Spacecraft Low Thrust Propulsion Optimization System

As we advance into a modern space-age there is a need to obtain better trajectories for spacecraft missions, in which optimization plays an integral role. These improved trajectories will provide a more cost efficient means of conducting space missions. Throughout this paper such optimization will be discussed in terms of accomplishment and potential problems. Previous trajectory optimization research efforts include using the idea that the shape-based solution is only near-optimal and as a result there should exist a neighboring solution with a lower cost. Using Linear Quadratic Regulator (LQR) control and linearized equations about the nominal shape-based trajectory, a shape-smoothing algorithm is built that improves the cost of the trajectory. This LQR algorithm also addresses the 2 drawbacks. First, the LQR removes the constraint that the in-plane thrust vector be parallel to the velocity vector. This improves the thrust pointing angle guess for any further optimization method. Second, since the overall thrust level does typically (but is not guaranteed to) decrease, the initial thrust acceleration for the LQR trajectory is lower than that of the shape-based method. This helps (but still does not guarantee that) the initial thrust acceleration for the LQR trajectory to be equal to or less than what the physical hardware can provide. As a continuation of previous research the LQR optimization method was used for multi-body target trajectory. Multiple examples were created ranging from one body to three body trajectories in order to verify the accuracy of the method compared to others that have been used

Regionalization and connectivity in the Gulf of Cádiz and Alborán Sea implication for marine spatial planning and coastal management

This work proposes a regionalization of marine waters south of the Iberian Peninsula based on empirical orthogonal functions and GIS analysis. The regions identified are consistent and correspond to hydrological mesoscale and macroscale structures well characterized from physical and biological viewpoints. Although it is difficult to determine the boundaries of a fluid continuously moving, the procedure used recognizes the most frequent patterns and can be used to reference geographically the most likely position of the limit among the regions. Once established the regions, the connectivity among them is addressed by means of geostrophic currents derived from altimetry data. The main geostrophic circulation pattern depict an elevate connectivity in the area that might facilitate the conservation and recovering of species, but also imply a higher vulnerability to negative externalities and highlight the need of models, marine spatial planning, and coastal management approaches that includes the pelagic ecosystem and connectivity of the seas. Furthermore, the results confirm that the cooperation between public authorities at different levels (local, regional, state) as well as among riparian countries is essential for marine spatial planning and prevention of potential risk derived from upcoming marine activities in the framework of the 2020 agenda and Blue Growth strategy.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Estudio in vitro de microfiltracion de dos sistemas adhesivos en sellantes

