1,738,189 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..
Optimal Design of Capsule Transporting Pipeline carrying Spherical Capsules
Get PDFA 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
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
Pressure Drop in Capsule Transporting Bends Carrying Spherical Capsules
Get PDFOne 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
ASIM-Workshop STS/GMMS 2014 : Treffen der ASIM/GI-Fachgruppen "Simulation technischer Systeme" und "Grundlagen und Methoden in Modellbildung und Simulation", 20. bis 21. Februar 2014 in Reutlingen-Rommelsbach
No full textMit der Verfügbarkeit leistungsfähiger Computer haben rechnergestützte Simulationsverfahren überall in Wissenschaft und Technik Einzug gehalten. Die modellbasierte Simulation als "virtuelles Experiment" stellt insbesondere im Entwurf technischer Systeme ein wirksames und längst unverzichtbares Hilfsmittel dar, um Entwicklungsergebnisse hinsichtlich gewünschter Eigenschaften abzusichern. Die Möglichkeiten heutiger Simulationsmethoden sind faszinierend, weshalb gerade Anfänger (aber nicht nur diese) der Gefahr ausgesetzt sind, deren Ergebnisse unkritisch zu übernehmen. Besondere Bedeutung kommt hier der Lehre zu. Neben der Anwendung der Simulationswerkzeuge ist es wichtig, den Studierenden auch deren theoretische Grundlagen nahe zu bringen und damit ihr Bewusstsein hinsichtlich der Grenzen der Simulation zu schärfen. Der Workshop der ASIM/GI-Fachgruppen "Simulation technischer Systeme" und "Grundlagen und Methoden in Modellbildung und Simulation" bringt Fachleute aus Wirtschaft und Wissenschaft zum Erfahrungsaustausch rund um die Simulation zusammen. Hierbei werden alle Aspekte von den Grundlagen über die Methoden bis hin zu Werkzeugen und Anwendungsbeispielen angesprochen
Asim, een groot man en een voorbeeld voor ons allen
No full textAsim: een groot man en een voorbeeld voor ons allen Radeloos kwam hij op mijn spreekuur, 45 jaar oud. Met een vriend om hem bij te staan. Hij had pijn in zijn rug en been. Hij sprak goed Nederlands. Syriër, hoog opgeleid, prachtige functie. Maar door zijn pijn had hij moeten stoppen met werken, kwam in de ziektewet, raakte hij zijn baan kwijt. Helaas bleef het daar niet bij. De relatie met zijn echtgenote leed er fors onder en hun huwelijk overleefde het niet. Zijn enige kind zag hij nauwelijks meer. En zijn trots…. Hij was alles kwijt. Asim had een uitgebreide voorgeschiedenis met veel maag- en darmklachten, operaties, pijn en de daarbij behorende pijnstilling. Hij gebruikte sterke pijnstilling waar hij zweterig van werd, hij kon zijn handen niet meer bewegen en was "bijna in coma" geweest. Zo…. niet niks! Vijf jaar geleden was Asim vanwege een endeldarmtumor geopereerd. De tumor was weg, maar met de nabestraling en chemokuren erbij was hij met pijn in bekken en been uit deze periode gekomen. De vriend die hem vergezelde was een uit Syrië afkomstige gepensioneerde kinderarts. Hij was meegekomen om te luisteren en bijstand te verlenen. Want Asim sukkelde alsmaar door en het ging steeds slechter. Ook de voorgaande pijnbehandelingen elders waren niet succesvol geweest, lichtte zijn vriend toe, niemand kreeg hem beter. Het duurde allemaal lang en Asim wilde weer verder met zijn leven. De pijn was sterk verergerd sinds een half jaar. Diverse scans waren zojuist door een collega gemaakt. Ik besprak met Asim wat de vermoedelijke pijndiagnose was op basis van alle beschikbare gegevens en wilde de resultaten van het laatste onderzoek er graag bij betrekken. Maar Asim was met de verwachting gekomen, na de lange tijd van ernstig lijden, dat ik hem nu wel direct van de pijn zou afhelpen. Ik was geraakt door zijn lijden en frustratie, vanwege zijn gevoel dat alles hem ontglipte. Woedend werd Asim, toen ik hem niet kon beloven de pijn meteen weg te kunnen nemen. Samen met de vriend kreeg ik Asim rustig. Ik voelde me er niet comfortabel bij, maar ik voelde wel mee met Asim. We spraken een begeleidingstraject af met pijnbehandeling, revalidatie en psychosociale begeleiding. Het ging op en af. De blaasproblemen bleven terugkeren en leidden tot opnames in het ziekenhuis. We kregen de pijn in anus en been redelijk onder controle, maar daarvoor in de plaats kwam pijn in de blaasstreek. We hebben dat enigszins kunnen verminderen met een pijnbehandeling, maar de vechtlust van Asim nam met de dag af. Hij begon te berusten. Asim was Koptisch christen en vond dat hij zijn pijn en lijden moest dragen. Dat gaf zijn geloof in. Daarom wilde hij geen spinaal katheter. Groots was zijn draagkracht en zó onverwacht vergeleken met hoe hij over kwam tijdens onze eerste ontmoetingen. Dit had ik nooit verwacht. Regelmatig liep ik even bij hem langs als ik hoorde dat hij weer opgenomen was. Dat heeft zo een paar maanden geduurd. Wij hoefden niet veel meer te veranderen aan het pijnbeleid. “Fijn dat u er bent, dokter. Maar het is goed zo….”. In de zomer van afgelopen jaar was zijn laatste opname. Met thuiszorg is Asim thuis overleden, onder familie en vrienden. Als arts maak ik vele patiënten mee in hun lijdensweg. Wat me zo raakte in Asim was zijn vurigheid en vechtlust, die hij met zijn geloof wist om te zetten in een ongelofelijke kracht om zijn lijden te dragen. Asim liet ons in extremen zijn lijden, kracht en menselijkheid zien, om al zijn verliezen om te zetten in een verdraagzaamheid en acceptatie. Asim was een groot man en een voorbeeld voor ons allen. André P. Wolff, Hoogleraar Anesthesiologie i.h.b. Pijngeneeskunde, Pijncentrum UMC
First ten months of TGF observations by ASIM
Get PDFThe 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
The ASIM Mission on the International Space Station
Get PDFThe Atmosphere-Space Interactions Monitor (ASIM) is an instrument suite on the International Space Station (ISS) for measurements of lightning, Transient Luminous Events (TLEs) and Terrestrial Gamma-ray Flashes (TGFs). Developed in the framework of the European Space Agency (ESA), it was launched April 2, 2018 on the SpaceX CRS-14 flight to the ISS. ASIM was mounted on an external platform of ESA’s Columbus module eleven days later and is planned to take measurements during minimum 3 years. The instruments are an x- and gamma-ray monitor measuring photons from 15 keV to 20 MeV, and an array of three photometers and two cameras measuring in bands at: 180–250 nm, 337 nm and 777.4 nm. Additional objectives that can be addressed with the instruments relate to space physics like aurorae and meteors, and to Earth observation such as dust- and aerosol effects on cloud electrification. The paper describes the scientific objectives of the ASIM mission, the instruments, the mission architecture and the international collaboration supported by the ASIM Science Data Centre. ASIM is the first space mission with a comprehensive suite of instruments designed to measure TLEs and TGFs. Two companion papers describe the instruments in more detail (Østgaard et al. in Space Sci. Rev., 2019; Chanrion et al. in Space Sci. Rev., 2019)
Optimisation of a Horizontal Capsule Transporting Pipeline carrying Cylindrical Capsules
Get PDFPipelines 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
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