Ändra sökning
Avgränsa sökresultatet
6789 401 - 422 av 422
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Träffar per sida
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
Markera
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 401.
    Wang, Yuming
    et al.
    Nanjing Tech University, China; Linkoping University .
    Jafari, Mohammad Javad
    Linköping University .
    Wang, Nana
    Nanjing Tech University, China.
    Qian, Deping
    Linkoping University.
    Zhang, Fengling
    Linkoping University.
    Ederth, Thomas
    Linkoping University.
    Moons, Ellen
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Wang, Jianpu
    Nanjing Technical University, China.
    Inganas, Olle
    Linköping University.
    Huang, Wei
    Nanjing Technical University, China.
    Gao, Feng
    Linkoping University.
    Light-induced degradation of fullerenes in organic solar cells: a case study on TQ1:PC71BM2018Ingår i: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 6, nr 25, s. 11884-11889Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The stability of organic solar cells (OSCs) is critical for practical applications of this emerging technology. Unfortunately, in spite of intensive investigations, the degradation mechanisms in OSCs have not been clearly understood yet. In this report, we employ a range of spectroscopic and transport measurements, coupled with drift-diffusion modelling, to investigate the light-induced degradation mechanisms of fullerene-based OSCs. We find that trap states formed in the fullerene phase under illumination play a critical role in the degradation of the open-circuit voltage (V-OC) in OSCs. Our results indicate that the degradation is intrinsic to the fullerenes in OSCs and that alternative acceptor materials are desired for the development of stable OSCs.

  • 402.
    Wassborg, Pär
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Tribological evaluation of the contact between upper compression ring and cylinder liner with different surface coatings2016Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The constant pursuit in the automotive industry to increase the engines performance, new solutions are always developed and tested to reduce the friction and increase the efficiency in the engine. One component that contributes to friction losses is the piston ring pack where the top compression stands for up to 40 %. This master thesis collaborated with Scania’s material science department Basic engine and covers the friction and wear of four different materials on the cylinder liner surface against the top compression ring.The four tested materials were grey cast iron with different honing quality and three atmospheric plasma sprayed coatings with titanium oxide, chromium oxide and Metco’s mixture F2071 which is a stainless steel mixed with a ceramic. A martensitic steel piston ring with a chromium coated sliding surface was used for all the testing in the Cameron-Plint TE77 test-rig. This is a pin-on-disc test method and the parameters used for testing is set to replicate the environment the ring is exposed to at the top dead centre.The test-rig has been in Scania’s possession for a long time and has not always given a satisfying result. An uneven contact between the ring and liner has been a problem resulting in only worn edges of the liner specimen. The piston ring holder was therefore redesigned to be able to adjust the radius of the ring. This allowed a good conformability between the ring and liner to be obtained.The tested materials were evaluated according to friction and wear. Friction was measured with the test-rig and the wear was calculated with surface profiles that were measured before and after testing. Worn surfaces were studied in a SEM to verify which wear mechanism that was active. The changes of the surfaces was studied with the use of following surface parameters Ra, Rk, Rpk, Rvk and if there was a connection between these parameters and friction and wear coefficient.Independent of honing quality showed the grey cast iron lowest friction coefficient just under 0.13, the F2071 liner showed a friction coefficient just above 0.13. Both oxide layers showed similar friction where the chromium oxide had a friction just below 0.15 and the titanium oxide lay just above 0.15. Lowest wear coefficient had the chromium oxide followed by F2071, titanium oxide and the bad honed grey cast iron. These three liners showed almost the exact same wear coefficient. Worst wear coefficient had the grey cast iron with a good honing quality. A mild abrasive wear mechanism was active during the wear test and vague wear marks was found on the surface. There is no connection between wear coefficient and friction and the change in surface roughness during the test does not affect the friction.

