SwePub
Sök i SwePub databas

  Utökad sökning

Träfflista för sökning "WFRF:(Johansson V.) srt2:(2015-2019);srt2:(2016);hsvcat:2"

Sökning: WFRF:(Johansson V.) > (2015-2019) > (2016) > Teknik

  • Resultat 1-10 av 14
Sortera/gruppera träfflistan
   
NumreringReferensOmslagsbildHitta
1.
  • Bokhorst, Stef, et al. (författare)
  • Changing Arctic snow cover : A review of recent developments and assessment of future needs for observations, modelling, and impacts
  • 2016
  • Ingår i: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 45:5, s. 516-537
  • Forskningsöversikt (refereegranskat)abstract
    • Snow is a critically important and rapidly changing feature of the Arctic. However, snow-cover and snowpack conditions change through time pose challenges for measuring and prediction of snow. Plausible scenarios of how Arctic snow cover will respond to changing Arctic climate are important for impact assessments and adaptation strategies. Although much progress has been made in understanding and predicting snow-cover changes and their multiple consequences, many uncertainties remain. In this paper, we review advances in snow monitoring and modelling, and the impact of snow changes on ecosystems and society in Arctic regions. Interdisciplinary activities are required to resolve the current limitations on measuring and modelling snow characteristics through the cold season and at different spatial scales to assure human well-being, economic stability, and improve the ability to predict manage and adapt to natural hazards in the Arctic region.
  •  
2.
  • Wu, Qiong, et al. (författare)
  • Highly Absorbing Antimicrobial Biofoams Based on Wheat Gluten and Its Biohybrids
  • 2016
  • Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 4:4, s. 2395-2404
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper presents the absorption, mechanical, and antimicrobial properties of novel types of biofoams based on wheat-gluten (WG) and its biohybrids with silica. The hybrid WG foams were in situ polymerized with silica using two different silanes. When immersed in water, the 90-95% porous WG and silica-modified hybrid WG foams showed a maximum water uptake between 32 and 11 times the original sample weight. The maximum uptake was only between 4.3 and 6.7 times the initial weight in limonene (a nonpolar liquid) but showed reversible absorption/desorption and that the foams could be dried into their original shape. The different foams had a cell size of 2-400 mu m, a density of 60-163 kg/m(3), and a compression modulus of 1-9 MPa. The integrity of the foams during swelling in water was improved by cross-linking with glutaraldehyde (GA) or by a thermal treatment at 130 degrees C, which polymerized the proteins. In the never-dried state, the foam acted as a sponge, and it was possible to squeeze out water and soak it repeatedly. If the foam was dried to its glassy state, then the cells collapsed and did not open again even if the solid foam was reimmersed in water, saving as a sensor mechanism that can be used to reveal unintended exposure to polar liquids such as water under a product's service life. Small-angle X-ray scattering revealed that the gliadin-correlated structure expanded and then disappeared in the presence of water. The foam was made antimicrobial by impregnation with a Lanasol solution (a bromophenol existing in algae). It was also shown that the foam can act as a transfer/storage medium for liquids such as natural oils (rapeseed oil) and as a slow-release matrix for surfactant chemicals.
  •  
3.
  •  
4.
  • Rasam, Amin, et al. (författare)
  • Assessment of subgrid-scale stress statistics in non-premixed turbulent wall-jet flames
  • 2016
  • Ingår i: Journal of turbulence. - : Taylor & Francis. - 1468-5248 .- 1468-5248. ; 17:5, s. 471-490
  • Tidskriftsartikel (refereegranskat)abstract
    • We investigate the heat-release effects on the characteristics of the subgrid-scale (SGS) stress tensor and SGS dissipation of kinetic energy and enstrophy. Direct numerical simulation data of a non-premixed reacting turbulent wall-jet flow with and without substantial heat release is employed for the analysis. This study comprises, among others, an analysis of the eigenvalues of the resolved strain rate and SGS stress tensors, to identify the heat-release effects on their topology. An assessment of the alignment between the eigenvectors corresponding to the largest eigenvalues of these two tensors is also given to provide further information for modelling of the SGS stress tensor. To find out the heat-release effects on the dynamics of the turbulent kinetic energy and enstrophy dissipation, probability density functions (PDFs) and mean values are analysed. The mean SGS shear stress and turbulent kinetic energy both slightly increase in the buffer layer and substantially decrease further away from the wall, due to the heat-release effects. Contrary to the kinetic energy, heat release decreases the mean SGS dissipation of enstrophy in the near-wall region. Moreover, differences in the shapes of the PDFs between the isothermal and exothermic cases indicate changes in the intermittency level of both SGS dissipations. Heat release also increases the SGS stress anisotropy in the near-wall region. Although, the structure of the mean resolved strain-rate tensor only marginally differs between the isothermal and exothermic cases in the near-wall region, substantial differences are observed in the jet area, where compressibility effects are important and heat-release effects are found to promote compression states. The differences in the relative alignment between the SGS stress and resolved strain-rate tensors in the isothermal and exothermic cases are discussed in connection with the differences in the SGS dissipation of kinetic energy.