62 p.Debido al progreso importante en el diseño de materiales y nuevas tecnicas que reducen los problemas de micro filtración en la odontología, surge la necesidad de conocer y estudiar el comportamiento marginal de los nuevos materiales para el sellado de fosas y fisuras. En el mercado han aparecido materiales que simplifican el accionar clínico, come los primer de auto grabado, con una manipulación mas rápida, y también materiales que mejoran la biomecánica del sellarte como los adhesivos de quinta generación. En nuestros tiempos, el uso del sellante convencional esta siendo modificado, debido a problemas en su aplicación, principalmente la contaminación con saliva después del grabado ácido, que provoca la micro filtración o la perdida del sellante. Para solucionar este problema aparece el uso del adhesivo acompañando al sellante. Hitt y Feigal en 1992 fueron los primeros en reportar los beneficios de aplicar un agente de unión dentinarío entre el esmalte grabado y el sellante como una forma de optimizar la fuerza de unión en un caso de humedad o contaminación salivaria. Otros estudios han confirmado los beneficios de los agentes de unión bajo los sellantes en esmalte contaminado, los cuales mejoran el éxito clínico a corto tiempo, reducen la micro filtración, refuerzan la fluidez de la resina dentro de la fisura e incrementan la fuerza de unión. El propósito de este estudio in vitro, fue comparar los valores de micro filtración en dos grupos de sellantes: un sellante mas un adhesivo de quinta generacion; y otro grupo de sellantes mas un primer de autograbado. Ambos grupos estarán sometidos a un proceso de ciclado térmico y a un proceso de cargas. El proceso del termo ciclado es para simular las condiciones intraorales adversas que pueden ser inducidas por la comida, bebida o la respiración, junto a un proceso de envejecimiento acelerado. Las cargas son para simular el intenso estrés oclusal que sufren las piezas dentarias durante la función normal y la parafuncion. Los objetivos de este estudio fueron comparar los valores de micro filtración entre los dos grupos de sellantes, determinando la micro filtración en cada grupo por separado. Para realizar este estudio se seleccionaron treinta y seis piezas dentarias extraídas por razones ortodoncicas, molares y premolares sin caries, los cuales fueron divididos al azar en dos grupos, y sellados en todas sus fisuras con el sellante y el adhesivo correspondiente. Posteriormente, las muestras se sometieron al proceso de cargas donde se aplicaron 250 ciclos de 10 Kg. 0 98 N. por 0.5 segundos en la fosa central del diente sobre el sellante. Luego, las muestras fueron sometidas a 300 ciclos térmicos, permaneciendo posteriormente 24 horas en una solución de tincion de azul de metileno al 0,2%, para finalmente cortar las muestras a través del sellante y observar y cuantificar la penetración del agente colorante en la interfase sellante-esmalte. Los resultados fueron sometidos al análisis de discrepancia estadística de Kruskall Wallis con un nivel de significancia del 95%. El test estadístico fue realizado con el software Stat Graphic Plus for Windows, Versión 1.4 ( Manugistic, Inc., Rockville, MD ). Los resultados revelan que ambos grupos de sellantes presentan un gran numero de piezas dentarias con microfiltracion grado 3. No obstante, existen diferencias significativas entre ambos, presentando un menor numero de piezas dentarias con micro filtración el grupo de sellantes que se realizo con un adhesivo de quinta generación (p=0,037878 )

English Communication for International Business II

Llibre i audioENGLISH COMMUNICATION FOR INTERNATIONAL BUSINESS II is the second book of a collection oftwo addressed to those students involved in learning English to communicate in business contexts. As the previous one, the book is conceived as self-learning material which includes the keys to most activities although the support ofthe instructor in the classroom becomes necessary for some of them. This book is content-based, trying to emphasise the written and oral communicative necessities of the international business world. The book is organised in six units which deal with some types ofbusiness written and oral communication, such as meetings and negotiations, international trade procedures related to Incoterms, packing, delivery and insurance, methods of payment and their corresponding documents, orders, and complaints. All units deal with reading, writing, and listening skills, as well as translation. The CD provided with the book is higWy useful for the listening activities. Speaking and interaction can also be worked in all units although always with the teacher's guidance. Each unit starts with a general explanation of the topic, followed by reading comprehension and vocabulary activities. Along the unit, several specific explanations can be found including examples of the documents and of the written and spoken communicative events involved. Students are then required to produce their own documents and effective pieces of communication. At the end of each unit, two communicative situations have been included, asking students to solve a business problem. After the situations, each unit is provided with references for further reading either in books or in websites. As a complement to the units in both volumes, a series of seventeen case studies have been created. These case studies reproduce real situations in a company, such as launching a new product, hiring a new employee, strategies to sell a product, reacting to claims, negotiating staff reduction, etc

A Bilevel Approach to Optimal Price-Setting of Time-and-Level-of-Use Tariffs

Time-and-Level-of-Use (TLOU) is a recently proposed pricing policy for energy, extending Time-of-Use with the addition of a capacity that users can book for a given time frame, reducing their expected energy cost if they respect this self-determined capacity limit. We introduce a variant of the TLOU defined in the literature, aligned with the supplier interest to prevent unplanned over-consumption. The optimal price-setting problem of TLOU is defined as a bilevel, bi-objective problem anticipating user choices in the supplier decision. An efficient resolution scheme is developed, based on the specific discrete structure of the lower-level user problem. Computational experiments using consumption distributions estimated from historical data illustrate the effectiveness of the proposed framework

