| 1. |
- Stark, Andreas, et al.
(författare)
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Hybrid digital manufacturing: Capturing the value of digitalization
- 2023
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Ingår i: Journal of Operations Management. - : Wiley. - 1873-1317 .- 0272-6963. ; 69:6, s. 890-910
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Tidskriftsartikel (refereegranskat)abstract
- A chasm is growing between the advanced technologies available for improving manufacturing operations and those effectively used in practice. The vision of Industry 4.0 is to mobilize industry to seek out these possibilities for improvement and to close the gap between opportunity and reality. However, when compared with more established improvement opportunities such as lean manufacturing, the digitalization of manufacturing lacks in both paradigmatic examples and an understanding of how to achieve the benefits. This lack is a complication of concern: Without an appropriate operations strategy to capture the value of digitalization, manufacturing companies will be unable to focus on technological investments and operational changes. To address this concern, operations management academics must develop new theory through active engagement in the practice of digitalization in manufacturing. This research presents a paradigmatic example, based on engaged scholarship, focused on effectively combining novel object-interactive and conventional manufacturing syntax for benefiting from digitalization in internal operations and the wider supply chain. The contribution to literature is a novel operations strategy—hybrid digital manufacturing—for capturing the value of Industry 4.0 technologies.
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| 2. |
- Behar, Etienne, et al.
(författare)
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Mass-loading of the solar wind at 67P/Churyumov-Gerasimenko : Observations and modelling
- 2016
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 596
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Tidskriftsartikel (refereegranskat)abstract
- Context. The first long-term in-situ observation of the plasma environment in the vicinity of a comet, as provided by the European Rosetta spacecraft.Aims. Here we offer characterisation of the solar wind flow near 67P/Churyumov-Gerasimenko (67P) and its long term evolution during low nucleus activity. We also aim to quantify and interpret the deflection and deceleration of the flow expected from ionization of neutral cometary particles within the undisturbed solar wind.Methods. We have analysed in situ ion and magnetic field data and combined this with hybrid modeling of the interaction between the solar wind and the comet atmosphere.Results. The solar wind deflection is increasing with decreasing heliocentric distances, and exhibits very little deceleration. This is seen both in observations and in modeled solar wind protons. According to our model, energy and momentum are transferred from the solar wind to the coma in a single region, centered on the nucleus, with a size in the order of 1000 km. This interaction affects, over larger scales, the downstream modeled solar wind flow. The energy gained by the cometary ions is a small fraction of the energy available in the solar wind.Conclusions. The deflection of the solar wind is the strongest and clearest signature of the mass-loading for a small, low-activity comet, whereas there is little deceleration of the solar wind.
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| 3. |
- Behar, Etienne, et al.
(författare)
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Solar wind dynamics around a comet : A 2D semi-analytical kinetic model
- 2018
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 620
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Tidskriftsartikel (refereegranskat)abstract
- Aims.We aim at analytically modelling the solar wind proton trajectories during their interaction with a partially ionised cometaryatmosphere, not in terms of bulk properties of the flow but in terms of single particle dynamics.Methods.We first derive a generalised gyromotion, in which the electric field is reduced to its motional component. Steady-stateis assumed, and simplified models of the cometary density and of the electron fluid are used to express the force experienced byindividual solar wind protons during the interaction.Results.A three-dimensional (3D) analytical expression of the gyration of two interacting plasma beams is obtained. Applying it to acomet case, the force on protons is always perpendicular to their velocity and has an amplitude proportional to 1/r2. The solar winddeflection is obtained at any point in space. The resulting picture presents a caustic of intersecting trajectories, and a circular regionis found that is completely free of particles. The particles do not lose any kinetic energy and this absence of deceleration, togetherwith the solar wind deflection pattern and the presence of a solar wind ion cavity, is in good agreement with the general results of theRosettamission.Conclusions.The qualitative match between the model and thein situdata highlights how dominant the motional electric field isthroughout most of the interaction region for the solar wind proton dynamics. The model provides a simple general kinetic descriptionof how momentum is transferred between these two collisionless plasmas. It also shows the potential of this semi-analytical modelfor a systematic quantitative comparison to the data.
