MPD work at MIT

MPD work at MIT is presented in the form of the view-graphs. The following subject areas are covered: the MIT program, its goals, achievements, and roadblocks; quasi one-dimensional modeling; two-dimensional modeling - transport effects and Hall effect; microscopic instabilities in MPD flows and modified two stream instability; electrothermal stability theory; separation of onset and anode depletion; exit plane spectroscopic measurements; phenomena of onset as performance limiter; explanations of onset; geometry effects on onset; onset at full ionization and its consequences; relationship to anode depletion; summary on self-field MPD; applied field MPD - the logical growth path; the case for AF; the challenges of AF MPD; and recommendations

Gobierno local abierto: diagnóstico en México y Oaxaca

Con un enfoque centrado en el ciudadano y el uso de las tecnologías de la información y la comunicación, la expresión gobierno abierto ha revolucionado la administración pública. Esto ha implicado una alta deliberación, colaboración, participación y publicidad. El objetivo del presente artículo es diagnosticar los estados cuyos municipios siguen el proyecto de gobierno abierto, para lo cual se tomó como muestra a los estados de México y Oaxaca, donde se compararon los estratos de desarrollo humano muy alto y bajo. A partir de ello se formuló la hipótesis de que los gobiernos locales en México responden de forma diferente a la expresión gobierno abierto cuando este tiene que ver de manera directa y proporcional con el desarrollo humano. Es decir, los municipios con mayor desarrollo humano tuvieron también mayor nivel de gobierno abierto, mientras que los gobiernos con menor desarrollo humano alcanzaron niveles inferiores de gobierno abierto. Se estudiaron 30 municipios de ambas entidades, con diez variables a analizar mediante contraste estadístico de chi cuadrada y coeficiente de correlación r de Pearson. Los resultados demostraron que sí existe una relación entre desarrollo humano y gobierno abierto

Blade scale effects of tip leakage

October 1990Includes bibliographical references (leaves 43-44)The effects of blade-tip leakage in a turbine are investigated by modeling the stage as an incomplete actuator disk. It is found that the spanwise flow redistribution due to the gap is such as to produce a uniform unloading of the blades, despite the very concentrated leakage. Partial lift retention at the blade tip is accounted for based on a leakage jet-free stream collision model which successfully predicts the roll-up of the leakage flow. The predicted efficiency loss due to the gap correlates well with experimental data

Rotordynamic forces in labyrinth seals: Theory and experiment

A theoretical and experimental investigation of the aerodynamic forces generated by a single gland labyrinth seal executing a simultaneous spinning/whirling motion has been conducted. A lumped parameter model for a single gland seal with coupling to an upstream cavity with leakage is developed along with an appropriate solution technique. From this theory, it is shown that the presence of the upstream cavity can, in some cases, augment the cross-stiffness and direct damping by a factor of four. The parameters that govern the coupling are presented along with predictions on their influence. A simple uncoupled model is used to identify the mechanisms responsible for cross force generation. This reduced system is nondimensionalized and the physical significance of the reduced parameters is discussed. Closed form algebraic formulas are given for some simple limiting cases. It is also shown that the total cross-force predicted by the uncoupled model can be represented as the sum of an ideal component due to an inviscid flow with entry swirl and a viscous part due to the change in swirl created by friction inside the gland. The frequency dependent ideal part is solely responsible for the rotordynamic direct damping. The facility designed and built to measure these frequency dependent forces is described. Experimental data confirm the validity and usefulness of this ideal/viscous decomposition. A method for calculating the damping coefficients based on the force decomposition using only the static measurements is presented. Experimental results supporting the predicted cross force augmentation due to the effect of upstream coupling are presented

Proyecto Básico de acondicionamiento de la N-332 entre el PK 192 y el PK 195 en el término municipal de Pedreguer (Alicante)

