1,365,589 research outputs found
Asim Waqif: Strategies for Disruption
No full textAsim Waqif\u27s projects attempt to span architecture, art and design, with a strong contextual reference to contemporary urban design and the politics of occupying/ intervening/ using public spaces. Concerns of ecology and anthropology weave through his work, and he has done extensive research on vernacular systems of ecological management, especially with respect to water, waste and architecture. His artworks employ manual processes that are deliberately painstaking and laborious while the products themselves are temporary or even designed to decay.He has worked in sculpture, site-specific public installation, video, photography and with large-scale interactive installations that combine traditional and new media.https://digitalcommons.risd.edu/painting_kirloskarvisitingscholarlectures/1003/thumbnail.jp
A Synchronization Library for ASIM
No full textThis memo describes the functions in the synchronization library provided for programs written for ASIM and acts as a user's manual. Mul-T provides futures and binary semaphores as primitive synchronization mechanisms. For experimenting with other synchronization constructs, we have extended the language to include J-structures, L-structures, mutualexclusion locks, counting semaphores and barriers. An extension of futures to allow thread placement directives is also provided. 1 Introduction A synchronization library is provided in ASIM for users to experiment with various synchronization mechanisms. This memo assumes knowledge of programming in the ASIM environment. See Alewife Memo 13 for a description of the ASIM environment. The library contains implementations of mutual-exclusion locks, counting semaphores, Jstructures, L-structures, and barriers. These supplement the synchronization mechanisms already present in Mul-T on ASIM, viz., futures, and binary semaphores. This memo will b..
Numerical Investigations on Vortical Structures in the Near Tongue Region of a Centrifugal Pump during Transient Operation
No full textCentrifugal pumps are considered to be an integral part of process industries around the world. The flow structure within centrifugal pumps is very complex due to the interaction between the rotating impeller and the geometric features around it, such as tongue. Researchers have been analysing the effects of the interactions between impeller blades and the tongue, however, most of these studies are based on steady-state approximations where the impeller blades are modelled using frozen-rotor approach which leads to discrepancies in the predicted flow fields. In the present study, fully transient numerical investigations, on the generation and dissipation of vortical structures in the vicinity of the tongue region, have been carried out using a commercial Computational Fluid Dynamics (CFD) based solver. The instantaneous behaviour of a centrifugal pump is studied using the Sliding Mesh technique. Simulations have been carried out on both a constant rotating speed and under decelerating conditions. The second invariant of the velocity gradient tensor i.e. Q-criterion, has been employed to identify the generation and dissipation of vortical structures near the tongue region of the pump. The results indicate that the Q-criterion is fairly non-uniform downstream the tongue region due to the complex interaction between the impeller blades and the tongue. Furthermore, it has been observed that as the rotational speed of the centrifugal pump decreases, the Q-criterion in the near tongue region remains constant. The generation, expansion and subsequent mixing of two distinct vortical structures have been noticed downstream the tongue (within the volute), whereby the strength of these structures has been observed to be decreasing as the distance from the tongue increases
Optimal Design of Capsule Transporting Pipeline carrying Spherical Capsules
No full textA capsule pipeline transports material or cargo in capsules propelled by fluid flowing through a pipeline. The cargo may either be contained in capsules (such as wheat enclosed inside sealed cylindrical containers), or may itself be the capsules (such as coal compressed into the shape of a cylinder or sphere). As the concept of capsule transportation is relatively new, the capsule pipelines need to be designed optimally for commercial viability. An optimal design of such a pipeline would have minimum pressure drop due to the presence of the solid medium in the pipeline, which corresponds to minimum head loss and hence minimum pumping power required to drive the capsules and the transporting fluid. The total cost for the manufacturing and maintenance of such pipelines is yet another important variable that needs to be considered for the widespread commercial acceptance of capsule transporting pipelines. To address this, the optimisation technique presented here is based on the least-cost principle. Pressure drop relationships have been incorporated to calculate the pumping requirements for the system. The maintenance and manufacturing costs have been computed separately to analyse their effects on the optimisation process. A design example has been included to show the usage of the model presented. The results indicate that for a specific throughput, there exists an optimum diameter of the pipeline for which the total cost for the piping system is at its minimum