Translocation of a polymer chain driven by a dichotomous noise

We consider the translocation of a one-dimensional polymer through a pore channel helped by a motor driven by a dichotomous noise with time exponential correlation. We are interested in the study of the translocation time, mean velocity and stall force of the system as a function of the mean driving frequency. We find a monotonous translocation time, in contrast with the mean velocity which shows a pronounced maximum at a given frequency. Interestingly, the stall force shows a nonmonotonic behavior with the presence of a minimum. The influence of the spring elastic constant to the mean translocation times and velocities is also presented.Comment: 11 pages, 7 figure

Variational principles and finite element Bloch analysis in couple stress elastodynamics

We address the numerical simulation of periodic solids (phononic crystals) within the framework of couple stress elasticity. The additional terms in the elastic potential energy lead to dispersive behavior in shear waves, even in the absence of material periodicity. To study the bulk waves in these materials, we establish an action principle in the frequency domain and present a finite element formulation for the wave propagation problem related to couple stress theory subject to an extended set of Bloch-periodic boundary conditions. A major difference from the traditional finite element formulation for phononic crystals is the appearance of higher-order derivatives. We solve this problem with the use of a Lagrange-multiplier approach. After presenting the variational principle and general finite element treatment, we particularize it to the problem of finding dispersion relations in elastic bodies with periodic material properties. The resulting implementation is used to determine the dispersion curves for homogeneous and porous couple stress solids, in which the latter is found to exhibit an interesting bandgap structure.Comment: 29 pages, 8 figure

Carbon-fiber tips for scanning probe microscopes and molecular electronics experiments

We fabricate and characterize carbon-fiber tips for their use in combined scanning tunneling and force microscopy based on piezoelectric quartz tuning fork force sensors. An electrochemical fabrication procedure to etch the tips is used to yield reproducible sub-100-nm apex. We also study electron transport through single-molecule junctions formed by a single octanethiol molecule bonded by the thiol anchoring group to a gold electrode and linked to a carbon tip by the methyl group. We observe the presence of conductance plateaus during the stretching of the molecular bridge, which is the signature of the formation of a molecular junction.Comment: Conference Proceeding (Trends in NanoTechnology 2011, Tenerife SPAIN); Nanoscale Research Letters, (2012) 7:25

Effect of tibolone on breast cancer cell proliferation in postmenopausal ER+ patients: Results from STEM trial

Purpose: Tibolone is a selective tissue estrogenic activity regulator, approved for the treatment of vasomotor symptoms in postmenopausal women. We have done an exploratory, double-blind, randomized, placebo-controlled pilot trial to investigate the tissue-specific effects of 2.5 mg tibolone on breast cancer in postmenopausal women, in particular on tissue proliferation (STEM, Study of Tibolone Effects on Mamma carcinoma tissue). Experimental Design: Postmenopausal women with initially stage I/II, estrogen receptor-positive (ER+) primary breast cancer, were randomly assigned to 14 days of placebo or 2.5 mg/d tibolone. Core biopsies of the primary tumor were obtained before and after treatment. Ki-67 and apoptosis index were analyzed in baseline and corresponding posttreatment specimen. Results: Of 102 enrolled patients, 95 had evaluable data. Baseline characteristics were comparable between both treatment groups. Breast cancer cases are mainly invasive (99%), stage I or II (42% and 50% respectively), and ER+ (99%). Median intratumoral Ki-67 expression at baseline was 13.0%, in the tibolone group and 17.8% in the placebo group, and decreased to 12.0% after 14 days of tibolone while increasing to 19.0% in the placebo group. This change from baseline was not significantly different between tibolone and placebo (Wilcoxon test; P = 0.17). A significant difference was observed between the treatment groups when the median change from baseline apoptosis index was compared between the treatment groups (tibolone, 0.0%; placebo, +0.3%; Wilcoxon test; P = 0.031). The incidence of adverse effects was comparable. Conclusions: In ER+ breast tumors, 2.5 mg/d tibolone given for 14 days has no significant effect on tumor cell proliferation