Low power arcjet thruster pulse ignition

An investigation of the pulse ignition characteristics of a 1 kW class arcjet using an inductive energy storage pulse generator with a pulse width modulated power converter identified several thruster and pulse generator parameters that influence breakdown voltage including pulse generator rate of voltage rise. This work was conducted with an arcjet tested on hydrogen-nitrogen gas mixtures to simulate fully decomposed hydrazine. Over all ranges of thruster and pulser parameters investigated, the mean breakdown voltages varied from 1.4 to 2.7 kV. Ignition tests at elevated thruster temperatures under certain conditions revealed occasional breakdowns to thruster voltages higher than the power converter output voltage. These post breakdown discharges sometimes failed to transition to the lower voltage arc discharge mode and the thruster would not ignite. Under the same conditions, a transition to the arc mode would occur for a subsequent pulse and the thruster would ignite. An automated 11 600 cycle starting and transition to steady state test demonstrated ignition on the first pulse and required application of a second pulse only two times to initiate breakdown

Low power arcjet performance

An experimental investigation was performed to evaluate arc jet operation at low power. A standard, 1 kW, constricted arc jet was run using nozzles with three different constrictor diameters. Each nozzle was run over a range of current and mass flow rates to explore stability and performance in the low power engine. A standard pulse-width modulated power processor was modified to accommodate the high operating voltages required under certain conditions. Stable, reliable operation at power levels below 0.5 kW was obtained at efficiencies between 30 and 40 percent. The operating range was found to be somewhat dependent on constrictor geometry at low mass flow rates. Quasi-periodic voltage fluctuations were observed at the low power end of the operating envelope, The nozzle insert geometry was found to have little effect on the performance of the device. The observed performance levels show that specific impulse levels above 350 seconds can be obtained at the 0.5 kW power level

Investigation of electrical noise in selenium-immersed thermistor bolometers

The selenium immersed, thermistor bolometer, IR detector failed due to spurious and escalating electrical noise outburst as a function of time at elevated temperatures during routine ground based testing in a space simulated environment. Spectrographic analysis of failed bolometers revealed selenium pure zones in the insulating selenium arsenic (Se-As) glass film which surrounds the active sintered Mn, Ni, Co oxide flake. The selenium pure film was identified as a potentially serious failure mechanism. Significant changes were instituted in the manufacturing techniques along with more stringent process controls which eliminated the selenium pure film and successfully produced 22study bolometers

Intercultural Contributions to Mission Education

https://place.asburyseminary.edu/firstfruitspapers/1151/thumbnail.jp

En los límites del Estado de Derecho: un análisis de la justicia administrativa

Divulgação dos SUMÁRIOS das obras recentemente incorporadas ao acervo da Biblioteca Ministro Oscar Saraiva do STJ. Em respeito à lei de Direitos Autorais, não disponibilizamos a obra na íntegra.Localização na estante: 342.2(460) S246

Población y Desarrollo: Objeto de reflexión Bioética

Según el último informe de Naciones Unidas sobre población mundial, se estima que la población aumentará hasta 9.3 mil millones en 2050 y a 10.1 mil millones en 2100.1 Tal crecimiento, que pudiera parecer exagerado, no lo es por muchas razones, especialmente si se mira la trasformación que ha vivido el globo en los últimos 30 años en relación con la tasa de fecundidad

Towards a Semantic Gas Source Localization under Uncertainty

Towards a Semantic Gas Source Localization under Uncertainty.Communications in Computer and Information Science book series (CCIS, volume 855), doi:10.1007/978-3-319-91479-4_42This work addresses the problem of efficiently and coherently locating a gas source in a domestic environment with a mobile robot, meaning efficiently the coverage of the shortest distance as possible and coherently the consideration of different gas sources explaining the gas presence. The main contribution is the exploitation, for the first time, of semantic relationships between the gases detected and the objects present in the environment to face this challenging issue. Our proposal also takes into account both the uncertainty inherent in the gas classification and object recognition processes. These uncertainties are combined through a probabilistic Bayesian framework to provide a priority-ordered list of (previously observed) objects to check. Moreover the proximity of the different candidates to the current robot location is also considered by a cost function, which output is used for planning the robot inspection path. We have conducted an initial demonstration of the suitability of our gas source localization approach by simulating this task within domestic environments for a variable number of objects, and comparing it with an greedy approach.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

‘Crafting Conductive Circuits and Capacitive Surfaces in Glass’. Making Futures Vol. 5., Plymouth: Plymouth College of Art. ISSN 2042-1664