  • 403.
    Weinesson, Linnéa
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013), Science, Mathematics and Engineering Education Research (SMEER).
    Climate Neutral Management: Implement Circular Economy in the Construction Industry2019Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Byggbranschen släpper ut en betydande mängd växthusgaser i atmosfären, använder mycket resurser och genererar mycket avfall. Dessa handlingar är inte hållbara och industrin har därför skapat en färdplan över huruvida de ska bli klimatneutrala till 2045. Några saker som lyfts fram i denna färdplan är vikten av ledarskap och en omställning till cirkulär ekonomi, däremot har befintlig forskning inte berört sambandet mellan dessa i byggprojekt. Denna studie syftar till att förstå och bedöma implementeringen av cirkulär ekonomis påverkan på ledarskapet av byggprojekt. För att uppfylla detta syfte utformades ett teoretiskt ramverk bestående av potentiella tillämpningar av cirkulär ekonomi i byggprojekt. Sambandet mellan dessa tillämpningar och projektledningen undersöktes sedan i en empirisk studie som bestod av en kvalitativ fallstudie med dokumentanalyser, projektobservationer och intervjuer med olika projektledarroller inom ett svenskt byggföretag. Resultaten antyder att implementeringen påverkar ledarna till att fokusera mer på helheten och tänka genom metodvalen. Förskottsplanering är väsentligt samt att diskutera lösningar för att optimera resursanvändningen, ha god och tidig kommunikation med rätt leverantörer och andra byggarbetsplatser, och en noggrann mängdning av godkända material samt fokusera på hanteringen av dessa. Dessutom är det viktigt att göra en ordentlig inskrivning av nyanställda samt att leda dessa mot högt satta miljömål. Slutligen visade resultatet att det är svårt att precisera endast en ledare som påverkas av en specifik tillämpning, eftersom alla är involverade i implementeringen av cirkulär ekonomi.

  • 404.
    Yadroitsev, I.
    et al.
    Cent Univ Technol, Dept Mech & Mechatron Engn, ZA-9300 Bloemfontein, Free State, South Africa.
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Yadroitsava, I.
    Cent Univ Technol, Dept Mech & Mechatron Engn, ZA-9300 Bloemfontein, Free State, South Africa.
    Du Plessis, A.
    Univ Stellenbosch, CT Scanner Facil, ZA-7602 Stellenbosch, South Africa.
    Qualification of Ti6Al4V ELI Alloy Produced by Laser Powder Bed Fusion for Biomedical Applications2018Ingår i: JOM: The Member Journal of TMS, ISSN 1047-4838, E-ISSN 1543-1851, Vol. 70, nr 3, s. 372-377Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Rectangular Ti6Al4V extralow interstitials (ELI) samples were manufactured by laser powder bed fusion (LPBF) in vertical and horizontal orientations relative to the build platform and subjected to various heat treatments. Detailed analyses of porosity, microstructure, residual stress, tensile properties, fatigue, and fracture surfaces were performed based on x-ray micro-computed tomography, scanning electron microscopy, and x-ray diffraction methods. The types of fracture and the tensile fracture mechanisms of the LPBF Ti6Al4V ELI alloy were also studied. Detailed analysis of the microstructure and the corresponding mechanical properties were compared against standard specifications for conventional Ti6Al4V alloy for use in surgical implant applications. Conclusions regarding the mechanical properties and heat treatment of LPBF Ti6Al4V ELI for biomedical applications are made.

  • 405.
    Yadroitsev, Igor
    et al.
    South Africa.
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Yadroitsava, I.
    South Africa.
    A systematic approach to manufacturing parts with desired properties by selective laser melting2015Ingår i: Materials Science and Technology Conference and Exhibition 2015, MS and T 2015, Association for Iron and Steel Technology, AISTECH , 2015, Vol. 1, s. 121-128Konferensbidrag (Refereegranskat)
    Abstract [en]

    Selective laser melting (SLM) is becoming a powerful additive manufacturing technology for different industries: automotive, medical, chemical, aerospace, etc. The extension of applications requires a wide spectrum of powder materials with specific properties. To produce parts with tailored properties by SLM, optimal process-parameters and scanning strategies have to be used for different powders. Numerical simulation allows the estimation of temperature distribution during laser melting and prediction the final microstructures and properties of SLM object. A hierarchical approach, including systematic analysis of SLM parameters necessary to control the final product quality on every level - track, layer, 3D object is suggested and discussed. A series of single tracks, layers and 3D objects were manufactured from metal powders to validate a proposed algorithm. The efficiency of the approach was illustrated by the manufacturing of fully dense samples from AISI 420 stainless steel.

