Characterization and improvement of a hybrid chemical rocket

The concerning project addresses a theoretical and practical analysis of an improved small hybrid rocket prototype. The main characteristics of the motor are: a fuel-oxidizer combination consisting of a hollow cylinder of PMMA and pure oxygen injected at high pressure (3-4 bar), and a pure convergent nozzle for which several values of the throat diameter were be tested. The main goal of the project was to characterize the rocket performance. In order to do so, first it was necessary to perform some physical improvements such as the inclusion of a pressure transducer for the estimation of the oxygen flow rate, as well as the redesign of the supporting structure and the amelioration of the data acquisition system for the obtaining of meaningful thrust readings. Moreover, a theoretical one-dimensional model was develop to contrast the empirical data and ensure its validity. Finally, three parametric studies were performed for which several experiments with different combinations of nozzle throat diameter, fuel cartridge length and oxygen tank pressure setting were carried out. The relevance of this project is significant given that this was the first phase of this prototype in which meaningful results were obtained. From the experimental phase, it was possible to conclude that the oper-ation of the device was highly transient and that the feeding oxygen orifice did not reach sonic conditions during operation against the expectations. Additionally, the correlation between the theoretical model and the empirical data showed an acceptable fitting, and although the lack of chamber temperature measure-ment was an inconvenient, it was possible to estimate the said parameter from the previous results. Finally, with respect to the parametric studies, it was concluded that: the low oxygen pressure ultimately caused that the reduction of the fuel cartridge length had no effect on the rocket performance; the largest nozzle (6mm throat diameter) coincided with the critical pressure ratio, and consequently, the smallest nozzle (4mm throat diameter) was clearly choked, although the increase in the rocket thrust was not very significant; the increase of the tank pressure was the most efficient way to increase the performance of the motor. Ultimately, it was concluded that a considerably higher thrust force could be achieved by performing future physical improvements to the deviceIngeniería Aeroespacia

Smoking among college students: characterization of use in the students' perspective

El objetivo fue conocer los significados atribuidos al consumo de tabaco entre estudiantes universitarios recién ingresados en la Universidad de Tegucigalpa, Honduras. Se trata de un estudio cualitativo con referencial metodológico fundamentado en el interaccionismo simbólico. Se formaron cuatro grupos focales (10 a 12) de estudiantes de distintas carreras, de ambos sexos, fumadores y no fumadores. Las principales categorías de significados acerca del consumo de tabaco fueron la presencia de fumadores en las familias de origen y los espacios para la iniciación del consumo de tabaco. Entre las razones para el inicio en el consumo de tabaco se encontraron factores como influencia de amigos y compañeros de trabajo. La práctica de deportes y los compromisos personales fueron atribuidos como factores no favorables al uso de tabaco. Se concluye que la universidad es un espacio abierto para el desarrollo de la promoción de estrategias educativas y preventivas frente al uso de drogas.O objetivo foi conhecer os significados atribuídos ao consumo de tabaco entre estudantes universitários de primeiro ano, da universidade de Tegucigalpa, Honduras. Trata-se de estudo qualitativo, e como referencial metodológico fundamentou-se no interacionismo simbólico. Realizaram-se quatro grupos focais (10 a 12) de estudantes de cursos distintos, de ambos os sexos, fumantes e não fumantes. As principais categorias de significados, a respeito do consumo de tabaco, foram presença de fumantes nos famílias de origem e os espaços para o início do consumo de tabaco. Entre as razões para o início do consumo de tabaco, foi indicada a influência de amigos e companheiros de trabalho. A prática de esportes e os compromissos pessoais foram atribuídos como fatores que não favorecem o consumo de tabaco. Concluí-se que a universidade é espaço aberto para o desenvolvimento e a implantação de estratégias educativas no âmbito da prevenção ao uso de tabaco.The aim was to determine the meanings attributed to tobacco consumption among freshmen college students at the University of Tegucigalpa, Honduras. A qualitative study was carried out, using symbolic interactionism as the methodological framework. We conducted four focus groups with 10 to 12 male and female students from different courses, smokers and nonsmokers. The main categories of meanings regarding tobacco use were the presence of smokers in families of origin, the spaces for the start of smoking. The reasons for the initiation of tobacco use include influence from friends and colleagues. Sports and personal commitments were considered factors that do not promote tobacco use. We concluded that the university is an open space for the development and implementation of educational strategies in the prevention against tobacco use

Moduli Spaces of Semistable Sheaves on Singular Genus One Curves

We find some equivalences of the derived category of coherent sheaves on a Gorenstein genus one curve that preserve the (semi)-stability of pure dimensional sheaves. Using them we establish new identifications between certain Simpson moduli spaces of semistable sheaves on the curve. For rank zero, the moduli spaces are symmetric powers of the curve whilst for a fixed positive rank there are only a finite number of non-isomorphic spaces. We prove similar results for the relative semistable moduli spaces on an arbitrary genus one fibration with no conditions either on the base or on the total space. For a cycle $E_N$ of projective lines, we show that the unique degree 0 stable sheaves are the line bundles having degree 0 on every irreducible component and the sheaves $\mathcal{O}(-1)$ supported on one irreducible component. We also prove that the connected component of the moduli space that contains vector bundles of rank $r$ is isomorphic to the $r$-th symmetric product of the rational curve with one node.Comment: 26 pages, 4 figures. Added the structure of the biggest component of the moduli space of sheaves of degree 0 on a cycle of projective lines. Final version; to appear en IMRS (International Mathematics Research Notices 2009

Optimum cork stopper diameter for a proper wine sealing performance when modifying bottleneck diameter: a first approach