  •  
5.
  • Yang, Tao, et al. (författare)
  • Periodic Behaviors for Discrete-Time Second-Order Multiagent Systems With Input Saturation Constraints
  • 2016
  • Ingår i: IEEE Transactions on Circuits and Systems - II - Express Briefs. - 1549-7747 .- 1558-3791. ; 63:7, s. 663-667
  • Tidskriftsartikel (refereegranskat)abstract
    • This brief considers the existence of periodic behaviors for discrete-time second-order multiagent systems with input saturation constraints. We first consider the case where the agent dynamics is a double integrator and then establish conditions on the feedback gains of the linear consensus control law for achieving periodic behaviors. This, in turn, shows that the previously established sufficient condition for reaching global consensus has a necessary aspect since these two conditions are exclusive. We further consider all other second-order agent dynamics and show that these multiagent systems under the linear consensus law exhibit periodic solutions provided the feedback gains satisfy certain conditions. Simulation results are used to validate the theoretical findings.
  •  
6.
  • Adaldo, Antonio, et al. (författare)
  • Multi-Agent Trajectory Tracking with Self-Triggered Cloud Access
  • 2016
  • Ingår i: 2016 IEEE 55th Conference on Decision and Control, CDC 2016. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781509018376 ; , s. 2207-2214
  • Konferensbidrag (refereegranskat)abstract
    • This paper presents a cloud-supported control algorithm for coordinated trajectory tracking of networked autonomous agents. The motivating application is the coordinated control of Autonomous Underwater Vehicles. The control objective is to have the vehicles track a reference trajectory while keeping an assigned formation. Rather than relying on inter-agent communication, which is interdicted underwater, coordination is achieved by letting the agents intermittently access a shared information repository hosted on a cloud. An event-based law is proposed to schedule the accesses of each agent to the cloud. We show that, with the proposed scheduling of the cloud accesses, the agents achieve the required coordination objective. Numerical simulations corroborate the theoretical results.
  •  
7.
  • Demirel, Burak, et al. (författare)
  • On the Trade-Off between Communication and Control Cost in Event-Triggered Dead-Beat Control
  • 2016
  • Ingår i: IEEE Transactions on Automatic Control. - : IEEE. - 0018-9286 .- 1558-2523. ; PP:99
  • Tidskriftsartikel (refereegranskat)abstract
    • We consider a stochastic system where the communication between the controller and the actuator is triggered by a thresholdbased rule. The communication is performed across an unreliable link that stochastically erases transmitted packets. To decrease the communication burden, and as a partial protection against dropped packets, the controller sends a sequence of control commands to the actuator in each packet. These commands are stored in a buffer and applied sequentially until the next control packet arrives. In this context, we study dead-beat control laws and compute the expected linear-quadratic loss of the closed-loop system for any given event-threshold. Furthermore, we provide analytical expressions that quantify the trade-off between the communication cost and the control performance of event-triggered control systems. Numerical examples demonstrate the effectiveness of the proposed technique.
  •  
8.
  • Grigoriev, Igor, 1984-, et al. (författare)
  • Algebraic Reynolds stress modeling of turbulence subject to rapid homogeneous and non-homogeneous compression or expansion
  • 2016
  • Ingår i: Physics of fluids. - : American Institute of Physics (AIP). - 1070-6631 .- 1089-7666. ; 28:2, s. 026101-
  • Tidskriftsartikel (refereegranskat)abstract
    • A recently developed explicit algebraic Reynolds stress model (EARSM) by Grigoriev et al. ["A realizable explicit algebraic Reynolds stress model for compressible turbulent flow with significant mean dilatation," Phys. Fluids 25(10), 105112 (2013)] and the related differential Reynolds stress model (DRSM) are used to investigate the influence of homogeneous shear and compression on the evolution of turbulence in the limit of rapid distortion theory (RDT). The DRSM predictions of the turbulence kinetic energy evolution are in reasonable agreement with RDT while the evolution of diagonal components of anisotropy correctly captures the essential features, which is not the case for standard compressible extensions of DRSMs. The EARSM is shown to give a realizable anisotropy tensor and a correct trend of the growth of turbulence kinetic energy K, which saturates at a power law growth versus compression ratio, as well as retaining a normalized strain in the RDT regime. In contrast, an eddy-viscosity model results in a rapid exponential growth of K and excludes both realizability and high magnitude of the strain rate. We