y fuertemente demandantes de mano de obra.Aquest treball analitza l'actual mobilitat que afecta a les famílies rurals del sud de l'estat de Veracruz, Mèxic. Les causes d'aquesta mobilitat estan associades a la regió d'origen, a les transformacions derivades del procès de transició demogràfica, de la crisis econòmica de principis de la dècada de 1980 i al nou model de desenvolupament, i per últim a la Reforma legal de 1992 sobre la propietat social de la terra. Aquest factors han fet que la mobilitat laboral de la regió, tradicionalment circunscrita a les famílies de pocs recursos i continguda en l'àmbit regional, hagi deixat pas a un procès de mobilitat generalitzat al conjunt de les famílies rurals i al surgiment de nous destins, la frontera nort i els Estats Units, mercats amb un gran dinamisme econòmic i fortament demandants de mà d'obra.This working paper analyzes the present mobility that affects the rural families of the south of the state of Veracruz, Mexico. The causes of this mobility are associate in the region of origin to the transformations derived from the process of demographic transition, the economic crisis of beginnings of the decade of 1980 and to the new model of development, and finally to the legal Reformation of 1992 on the social earth property. These factors have taken to that labor mobility in the region, traditionally circumscribed to the families of limited resources and contained in the regional scope, has opened the way to a process of mobility generalized to the set of the rural families and to the emergency of new destinies, the North border and the United States, markets with a great economic dynamism and strongly plaintiffs of manual labor

Level II reliability methods for tunnels

In tunnel construction, as in every engineering work, it is usual the decision making, with incomplete data. Nevertheless, consciously or not, the builder weighs the risks (even if this is done subjectively) so that he can offer a cost. The objective of this paper is to recall the existence of a methodology to treat the uncertainties in the data so that it is possible to see their effect on the output of the computational model used and then to estimate the failure probability or the safety margin of a structure. In this scheme it is possible to include the subjective knowledge on the statistical properties of the random variables and, using a numerical model consistent with the degree of complexity appropiate to the problem at hand, to make rationally based decisions. As will be shown with the method it is possible to quantify the relative importance of the random variables and, in addition, it can be used, under certain conditions, to solve the inverse problem. It is then a method very well suited both to the project and to the control phases of tunnel construction

AMH sérico pode predizer o risco de cancelamento de ciclo e as chances de boa resposta ovariana, independentemente da idade ou FSH

In the recent years, anti-Müllerian hormone (AMH) has been shown to represent a reliable marker of the ovarian reserve. In this study, we evaluate the risk of cycle cancellation and the chances of good ovarian response to controlled hyperstimulation and of pregnancy according to serum AMH measured prior to assisted reproduction procedures in females undergoing intracytoplasmic sperm injection. An analytic observational study included females undergoing ICSI between in a single center. Subgroup analyses were performed by grouping patients according to FSH levels or to their age. The risk of cycle cancellation decreased from 64% in patients with serum AMH ≤3 pmol/L (0.42 ng/mL) to 21% with AMH ≥15 pmol/L (2.10 ng/mL). The rate of good response increased from almost null in patients with AMH ≤3 pmol/L to 61% in those with AMH ≥15 pmol/L. Pregnancy rate increased moderately, but significantly, from 31% with AMH ≤3 pmol/L to 35% with AMH ≥15 pmol/L. Here we provide estimates of those outcomes according to the values of serum AMH, in general and in subgroups according to patient’s age or serum FSH, which are helpful for the clinician and the couple in their decision making about starting an ART treatment.Nos últimos anos, o hormonio anti-mülleriano (AMH) tem sido demonstrado como um marcador confiável da reserva ovariana. Neste estudo, avaliamos o risco de cancelamento do ciclo e as chances de boa resposta ovariana à hiperestimulação controlada e de gravidez, de acordo com o HAM no soro, medido antes de procedimentos de reprodução assistida em mulheres submetidas à injeção intracitoplasmática de espermatozóides. Um estudo analítico observacional incluiu mulheres submetidas a ICSI em um único centro. As análises dos subgrupos foram realizadas em pacientes agrupadas de acordo com os níveis de FSH ou para a sua idade. O risco de cancelamento do ciclo diminuiu de 64% em doentes com níveis séricos de HAM ≤% 3 pmol / L (0,42 ng / mL) a 21% com HAM ≥ 15 pmol / L (2,10 ng / mL). A taxa deboa resposta aumentou de quase nula em pacientes com HAM ≤ 3 pmol / L a 61% naqueles com AMH ≥ 15 pmol / L. A taxa de gravidez aumentou moderada, mas significativamente, de 31%, com HAM ≤ 3 pmol / L até 35% com HAM ≥ 15 pmol / L. Aqui fornecemos estimativas desses resultados de acordo com os valores de HAM no soro, em geral e em subgrupos de acordo com a idade do paciente ou de FSH, que são úteis para o clínico e para o casal em sua tomada de decisão sobre como iniciar um tratamento de RA.Fil: Calamera, Patricio. Centro Médico Seremas; ArgentinaFil: Buffone, Mariano Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; ArgentinaFil: de Vincentiis, Sabrina. Centro Médico Seremas; ArgentinaFil: Rey, Rodolfo Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Investigaciones Endocrinológicas; ArgentinaFil: Brugo Olmedo, Santiago. Centro Médico Seremas; Argentin