Engaging the theme of Curating Maker Cultures, thais presentation features methods and processes used in the development of conductive circuits in handcrafted glass and copper combined with interactive sensors. It will also include a display of resulting objects, which have been created in a series of cross-disciplinary workshops that demonstrate the exposure of existing potentials for combining artisanal glassmaking with digital manufacture and interactive electronics. For over a decade, National Glass Centre Research at the University of Sunderland has developing digital making in a material that has a long history of making by hand. In particular it has pioneered the creative use of waterjet cutting in glass, and has pursued a shift toward digital craft in its curriculum. This project, however, seeks to consider continuity in craft as a way of thinking rather than as distinct areas of practice and encouraging new and best practice using both digital and manual making. This collaboration with the Craft Futures research group at Northumbria University and their combined Centre for Doctoral Training involves academic and student researchers from both universities as well as Newcastle University’s OpenLab. The project seeks to provide a demonstration of a new area of thinking in which the combined skills of makers drives forward new opportunities of forms of interaction with crafted objects and for traditional craftspeople to form a connection with digital possibilities in creative work. While there are many coders and potentials for interactions, the exploration of handcrafted glass and copper constructions offer new possibilities for interfaces. Glass is a material that can be formed through skillful blowing, casting, cutting and kilnforming. It adds potential uses of colour, transparency, weight and potential for optical effects. Combined with sensors a myriad of effects can be achieved. So far the workshops have yielded experiments in 3-dimensional circuits through integrating glass with a conductive material. Copper, a compatible material, has been embedded within melted glass to create an interface for an LED ‘light-writer’ that can produce a range of RGB colours transmitted through the glass surfaces. A colour sensor is being developed to compare synthetic light to objects in coloured glass. Contoured air pockets have been waterjet cut and trapped within solid glass blocks to create circuits using solid or liquid conductive materials. Screenprinting techniques are being used to create ornamental circuitry within glass tiles. Copper wire cages form ‘electric veins’ that constrict unique blown glass vessels. The project is ongoing and it is anticipated that objects can be demonstrated at Making Futures. This study is an exploration of materiality and the creation of artefacts as meaningful moments in art, craft and design. By working with researchers with a broad range of craft specialisms, we are using this collaboration to rethink the partnership of materials

Harvesting Thermal Fluctuations: Activation Process Induced by a Nonlinear Chain in Thermal Equilibrium

We present a model in which the immediate environment of a bistable system is a molecular chain which in turn is connected to a thermal environment of the Langevin form. The molecular chain consists of masses connected by harmonic or by anharmonic springs. The distribution, intensity, and mobility of thermal fluctuations in these chains is strongly dependent on the nature of the springs and leads to different transition dynamics for the activated process. Thus, all else (temperature, damping, coupling parameters between the chain and the bistable system) being the same, the hard chain may provide an environment described as diffusion-limited and more effective in the activation process, while the soft chain may provide an environment described as energy-limited and less effective. The importance of a detailed understanding of the thermal environment toward the understanding of the activation process itself is thus highlighted

High-cadence spectroscopy of M-dwarfs – II. Searching for stellar pulsations with HARPS

Stellar oscillations appear all across the Hertzsprung–Russell diagram. Recent theoretical studies support their existence also in the atmosphere of M dwarfs. These studies predict for them short periodicities ranging from 20 min to 3 h. Our Cool Tiny Beats (CTB) programme aims at finding these oscillations for the very first time. With this goal, CTB explores the short time domain of M dwarfs using radial velocity data from the High Accuracy Radial velocity Planet Searcher (HARPS)-European Southern Observatory and HARPS-N high-precision spectrographs. Here we present the results for the two most long-term stable targets observed to date with CTB, GJ 588 and GJ 699 (i.e. Barnard's star). In the first part of this work we detail the correction of several instrumental effects. These corrections are especially relevant when searching for subnight signals. Results show no significant signals in the range where M dwarfs pulsations were predicted. However, we estimate that stellar pulsations with amplitudes larger than ∼0.5 m s−1 can be detected with a 90 per cent completeness with our observations. This result, along with the excess of power regions detected in the periodograms, opens the possibility of non-resolved very low amplitude pulsation signals. Next generation more precise instrumentation would be required to detect such oscillations. However, the possibility of detecting pulsating M-dwarf stars with larger amplitudes is feasible due to the short size of the analysed sample. This motivates the need for completeness of the CTB survey