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| 4. |
- Ekenbäck, Andreas, 1975-
(författare)
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Numerical modelling of ENAs from stellar wind interactions
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Energetic neutral atoms (ENAs) are produced whenever a stellar wind encounters a neutral atmosphere. If a stellar wind proton comes sufficiently close to a neutral a charge-exchange reaction may take place, transforming the proton into an ENA. Unaffected by magnetic and electric fields, ENAs provide an opportunity for global imaging of stellar wind interactions.This thesis presents methods and results of numerical modelling of stellar wind interactions. In particular it treats in depth production of ENAs at comets, Mars and the extrasolar planet HD 209458b.Sufficiently accurate numerical models of stellar wind interactions require extensive computations. Parallel computing has therefore been used throughout the work, both for fluid and particle simulations of space plasmas. This thesis describes the use of a general simulation tool, providing parallel computing for space plasma simulations.The thesis presents estimations of the magnitude and morphology of the ENA production at comets and HD 209458b. It compares the results obtained with observations and analyzes them in the light of ENA production at similar objects. Also, simulated ENA images for Mars were produced and compared to observations.
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| 5. |
- Eriksson, Jenny, 1975-, et al.
(författare)
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New ways of collecting individual travel information : Evaluation of data collection and recruitment methods
- 2018
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The overall purpose of the project is to conduct a demonstration study that shows how two data collection methods that have been developed to collect travel survey data perform in the field, and how they perform compared with traditional TS (i.e., postal questionnaires and/or telephone interviews). The project is also intended to provide a better understanding of the ways in which different recruitment methods of respondents can be used so that future TS can be more cost effective.The two collection methods tested consist of a mobile app and an online questionnaire with a map to assist the respondents to identify travel destinations. Three recruitment methods were used, i.e., recruitment via random sampling, a web panel, and crowdsourcing. The portion of the random sample that received an online questionnaire was divided into two groups. Half the group was given no incentive, while the other half received a gift card worth SEK 100 after answering the questioner. Those who were recruited via a web panel and were to use the mobile app were rewarded in the form of a gift card worth SEK 100 if, at minimum, they made corrections to trips made on one day registered in the mobile app. A nonresponse analysis was performed of the random sample for both the online questionnaire and the mobile app. Cost estimates for each collection method and recruitment method were also performed, as were uncertainty estimates.Overall, the study shows that the mobile app registered significantly more trips per respondent than did the online questionnaire, while the distances travelled were comparable. There are several possible interpretations of this. One is that people who responded to the online questionnaire either forget about and/or combined short trips (particularly trips made for the purposes of leisure or shopping, and using the travel modes walking and car). One presumable explanation for this is that it is easier to confirm/correct the trips that the mobile app suggests than it is to recall and enter all trips in an online questionnaire. Another possible interpretation is that people responding to different data collection methods have different travel patterns. Yet another explanation is connected to technique issues regarding the different data collection methods.
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| 6. |
- Eriksson, Jenny, 1975-, et al.
(författare)
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Nya sätt att samla in individuell resvaneinformation : Utvärdering av insamlings- och rekryteringsmetoder
- 2018
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Inom samverkansprogrammet Nästa generations resor och transporter, som Trafikanalys är huvudansvarig för, har man identifierat ett behov av att finna och utveckla nya lösningar för resvaneundersökningar (RVU:er). Bakgrunden till detta är bland annat sjunkande svarsfrekvenser med dagens metoder, vilket skulle kunna ge problem med representativiteten. Det anses som mycket angeläget att utveckla nya metoder för datainsamling för framtidens RVU:er, både på kort och lång sikt.Det övergripande syftet med projektet är att göra en demonstrationsstudie som visar hur två datainsamlingsmetoder som har utvecklats för att samla in resevaneundersökningsdata presterar i fält, samt hur de presterar jämfört med ”traditionell” RVU (postal enkät och/eller telefonintervjuer). Projektet syftar också till att få bättre förståelse för hur olika rekryteringsmetoder kan användas för att framtida RVU:er ska kunna bli mer kostnadseffektiva. De två insamlingsmetoder som testats är webbenkät med karta och mobilapp. Tre rekryteringsmetoder har använts och dessa är rekrytering via slumpmässigt urval, webbpanel och crowdsourcing.
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| 7. |
- Fatemi, Shahab, et al.