A simultaneous observation of lightning by ASIM, Colombia‐Lightning Mapping Array, GLM and ISS‐LIS
No full textThe Atmosphere‐Space Interactions Monitor (ASIM) on the International Space Station (ISS) provides optical radiances and images of lightning flashes in several spectral bands. This work presents a lightning flash simultaneously observed from space by ASIM, the Geostationary Lightning Mapper (GLM) and the Lightning Imaging Sensor on the International Space Station (ISS‐LIS); and from ground by the Colombia Lightning Mapping Array (Colombia‐LMA). Volumetric weather radar provides reflectivity data to help to interpret the effects of the cloud particles on the observed optical features. We found that surges in radiance in the band at 777.4 nm appear to be related mostly with lightning processes involving currents as well with branching of lightning leaders with new leader development. In cloud areas with reflectivity <18 dBZ above the lightning leader channels at altitudes >7 km, these have been imaged by ASIM and GLM. But in the region with reflectivity <23 dBZ, despite its lower cloud tops and similar altitudes of lightning channels, these have been almost undetectable. The calculated relative optical depths are consistent with the observed optical intensity at the cloud top. Despite the effects of the cloud particles and the altitude of the lightning channels on the attenuation of the luminosity, the luminosity of the lightning channels due to different processes is fundamental for the imaging of lightning from space
Pressure Drop in Capsule Transporting Bends Carrying Spherical Capsules
No full textOne of the most important parameters in designing a capsule transporting pipeline is the pressure drop in the pipes carrying capsules and associated pipe fittings such as bends etc. Capsules are hollow containers with typically cylindrical or spherical shapes flowing in the pipeline along with the carrier fluid. The dynamic behavior of a long train of capsules depends on the behavior of each capsule in the train and the hydrodynamic influence of one capsule on another. Researchers so far have used rather simplified empirical and semi-empirical correlations for pressure drop calculations, the range and application of which are fairly limited. Computational Fluid Dynamics (CFD) based techniques have been used to analyze the effect of the presence of solid phase in hydraulic bends. A steady state numerical solution has been obtained from the equations governing turbulent flow in pipe bends carrying spherical capsule train consisting of one to four capsules. The bends under consideration are of 45⁰ and 90⁰ with an inner diameter of 0.1m. The investigation was carried out in the practical range of 0.2 ≤Vb≥ 1.6 m/sec. The computationally obtained data set over a wide range of flow conditions has been used to develop a rigorous model for pressure drop calculations. The pressure drop along the pipe bends, in combination with the pressure drop along the pipes, can be used to calculate the pumping requirements and hence design of the system
Optimisation of a Horizontal Capsule Transporting Pipeline carrying Cylindrical Capsules
No full textPipelines carrying fluids and slurries are quite common. The third-generation pipelines carrying spherical or cylindrical capsules (hollow containers) filled with minerals or other materials including hazardous liquids are rather a new concept. These pipelines need to be designed optimally for commercial viability. An optimal design of such a pipeline results in minimum pressure drop in the pipeline. This corresponds to minimum head loss and hence minimum pumping power required to drive the capsules and the transporting fluid. This study uses a rigorous approach to predict pumping cost based on Computational Fluid Dynamics (CFD) and hence optimize the design of the capsule transporting pipelines. Pressure drop relationship developed has been incorporated to calculate the pumping requirements for the system. Based on the least-cost principle, a methodology has been developed for the determination of the optimal diameter of cylindrical capsule carrying hydraulic pipeline. This procedure can be applied to obtain the optimal size of the capsule pipeline for minimum pumping and capital costs
First ten months of TGF observations by ASIM