Aim of study: This study present a theoretical model that allow establishing the proper relationship between forces and diameters that take part in sealing for ensuring an adequate closure during storage time, and obtained the optimum stopper diameter for a proper sealing performance when modifying bottleneck diameter.Area of study: The proposed model is of interested to the whole cork value chain from forest owners to natural cork stoppers manufacturers.Material and methods: The optimum cork stopper diameter depends mainly on stopper quality and the compression rate applied in the bottling operation. In this study, we establish the stopper diameter when reducing bottleneck diameter, applying a compression rate of 33% when corking, and for natural cork stoppers which quality allows to recover its initial diameter to 96% after 24 h since compression.Main results: For a bottleneck diameter of 18 mm, the value of the stopper diameter should be at least of 22.3 mm, and for a bottleneck diameter of 17 mm, the value of the stopper diameter should be at least of 20.3 mm.Research highlights: These results try to solve one of the main worries of natural cork stopper manufacturers, which is the scarcity of raw cork suitable for manufacturing them. However this study is also of interested to forest owners because the increment of cork suitable for natural cork stoppers manufacturing means an increment in cork value.Key words: bottling; corking; compression force; compression rate; diameter recovery; relaxation force; relaxation ratio.Abbreviations used: Ds (Cork Stopper Diameter); Dg (Caliper Diameter the Corking Machine); Db (Bottleneck Diameter); Dr (Recovered Diameter); Fc (Compression Force); Fr (Relaxation Force);  CR (Compression Rate); RR (Relaxation Ratio); RD (Diameter Recovery)

Últimas tendencias en sembradoras convencionales

En este artículo se van a reflejar las últimas tendencias que se están incorporando a las máquinas sembradoras para hacer frente a los desafíos que representan el mínimo laboreo, la necesidad de mayores capacidades de trabajo y el mantenimiento de un elevado nivel de precisión

Adaptación al espacio europeo de educación superior en la Diplomatura en Turismo: una experiencia piloto en la Universidad de Sevilla

E ste trabajo parte de una experiencia piloto desarrollada en las asignaturas de Dirección de Operaciones de la Diplomatura en Turismo de la Universidad de Sevilla, con objeto de iniciar el proceso de adaptación a los requerimientos de la Declaración de Bolonia ante el proyecto de creación del Espacio Europeo de Educación Superior. Esta investigación se incluye en otra de mayor alcance en la que se analiza, de forma detallada, la experiencia piloto de implantación del Sistema de Créditos Europeo (ECTS ) en tres asignaturas impartidas por las autoras de este trabajo.T his article begins with a pilot experience through the Operations Management subjects teaching in Tourism Degree in the University of Seville in order to adapt this subject to the Bolonia specifications and the creation of the European Higher Education Area. This research is part of an investigation that analyses the pilot experience of implementation of the European Credit Transfer and Acumulation System in three subjects teaching by the authors

Experiencia piloto de adaptación de las asignaturas de operaciones de la Diplomatura en Turismo de la Universidad de Sevilla al sistema ECTS

Este trabajo gira en torno a una experiencia piloto desarrollada en tres asignaturas de Dirección de Operaciones que forman parte de la Diplomatura en Turismo de la Universidad de Sevilla, con objeto de iniciar el proceso de adaptación al Sistema de Créditos Europeo (ECTS: European Credit Transfer and Accumulation System). Creemos que dicha experiencia puede ser útil a otros profesores que aún no hayan comenzado la adaptación de las asignaturas que imparten a los requerimientos para la creación del Espacio Europeo de Educación Superior (European Higher Education Area).This study deals with a pilot scheme conducted in Operations Management courses that are part of the Tourism studies at the University of Seville, with a view to initiating the process for adapting to the European Credit Transfer and Accumulation System (ECTS ). In our opinion this experience may be of use to other teachers that have still not adapted the subjects to the requirements that the creation of the European Higher Education Area entails

A Low Frequency of Losses in 11q Chromosome Is Associated with Better Outcome and Lower Rate of Genomic Mutations in Patients with Chronic Lymphocytic Leukemia

[EN] To analyze the impact of the 11q deleted (11q-) cells in CLL patients on the time to first therapy (TFT) and overall survival (OS), 2,493 patients with CLL were studied. 242 patients (9.7%) had 11q-. Fluorescence in situ hybridization (FISH) studies showed a threshold of 40% of deleted cells to be optimal for showing that clinical differences in terms of TFT and OS within 11q-CLLs. In patients with >= 40% of losses in 11q (11q-H) (74%), the median TFT was 19 months compared with 44 months in CLL patients with <40% del(11q) (11q-L) (P<0.0001). In the multivariate analysis, only the presence of 11q-L, mutated IGHV status, early Binet stage and absence of extended lymphadenopathy were associated with longer TFT. Patients with 11q-H had an OS of 90 months, while in the 11q-L group the OS was not reached (P = 0.008). The absence of splenomegaly (P = 0.02), low LDH (P = 0.018) or beta 2M (P = 0.006), and the presence of 11q-L (P = 0.003) were associated with a longer OS. In addition, to detect the presence of mutations in the ATM, TP53, NOTCH1, SF3B1, MYD88, FBXW7, XPO1 and BIRC3 genes, a select cohort of CLL patients with losses in 11q was sequenced by next-generation sequencing of amplicons. Eighty % of CLLs with 11q-showed mutations and fewer patients with low frequencies of 11q-had mutations among genes examined (50% vs 94.1%, P = 0.023). In summary, CLL patients with <40% of 11q-had a long TFT and OS that could be associated with the presence of fewer mutated genes.European Commision (EC). Funding FP7/SP1/HEALTH. Project Code: 30624