illustrate the importance of using a proper algebraic treatment of EARSM in systems with high values of dilatation and vorticity but low shear. A homogeneously compressed and rotating gas cloud with cylindrical symmetry, related to astrophysical flows and swirling supercritical flows, was investigated too. We also outline the extension of DRSM and EARSM to include the effect of non-homogeneous density coupled with "local mean acceleration" which can be important for, e.g., stratified flows or flows with heat release. A fixed-point analysis of direct numerical simulation data of combustion in a wall-jet flow demonstrates that our model gives quantitatively correct predictions of both streamwise and cross-stream components of turbulent density flux as well as their influence on the anisotropies. In summary, we believe that our approach, based on a proper formulation of the rapid pressure-strain correlation and accounting for the coupling with turbulent density flux, can be an important element in CFD tools for compressible flows.
  •  
9.
  • Grigoriev, Igor, 1984-, et al. (författare)
  • Unified explicit algebraic Reynolds stress model for compressible, heat-releasing and supercritical flowswith large density variation
  • 2016
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • An explicit algebraic model (EARSM) for variable denstiy turbulent flow developed by Grigoriev et al. [Phys. Fluids (2015)] is revisited here. We apply it to a quasi one-dimensional nozzle flow, a wall-jet flow with combustion and large density variation and a supercritical flow of carbon dioxide with heat transfer and buoyancy. It is confirmed that the coupling between strong mean density gradient due to high speed, heat release or thermodynamic variations and the 'local mean acceleration' of the flow produces strong turbulent density and heat fluxes, which strongly affect the turbulence. The possible calibration branches are identified and analyzed. We show that a simple and unified calibration of the model gives good predictions for all cases considered. Therefore, the model is a reliable tool for the computation of compressible flows with large density variation.
  •  
10.
  • Lazeroms, Werner M. J., et al. (författare)
  • Study of Transitions in the Atmospheric Boundary Layer Using Explicit Algebraic Turbulence Models
  • 2016
  • Ingår i: Boundary-layer Meteorology. - : Springer. - 0006-8314 .- 1573-1472. ; 161:1, s. 19-47
  • Tidskriftsartikel (refereegranskat)abstract
    • We test a recently developed engineering turbulence model, a so-called explicit algebraic Reynolds-stress (EARS) model, in the context of the atmospheric boundary layer. First of all, we consider a stable boundary layer used as the well-known first test case from the Global Energy and Water Cycle Experiment Atmospheric Boundary Layer Study (GABLS1). The model is shown to agree well with data from large-eddy simulations (LES), and this agreement is significantly better than for a standard operational scheme with a prognostic equation for turbulent kinetic energy. Furthermore, we apply the model to a case with a (idealized) diurnal cycle and make a qualitative comparison with a simpler first-order model. Some interesting features of the model are highlighted, pertaining to its stronger foundation on physical principles. In particular, the use of more prognostic equations in the model is shown to give a more realistic dynamical behaviour. This qualitative study is the first step towards a more detailed comparison, for which additional LES data are needed.
  •  
Skapa referenser, mejla, bekava och länka
  • Resultat 1-10 av 14
Typ av publikation
tidskriftsartikel (9)
konferensbidrag (3)
rapport (1)
forskningsöversikt (1)
Typ av innehåll
refereegranskat (13)
övrigt vetenskapligt/konstnärligt (1)
Författare/redaktör
Johansson, Arne V. (6)
Dimarogonas, Dimos V ... (5)
Johansson, Karl H. (4)
Brethouwer, Geert (3)
Wallin, Stefan (3)
Liuzza, Davide (2)
visa fler...
Meng, Z. (1)
Chen, T. (1)
Gupta, V. (1)
Meng, X. (1)
Johansson, Cecilia (1)
Vervisch, Luc (1)
Schlatter, Philipp (1)
Adaldo, Antonio (1)
di Bernardo, Mario (1)
Johansson, Eva (1)
Fuchs, Laszlo (1)
Johansson, Margareta (1)
Quevedo, D. E. (1)
Brethouwer, Gert (1)
Yu, Shun (1)
Gedde, Ulf W. (1)
Hedenqvist, Mikael S ... (1)
Roth, Stephan V. (1)
Wu, Qiong (1)
Olsson, Richard T. (1)
Johansson, Mikael (1)
Svensson, Gunilla (1)
Ehrich, Dorothee (1)
Jónsdóttir, Ingibjor ... (1)
Bokhorst, Stef (1)
Pedersen, Stine Hojl ... (1)
Brucker, Ludovic (1)
Anisimov, Oleg (1)
Bjerke, Jarle W. (1)
Brown, Ross D. (1)
Essery, Richard L. H ... (1)
Heilig, Achim (1)
Ingvander, Susanne (1)
Inga, Niila (1)
Luojus, Kari (1)
Macelloni, Giovanni (1)
Mariash, Heather (1)
McLennan, Donald (1)
Rosqvist, Gunhild Ni ... (1)
Sato, Atsushi (1)
Savela, Hannele (1)
Schneebeli, Martin (1)
Sokolov, Aleksandr (1)
Sokratov, Sergey A. (1)
visa färre...
Lärosäte
Kungliga Tekniska Högskolan (13)
Stockholms universitet (2)
Uppsala universitet (1)
Sveriges Lantbruksuniversitet (1)
Språk
Engelska (14)
Forskningsämne (UKÄ/SCB)
Naturvetenskap (3)
Samhällsvetenskap (1)
År

Kungliga biblioteket hanterar dina personuppgifter i enlighet med EU:s dataskyddsförordning (2018), GDPR. Läs mer om hur det funkar här.
Så här hanterar KB dina uppgifter vid användning av denna tjänst.

 
pil uppåt Stäng

Kopiera och spara länken för att återkomma till aktuell vy