Modelos numéricos para el estudio de la ventilación en túneles

En túneles con ventilación longitudinal la actuación sobre los ventiladores es fundamental para evitar una catástrofe en caso de accidente con fuego. En este artículo se presentan tres modelos de cálculo que permiten el estudio de estas situaciones

Combining a Similar Coefficient Identification Algorithm with the Boundary Element Method

The boundary element method (BEM) has been applied successfully to many engineering problems during the last decades. Compared with domain type methods like the finite element method (FEM) or the finite difference method (FDM) the BEM can handle problems where the medium extends to infinity much easier than domain type methods as there is no need to develop special boundary conditions (quiet or absorbing boundaries) or infinite elements at the boundaries introduced to limit the domain studied. The determination of the dynamic stiffness of arbitrarily shaped footings is just one of these fields where the BEM has been the method of choice, especially in the 1980s. With the continuous development of computer technology and the available hardware equipment the size of the problems under study grew and, as the flop count for solving the resulting linear system of equations grows with the third power of the number of equations, there was a need for the development of iterative methods with better performance. In [1] the GMRES algorithm was presented which is now widely used for implementations of the collocation BEM. While the FEM results in sparsely populated coefficient matrices, the BEM leads, in general, to fully or densely populated ones, depending on the number of subregions, posing a serious memory problem even for todays computers. If the geometry of the problem permits the surface of the domain to be meshed with equally shaped elements a lot of the resulting coefficients will be calculated and stored repeatedly. The present paper shows how these unnecessary operations can be avoided reducing the calculation time as well as the storage requirement. To this end a similar coefficient identification algorithm (SCIA), has been developed and implemented in a program written in Fortran 90. The vertical dynamic stiffness of a single pile in layered soil has been chosen to test the performance of the implementation. The results obtained with the 3-d model may be compared with those obtained with an axisymmetric formulation which are considered to be the reference values as the mesh quality is much better. The entire 3D model comprises more than 35000 dofs being a soil region with 21168 dofs the biggest single region. Note that the memory necessary to store all coefficients of this single region is about 6.8 GB, an amount which is usually not available with personal computers. In the problem under study the interface zone between the two adjacent soil regions as well as the surface of the top layer may be meshed with equally sized elements. In this case the application of the SCIA leads to an important reduction in memory requirements. The maximum memory used during the calculation has been reduced to 1.2 GB. The application of the SCIA thus permits problems to be solved on personal computers which otherwise would require much more powerful hardware

Engineering repressors with coevolutionary cues facilitates toggle switches with a master reset

Engineering allosteric transcriptional repressors containing an environmental sensing module (ESM) and a DNA recognition module (DRM) has the potential to unlock a combinatorial set of rationally designed biological responses. We demonstrated that constructing hybrid repressors by fusing distinct ESMs and DRMs provides a means to flexibly rewire genetic networks for complex signal processing. We have used coevolutionary traits among LacI homologs to develop a model for predicting compatibility between ESMs and DRMs. Our predictions accurately agree with the performance of 40 engineered repressors. We have harnessed this framework to develop a system of multiple toggle switches with a master OFF signal that produces a unique behavior: each engineered biological activity is switched to a stable ON state by different chemicals and returned to OFF in response to a common signal. One promising application of this design is to develop living diagnostics for monitoring multiple parameters in complex physiological environments and it represents one of many circuit topologies that can be explored with modular repressors designed with coevolutionary information

Modelos numéricos para el estudio de incendios en túneles

Si se estudian los distintos métodos existentes actualmente para el estudio del comportamiento de los incendios en túneles no parece que se disponga de una solución única y definitiva. Tanto los métodos numéricos como los modelos fisicos a escala tienen sus limitaciones y ventajas. Por tanto, puede decirse que se trata de enfoques complementarios y que deben emplearse todos cuando la importancia de la obra así lo requiera.Desde el punto de vista del proyecto cabe indicar la necesidad de que los cálculos no se limiten al dimensionamiento del sistema de ventilación sino que incluyan pautas de actuación sencillas que puedan ser seguidas de forma refleja por los responsables del Centro de Control en los primeros momentos del incendio ya que ello es clave en el éxito del proceso de evacuación. En este sentido es perentorio el desarrollo de simuladores numéricos que puedan ser utilizados en el entrenamiento y formación de los operadores del Centro de Control