No full textThe Atmosphere-Space Interactions Monitor (ASIM) was launched to the International Space Station (ISS) on April 2, 2018. The ASIM payload consists of two main instruments, the Modular X- and Gamma-ray Sensor (MXGS) for imaging and spectral analysis of Terrestrial Gamma-ray Flashes (TGFs) and the Modular Multi-spectral Imaging Array (MMIA) for detection, imaging and spectral analysis of Transient Luminous Events (TLEs) and lightning. ASIM is the first space mission designed for simultaneous observations of TLEs, TGFs and optical lightning. During the first ten months of operation (June 2, 2018 to April 1, 2019) the MXGS has observed 217 TGFs. In this paper we report several unprecedented measurements and new scientific results obtained by ASIM during this period: 1) simultaneous TGF observations by Fermi Gamma-ray Burst Monitor (GBM) and ASIM MXGS revealing the very good detection capability of ASIM MXGS and showing substructures in the TGF, 2) TGFs and Elves produced during the same lightning flash and even simultaneously have been observed, 3) first imaging of TGFs giving a unique source location, 4) strong statistical support for TGFs being produced during the upward propagation of a leader just before a large current pulse heats up the channel and emits a strong optical pulse, and 5) the t50 duration of TGFs observed from space is shorter than previously reported
Relocation of the Atmosphere-Space Interactions Monitor (ASIM) on the International Space Station
No full textThe Atmosphere-Space Interactions Monitor (ASIM) is a 314-kilogram external payload attached to the Columbus module of the International Space Station (ISS). It was developed by the European Space Agency (ESA) and the main objective of ASIM is the study of the upper layers of the atmosphere and in particular, phenomena known as Transient Luminous Events and Terrestrial Gamma-ray Flashes. On board since April 2018, ASIM has produced outstanding science. ASIM mission was supposed to end in December 2021 when another payload was programmed to use its location. With its excellent health and science output, the idea was put forward to relocate ASIM somewhere else on the station instead of simply removing and trashing it. With very little lead time, the ground teams managed to overcome all the hurdles to make this relocation possible. From a nadir viewing payload, designed to monitor the top of thunderstorms, ASIM has become a limb viewing one since January 2022. Remarkably, a limb viewing instrument was in the original plans for ASIM, but was descoped for financial reasons. The science produced at this new location is therefore quite complementary to the original location
The ASIM Mission -- A Contamination Control and Thermal Approach
No full textCathal Mooney, ESAJan Persson, ESADan D.V. Bhanderi, TermaMatteo Tacconi, ESAOle Mikkelsen, TermaPeter Davidsen, TermaOle Hartnack, TermaICES206: Crewed Orbiting Infrastructures, Habitats, Space Station and Payload Thermal ControlThe 50th International Conference on Environmental Systems was held virtually on 12 July 2021 through 14 July 2021.The Atmosphere-Space Interactions Monitor (ASIM) is a European Space Agency (ESA) payload developed by the ASIM industrial consortium with Terma A/S, Denmark, as prime contractor. ASIM is mounted on the exterior of the European Columbus laboratory module on the International Space Station. Launched in April 2018 on the Space-X CRS-14 this external payload is a collection of optical cameras, photometers and an X- and gamma-ray detector designed to look for electrical discharges born in stormy weather conditions that extend above thunderstorms into the upper atmosphere.
Now almost three years into nominal operations, ASIM is continuously collecting data which researchers utilise for investigation of the relationship between terrestrial gamma-ray bursts, lightning and high-altitude electric discharges across all seasons, different latitudes and different times of day and night. As part of this successful operation many new design concepts and materials choices were implemented for ASIM in order to mitigate against phenomena such as cross contamination, inorbit debris and plume due to the sensitive nature of optical sensors and radiator surfaces. There is also the need to comply with non-scientific ISS external contamination and deposition requirements during the intended operational phase.
This paper will give an overview of the ASIM mission, a brief description of the instruments and focus on the cleanliness and contamination approach , implementation of bake-out and outgassing strategies and preconditioning, contamination budgets and cleanliness mitigations during AIT as well as the use of cleanliness mitigation concepts in the design, such as decontamination heaters on sensitive optics, venting design and dust caps to protect sensitive surfaces. External ISS requirements must also be met, hence an overview of the ASIM thermal design control will be presented to consolidate and substantiate the cleanliness approach. Real in-orbit data from the mission are presented showing how contamination has affected or not its performance
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