  • 406. Yadroitsev, Igov
    et al.
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Yadroitsava, Inna
    Titanium Alloys Manufactured by In Situ Alloying During Laser Powder Bed Fusion2017Ingår i: JOM: The Member Journal of TMS, ISSN 1047-4838, E-ISSN 1543-1851, Vol. 69, nr 12, s. 2725-2730Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This work is focused on the investigation and understanding of in situ processes in Ti-15%Mo and Ti6Al4V-1.38%Cu alloys by laser powder bed fusion (LPBF). In both materials, Mo and Cu were introduced as elemental powders into the precursor powder mixture. The effect of process parameters, i.e., energy input on surface morphology and homogeneity, was investigated. The importance of different thermophysical properties of blended powders is also discussed. The chemical composition of phases and phase distribution in sintered materials were investigated by means of scanning electron microscopy. The mechanical properties of in situ alloyed as-built LPBF specimens were determined. The results obtained developed knowledge that is important for understanding the in situ alloying process during LPBF, and they create a base for synthesizing new materials.

  • 407.
    Yadroitsev, Igov
    et al.
    Department of Mechanical and Mechatronic Engineering, Bloemfontein, Central University of Technology, Free State, South Africa.
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Yadroitsava, Inna
    Department of Mechanical and Mechatronic Engineering, Bloemfontein, Central University of Technology, Free State, South Africa.
    Du Plessis, Anton
    University of Stellenbosch.
    Qualification of DMLS Ti6Al4V (ELI) alloy for biomedical applications2017Ingår i: Proceedings of the 28th Annual International Solid Freedom Fabrication symposium – an Additive Manufacturing conference 2017 / [ed] David L. Bourell, Richard H. Crawford, Carolyn C. Seepersad, Joseph J. Beaman & Scott Fish, Austin: University of Texas , 2017Konferensbidrag (Refereegranskat)
  • 408.
    Yaghoubi, Saba Tahaei
    et al.
    Aalto University, Finland.
    Mousavi, Mahmoud
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013). Aalto University, Finland.
    Paavola, Juha
    Aalto University, Finland.
    Size effects on centrosymmetric anisotropic shear deformable beam structures2017Ingår i: Zeitschrift für angewandte Mathematik und Mechanik, ISSN 0044-2267, E-ISSN 1521-4001, Vol. 97, nr 5, s. 586-601Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, the size effect on beam structures with centrosymmetric anisotropy is studied within strain gradient elasticity theory. Applying dimension reduction to the three dimensional anisotropic gradient elasticity, the third-order shear deformable (TSD) beam is analysed. A variational approach is used to determine the equilibrium equations of TSD beam together with consistent (classical and non-classical) boundary conditions. The TSD beam theory which is suitable for deep beam structures can be replaced by (less complicated) Euler-Bernoulli beam model for thin beam structures. The anisotropic Euler-Bernoulli beam model is also formulated within the framework of strain gradient theory. This anisotropic beam theory can be used to study size effects for any types of centrosymmetric anisotropy. To address the more practical cases of composite structures, the formulation is simplified for orthotropic and transversely isotropic materials. Finally, the analytical solutions are provided for bending of simply supported (TSD and Euler-Bernoulli) beams as well as clamped Euler-Bernoulli beams. The effect of the crystal orientation with respect to the beam geometry is investigated in these examples.

  • 409.
    Yaghoubi, SabaTahaei
    et al.
    Aalto university, Finland.
    Mousavi, Mahmoud
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013). Aalto university, Finland.
    Paavola, Juha
    Aalto university, Finland.
    Buckling of centrosymmetric anisotropic beam structures within strain gradient elasticity2017Ingår i: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 109, s. 84-92Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Buckling of centrosymmetric anisotropic beams is studied within strain gradient theory. First, the three dimensional anisotropic gradient elasticity theory is outlined. Then the dimension of the three dimensional theory is reduced, resulting in Timoshenko beam as well as Euler–Bernoulli beam theories. The governing differential equations together with the consistent (classical and non-classical) boundary conditions are derived for centrosymmetric anisotropic beams through a variational approach. By considering von Kármán nonlinear strains, the geometric nonlinearity is taken into account. The obtained nonlinear formulation can be used to study the postbuckling configuration. The analysis of size effect on anisotropic beam structures is missing in the literature so far, while the present model allows one to characterize the size effect on the buckling of the centrosymmetric anisotropic micro- and nano-scale beam structures such as micropillars. As a specific case, the governing buckling equation is obtained for the more practical case of orthotropic beams. Finally, the buckling loads for orthotropic simply supported Timoshenko and Euler–Bernoulli beams as well as a clamped Euler–Bernoulli beam are obtained analytically and the effect of the internal length scale parameters on the buckling load is depicted.