(författare)
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Effects of protons deflected by lunar crustal magnetic fields on the global lunar plasma environment
- 2014
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Ingår i: Journal of Geophysical Research - Space Physics. - : John Wiley & Sons. - 2169-9380 .- 2169-9402. ; 119:8, s. 6095-6105
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Tidskriftsartikel (refereegranskat)abstract
- Solar wind plasma interaction with lunar crustal magnetic fields is different than that of magnetized bodies like the Earth. Lunar crustal fields are, for typical solar wind conditions, not strong enough to form a (bow)shock upstream but rather deflect and perturb plasma and fields. Here we study the global effects of protons reflected from lunar crustal magnetic fields on the lunar plasma environment when the Moon is in the unperturbed solar wind. We employ a three-dimensional hybrid model of plasma and an observed map of reflected protons from lunar magnetic anomalies over the lunar farside. We observe that magnetic fields and plasma upstream over the lunar crustal fields compress to nearly 120% and 160% of the solar wind, respectively. We find that these disturbances convect downstream in the vicinity of the lunar wake, while their relative magnitudes decrease. In addition, solar wind protons are disturbed and heated at compression regions and their velocity distribution changes from Maxwellian to a non-Maxwellian. Finally, we show that these features persists, independent of the details of the ion reflection by the magnetic fields.
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| 8. |
- Fatemi, Shahab, et al.
(författare)
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The effects of lunar surface plasma absorption and solar wind temperature anisotropies on the solar wind proton velocity space distributions in the low-altitude lunar plasma wake
- 2012
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 117:10
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Tidskriftsartikel (refereegranskat)abstract
- We study the solar wind proton velocity space distribution functions on the lunar nightside at low altitudes (∼100 km) above the lunar surface using a three-dimensional hybrid plasma solver, when the Moon is in the unperturbed solar wind. When the solar wind encounters a passive obstacle, such as the Moon, without any strong magnetic field and no atmosphere, solar wind protons that impact the obstacle's surface are absorbed and removed from the velocity space distribution functions. We show first that a hybrid model of plasma is applicable to study the low-altitude lunar plasma wake by comparing the simulation results with observations. Then we examine the effects of a solar wind bi-Maxwellian velocity space distribution function and the lunar surface plasma absorption on the solar wind protons' velocity space distribution functions and their entry in the direction parallel to the interplanetary magnetic field lines into the low-altitude lunar wake. We present a backward Liouville method for particle-in-cell solvers that improves velocity space resolution. The results show that the lunar surface plasma absorption and anisotropic solar wind velocity space distributions result in substantial changes in the solar wind proton distribution functions in the low-altitude lunar plasma wake, modifying proton number density, velocity, and temperature there. Additionally, a large temperature anisotropy is found at close distances to the Moon on the lunar nightside as a consequence of the lunar surface plasma absorption effect
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| 9. |
- Fatemi, Shahab, et al.
(författare)
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The lunar wake current systems
- 2013
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Ingår i: Geophysical Research Letters. - : American Geophysical Union (AGU). - 0094-8276 .- 1944-8007. ; 40:1, s. 17-21
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Tidskriftsartikel (refereegranskat)abstract
- We present the lunar wake current systems when the Moon is assumed to be a non-conductive body, absorbing the solar wind plasma. We show that in the transition regions between the plasma void, the expanding rarefaction region, and the interplanetary plasma, there are three main currents flowing around these regions in the lunar wake. The generated currents induce magnetic fields within these regions and perturb the field lines there. We use a three-dimensional, self-consistent hybrid model of plasma (particle ions and fluid electrons) to show the flow of these three currents. First, we identify the different plasma regions, separated by the currents, and then we show how the currents depend on the interplanetary magnetic field direction. Finally, we discuss the current closures in the lunar wake.
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| 10. |
- Fredriksson, Anna, et al.
(författare)
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Downstream Supply Chain Effects of Direct Digital Kitting in the Construction Industry
- 2023
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Ingår i: 30th Euroma conference. ; 30
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Konferensbidrag (refereegranskat)abstract
- Solutions that improve operational efficiency in the construction industry is crucial. Direct digital kitting (DDK) is suggested for enhancing supply chain performance and reducing manhours throughout the supply chain and at construction site. We examine, by a single case, the downstream impacts of DDK enabled by a digital product innovation for components of inner walls. Potentials of DDK in construction supply chains have been assessed. The study provides insights on performance effects of DDK, requirements for its implementation, and conditions that alter the effects.
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