[EN] This basic refurbishment project is located on the national road N-332 at the level of the Municipality of Pedreguer in Alicante. The objective of this basic project is to carry out a refurbishment of the national road N-332, where it has been seen the need to improve the access of this road with the construction of two new service roads and a roundabout. The purpose of this conditioning is to improve the current consistency of the N-332 , since after a detailed analysis it has been discovered that it presents a very unstable traffic, In addition to this it is added the dangerous accesses that are in it, not guaranteeing the safety of the road users. For the implementation of these service routes it was necessary to carry out new drainage works for the national N-332, since those currently available could not accommodate the estimated project flows, In this way an improvement is made. This upgrading has improved the consistency and safety of road users by providing adequate accessibility to neighbouring municipalities and infrastructure.[CA] Aquest projecte bàsic de condicionament se situa en la carretera nacional N-332 a l'altura del Municipi de Pedreguer a Alacant. L'objectiu d'aquest projecte bàsic és realitzar un condicionament de la carretera nacional N-332, on s'ha vist la necessitat de millorar els accessos d'aquesta via amb la construcció de dues noves vies de servei i una glorieta. La fi d'aquest condicionament és la millora de la consistència actual de la N-332 , ja que després de realitzar una anàlisi detallada s'ha descobert que presenta un trànsit molt inestable, a més a això se li suma els perillós accessos que es troben en ella, no garantint la seguretat dels usuaris de la carretera. Per a la implantació d'aquestes vies de servei s'ha vist necessari realitzar unes noves obres de drenatge per a la nacional N-332, ja que les que hi ha en l'actualitat no podien albergar els cabals de projecte calculats, d'aquesta manera es realitza una millora d'aquesta. Amb aquest condicionament s'ha millorat la consistència i la seguretat dels usuaris de la carretera donant una accessibilitat adequada als municipis i infraestructures confrontants confrontants.[ES] Este proyecto básico de acondicionamiento se sitúa en la carretera nacional N-332 a la altura del Municipio de Pedreguer en Alicante. El objetivo de este proyecto básico es realizar un acondicionamiento de la carretera nacional N-332, donde se ha visto la necesidad de mejorar los accesos de dicha vía con la construcción de dos nuevas vías de servicio y una glorieta. El fin de este acondicionamiento es la mejora de la consistencia actual de la N-332 , ya que tras realizar un análisis detallado se ha descubierto que presenta un tráfico muy inestable, además a esto se le suma los peligroso accesos que se encuentran en ella, no garantizando la seguridad de los usuarios de la carretera. Para la implantación de estas vías de servicio se ha visto necesario realizar unas nuevas obras de drenaje para la nacional N-332, ya que las que hay en la actualidad no podían albergar los caudales de proyecto calculados, de esta manera se realiza una mejora de la misma. Con este acondicionamiento se ha mejorado la consistencia y la seguridad de los usuarios de la carretera dando una accesibilidad adecuada a los municipios e infraestructuras colindantes colindantes.Martinez Sanchez, M. (2019). Proyecto Básico de acondicionamiento de la N-332 entre el PK 192 y el PK 195 en el término municipal de Pedreguer (Alicante). http://hdl.handle.net/10251/126464Archivo delegad

Use of emission spectroscopy for real-time assessment of relative wall erosion rate of BHT-200 hall thruster for various regimes of operation

Radiation emission due to Boron atoms sputtered from the Boron-Nitride ceramic walls of a BHT-200 Hall thruster was measured as a diagnostic for real time assessment of thruster wall erosion and to determine the e ects of various operation conditions on thruster lifetime. Boron neutral 249.677 and 249.773nm lines were measured using a high resolution spectrometer. Spectral measurement results and the accompanying analysis and discussion are presented in this study. From the spectral measurements it was observed that the Boron emission intensity significantly increases for increased discharge voltage pointing to a large increase in the thruster wall erosion rate. Additionally, the measurements show that for the nominal discharge voltage and the applied magnetic field intensity, there is an optimum propellant flow rate for minimum Boron emission, thus minimum wall erosion rate. The variation in the current to the magnet coils showed that the Boron emission intensity increases for increased magnetic field and the Boron emission intensity shows similar behavior to that of the Xenon single ion emission line intensity at 248.911nm. The findings of the study show that emission spectroscopy can be used in determining the optimum operational parameters for minimum wall erosion for SPT type Hall thrusters

Variation of the ultraviolet extinction law across the Taurus-Auriga star forming complex. A GALEX based study

The Taurus-Auriga molecular complex (TMC) is the main laboratory for the study of low mass star formation. The density and properties of interstellar dust are expected to vary across the TMC. These variations trace important processes such as dust nucleation or the magnetic field coupling with the cloud. In this article, we show how the combination of near ultraviolet (NUV) and infrared (IR) photometry can be used to derive the strength of the 2175 \AA\ bump and thus any enhancement in the abundance of small dust grains and PAHs in the dust grains size distribution. This technique is applied to the envelope of the TMC, mapped by the GALEX All Sky Survey (AIS). UV and IR photometric data have been retrieved from the GALEX-AIS and the 2MASS catalogues. NUV and K-band star counts have been used to identify the areas in the cloud envelope where the 2175 \AA\ bump is weaker than in the diffuse ISM namely, the low column density extensions of L1495, L1498 and L1524 in Taurus, L1545, L1548, L1519, L1513 in Auriga and L1482-83 in the California region. This finding agrees with previous results on dust evolution derived from Spitzer data and suggests that dust grains begin to decouple from the environmental galactic magnetic field already in the envelope.Comment: Accepted in Monthly Notices of the Royal Astronomical Societ

Localized pulsed nanosecond discharges in a counterflow nonpremixed flame environment

A flame is a very unusual environment for the development of a gas discharge, since it presents strong gradients in temperature, composition, and pre-ionization. In this paper we examine how such an environment impacts the development of the plasma when using repetitive pulsed nanosecond discharges, one of the main strategies used in the field of plasma assisted combustion. Experiments were performed in a counterflow nonpremixed burner with parallel electrodes at the nozzle exits and nanosecond-resolved photography of the plasma emission is presented. It was shown that the discharge development in stratified media may take place in the form of a dielectric barrier discharge with a localized energy deposition. In the experiments presented the discharge energy was coupled to the flame front because of the high rate of chemi-ionization and the gas density decrease in the flame

The ferroelectric Mott-Hubbard phase of organic (TMTTF)2X conductors

We present experimental evidences for a ferro-electric transition in the family of quasi one- dimensional conductors (TMTTF)2X. We interpret this new transition in the frame of the combined Mott-Hubbard state taking into account the double action of the spontaneous charge disproportionation on the TMTTF molecular stacks and of the X anionic potentials