  • 410.
    Yasir, Irshad
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik, Science, Mathematics and Engineering Education Research (SMEER).
    A study of a stochastic differential equation based model for wireless channels2008Självständigt arbete på avancerad nivå (magisterexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    An autoregressive (AR) first order model is often used for modelling wireless channels. This is done in spite of the fact that a satisfactory physical explanation for this model has been missing. However, in the recent paper [Feng, Field and Haykin. 2007] derive a model in form of a first order stochastic differential equation (SDE) from a stochastic description of the scattered electric field. After discretizing this SDE, a physically motivated first order AR model is obtained.

  • 411.
    Yong-an, Min
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013). Shanghai University, China.
    Bergström, Jens
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Xiao-chun, Wu
    Shanghai University, China.
    Luo-ping, Xu
    Shanghai University, China.
    Oxidation and Thermal Fatigue Behaviors of Two Type Hot Work Steels During Thermal Cycling2013Ingår i: Journal of Iron and Steel Research International, ISSN 1006-706X, E-ISSN 2210-3988, Vol. 20, nr 11, s. 90-97Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Thermal fatigue test has been carried out on widely used hot work steel 4Cr5MoSiV1 and a low alloyed steel 3Cr3MoV in temperature range of 200 to 700 degrees C. Tempering resistance, as well as high temperature hardness/strength of steel specimens, works as a dominating material parameter on thermal fatigue resistance. During the heating period, high hardness can depress the inelastic deformation. This deformation is the origination of tensile stress, which acts as the driving force of heat checking during the cooling period. The cyclic strain-oxidation interaction can speed up the damage on surface defects, which plays an obvious role in initiation of thermal cracks. On 4Cr5MoSiV1 steel specimens, borders between the matrix and inclusions such as titanium compounds, or lager carbides such as primary carbides, are focused by strain and attacked by oxidation, and are main initiating places of cracks. While on 3Cr3MoV steel specimens, larger strain causes plastic deformation concentrating around grain boundaries. Then the following oxidation accelerates this grain boundary damage and creates cracks.

  • 412.
    Zhang, Cheng
    et al.
    Waseda University, Japan.
    Ohashi, Takumi
    Tokyo Institute of Technology, Japan.
    Saijo, Miki
    Tokyo Institute of Technology, Japan.
    Solis, Jorge
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Takeda, Yukio
    Tokyo Institute of Technology, Japan.
    Lindborg, Ann-Louise
    Camanio Care AB, Sweden.
    Takeda, Ryuta
    Leave a Nest Co. Ltd., Japan.
    Tanaka, Yoshiaki
    Waseda University, Japan.
    A Monte Carlo based computation offloading algorithm for feeding robot IoT system2018Ingår i: Smart Computing and Communication / [ed] M. Qiu, Springer, 2018, s. 163-171Konferensbidrag (Refereegranskat)
    Abstract [en]

    Ageing is becoming an increasingly major problem in European and Japanese societies. We have so far mainly focused on how to improve the eating experience for both frail elderly and caregivers by introducing and developing the eating aid robot, Bestic, made to get the food from plate to the mouth for frail elderly or person with disabilities. We expand the functionalities of Bestic to create food intake reports automatically so as to decrease the undernutrition among frail elderly and workload of caregivers through collecting data via a vision system connected to the Internet of Things (IoT) system. Since the computation capability of Bestic is very limited, computation offloading, in which resource intensive computational tasks are transferred from Bestic to an external cloud server, is proposed to solve Bestic’s resource limitation. In this paper, we proposed a Monte Carlo algorithm based heuristic computation offloading algorithm, to minimize the total overhead of all the Bestic users after we show that the target optimization problem is NP-hard in a theorem. Numeric results showed that the proposed algorithm is effective in terms of system-wide overhead.

