1,721,490 research outputs found
Dataset supporting the Southampton doctoral thesis: Development and characterisation of an additive manufactured high-temperature resistojet
No full textThis dataset contains life testing data and thrust data generated in experiments </span
Dataset for: Endurance testing of STAR resistojet
No full textDataset supports: 'Endurance testing of the additively manufactured STAR resistojet' published in Materials & Design.
This dataset contains .csv files produced during endurance testing of two stainless steel 316L prototype resistojet thruster assemblies. The files are automatically created by a LabVIEW GUI that controls the experiments, and include readings from thermocouples, the thruster power supply, and current and voltage measurements. The file includes measurements related to propellant and thrust which are not populated here as they were not used for these endurance tests. </span
Water management technology for implementing a water culture for bus operators
Full text linkTransit operators’ concerns about water as a resource are minimal. No standards and policies to manage water in washing operations are available, which are accomplished according to local practice. This paper moves from here and presents a cost-benefit scenario assessment, where an innovative water reclamation and harvesting technology, for the bus sector, is applied to washing operations within the European Commission’s LIFEH2OBUS project. The theoretical approach behind (coherent with consolidated methodologies applied in transportation studies developed within past European research projects) is to assess performance trends and impacts (associated with several evaluation categories such as society, environment, operations, and energy) by scenario building and via cost-benefit and sensitivity analyses, also including the design of performance threshold to successfully implement the innovative technology outside the LIFEH2OBUS project. The scenario highlights a 92% reduction in water consumption after one year of implementation, i.e., 21,528,000 liters saved for a fleet of 500 buses. By reaching 50% of the European transit fleet in 5 years (342,143 buses), 14,731,309,008 liters/year can be saved, along with a 29 GWh/year reduction of energy consumption and 74 ktCO2eq/year fewer greenhouse gas emissions. The research goal is to evidence water saving potential and pioneer a new study field on water management, thus launching a new “Water Culture” among bus operators
Development and characterisation of an additive manufactured high-temperature resistojet.
No full textThe increasing capabilities of small satellites, and the transitioning of geostationary satellites to electric propulsion, are driving a demand for low-cost propulsion systems operating at low power and high thrust. Resistojets are an attractive technology to meet this demand, with high thrust-to-power ratio, simple construction, and compatibility with a wide range of propellants for integration into all-electric propulsion architectures. However, currently available resistojets operate at very low specific impulse, and their use is therefore limited. This can be improved by operating at higher temperatures, but there are many challenges associated with doing so. These include withstanding cyclic thermal stresses, counteracting increased inefficiency due to heat loss, and manufacturing difficulties associated with high-temperature materials. Advances in additive manufacturing technologies can help to overcome these challenges, enabling the production of complex heater geometries at low cost. The combination of industry demand and new manufacturing capabilities makes investigation of high-temperature resistojets timely.In the first part of this thesis, a previously developed proof-of-concept additive manufactured resistojet was tested to determine its endurance to thermal cycling representative of its operational conditions. Two premature failure modes were discovered through this experimental campaign using electrical diagnostics during testing. X-ray computed tomography imaging was used to non-destructively inspect the prototypes after testing, and the resulting images were combined with the in-situ data to determine the failure mechanisms. 3D numerical models incorporating coupled electrical, thermal and mechanical physics were used to investigate the temperature and stress distributions in the prototypes. The experimental and numerical approaches provided complementary insights into the complex behaviour of the resistojet, which includes operation of materials close to their melting points, and highly non-linear phenomena such as radiative heat transfer. Using these approaches, the design was updated to eliminate the identified failure modes by reducing the buildup of thermal stresses from differential thermal expansion. The new design was manufactured in the nickel alloys Inconel 718 and Hastelloy X, as well as in the refractory metal tantalum. An experimental campaign on the new design, the first to be reported in candidate flight materials for the high-temperature resistojet, showed an order of magnitude improvement in endurance, but failed to meet the requirements. The updated design was demountable, allowing visual inspection of the failure sites after testing. Numerical modelling indicated that the approach to thermal stress reduction was promising, and provided directions for further improvement.The second part of this thesis presented a second design iteration, manufactured using Inconel 625 and tantalum. Endurance tests showed for the first time that additive manufactured high-temperature resistojet heaters and engineering model thrusters could exceed the required cycle life for industrial application. Numerical models showed that this extended endurance was due to reduction of thermal stress, as a result of a design which matched the thermal expansion of different components. The performance of these thrusters was characterised by direct thrust measurements in vacuum. The Inconel 625 thruster achieved a maximum specific impulse with xenon of 61.6 +/- 0.6 s, at a thrust of 89 +/- 0.4 mN, using 3 bar supply pressure and 58 +/-$0.6 W input power. The thrust-to-power ratio in this test was 1.5 mN/W. Varying supply pressure from 2 to 4 bar at 58 W increased the thrust by a factor of 2 while maintaining >95 % of the maximum measured specific impulse. The tantalum thruster achieved a maximum specific impulse measured with argon of 120.6 +/- 0.9 s specific impulse at a thrust of 189.0 +/- 0.6 mN, using 7 bar supply pressure and 180 +/- 1.1 W input power. This performance implies a specific impulse of 66 s with xenon. These values exceed the specific impulse of commercial state-of-the-art resistojets by 28 % (Inconel 625) and 37 % (tantalum). The work presented in this thesis advances the field of propulsion by demonstrating, for the first time, that engineering model additive manufactured resistojets made from high-temperature materials can withstand cyclic operation for mission-relevant timescales; by directly measuring significantly greater specific impulse than that provided by the state of the art; and by developing combined numerical and experimental methods for analysing the thrusters, which can be used in future design efforts. This work has raised the technology readiness level of high-temperature additive manufactured resistojets from 3 to 5. It has demonstrated the potential of resistojets to address the identified needs of the space industry, and identified paths to develop further to a viable propulsion system
Water as a pivotal resource for the environmentally conscious management of bus fleets in Europe
No full textThere is not much interest in the transport sector, specifically among transit operators, on the potential achievable from improving water management as consolidated garage practice. Bus washing operations are highly water and energy-demanding, but this seems to go unnoticed, being operators' primary concern on pollution and energy. However, proper water management can improve the sustainability of the transit fleets, as the European Commission's LIFEH2OBUS project is slated to demonstrate. The paper describes the water-saving technologies to be tested in the project, i.e., water reclamation; water reclamation and harvesting; waxing without water, and provides tangible, quantitative facts on reducing water consumption when washing buses in terms of water, energy and monetary savings, according to a cost-benefit analysis simulating the implementation of the three technologies in three different bus garages in Europe. All of the above, with the research goal to launch a new “Water Culture” among transit operators and advance scientific knowledge further afield
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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