  • 413.
    Zhang, Hanmin
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Hirvonen Grytzelius, Joakim
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Johansson, Lars
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Thin Mn germanide films studied with XPS, STM, and XMCD2013Ingår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 88, nr 4, s. 045311-1-045311-6Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Thin Mn germanide films with nanoscale thicknesses on Ge(111) have been studied by low-energy electron diffraction (LEED), scanning tunneling microscopy (STM), core-level spectroscopy (CLS), and x-ray magnetic circular dichroism. The 260 C annealing of 16 monolayers of Mn deposited on Ge(111)c(2×8) resulted in a uniform film with intense threefold split √3×√3 LEED spots and Moiré patterns in the STM images. This ultrathin film shows a clear ferromagnetism with a Curie temperature of ∼250 K. High-resolution Ge 3d CLS spectra were recorded with photon energies between 50 and 90 eV at normal and 60 emission angle. To achieve a consistent fit over the energy and angular range three components were used in the line-shape analysis. The low temperature (260 C) annealed film shows significant differences in terms of electronic structure and magnetism in contrast to the high temperature (330 C or above) annealed ones. Our results indicate that the annealing temperature and the Mn coverage play important roles in the formation of a thin magnetic Mn germanide film.

  • 414.
    Zhang, Hanmin
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013). CMM, Characterization and modeling of materials.
    Holleboom, Thijs Jan
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Johansson, Lars
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Band splitting of quantum wells of thin Ag films on Sn/Si(111)√3×√32017Ingår i: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 96, nr 4, s. 041402-1-041402-6Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    High-resolution valence band spectra of ultrathin Ag films on Sn/Si(111)√3×√3 show intrinsic splitting of the quantum-well states (QWSs). Especially at low coverages, the QWSs of such a system display delicate coupling characters with the bulk bands from the substrate. The observed QWS splitting agrees well with the result of the theoretical calculation. We found that the splitting originates from an interface with a finite thickness. In addition, the interface also causes a large sp band splitting due to the Umklapp scattering in the Γ−M direction of the Ag(111) surface Brillouin zone.

  • 415.
    Zhang, Hanmin
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Johansson, Lars
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Electronic structure of PTCDA on Sn/Si(111)-2√3×2√32014Ingår i: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 439, s. 71-78Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The electronic structures of PTCDA on the Sn/Si(111)-2√3×2√3 surface have been thoroughly studied by high-resolution photoelectron spectroscopy and near-edge X-ray absorption fine structure (NEXAFS). Upon deposition of PTCDA, there is an unusual charge transfer from the Sn/Si(111)-2√3×2√3 surface to the molecules. This is clearly shown by a new component in the Sn 4d core-level spectra that shifts towards higher binding energy. In contrast to the literature, the charge provided by Sn is donated to the carbonyl C instead of the O atoms. This is revealed by a new component in the C 1s core-level spectra that shifts towards lower binding energy. The charge transfer causes a splitting of the HOMO level in the valence band spectra. As indicated in the NEXAFS spectra, it also induces a splitting of the LUMO level of the molecules. For thick films the NEXAFS results suggest a layer by layer growth mode.

  • 416.
    Zhang, Xiaojing
    et al.
    ABB Corporate Research.
    Lindberg, Therese
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Svensson, Krister
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Vyatkin, Valeriy
    Department of Computer Science, Electrical and Space Engineering at LuleåUniversity of Technology, Sweden and the Department of Electrical Engineering and Automation, Aalto University, Finland.
    Mousavi, Arash
    Department of Computer Science, Electrical and Space Engineering at LuleåUniversity of Technology, Sweden.
    Power Consumption Modeling of Data Center IT Room with Distributed Air Flow2016Ingår i: International Journal of Modeling and Optimization, ISSN 2010-3697, Vol. 6, nr 1, s. 33-38Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Modern data centers are characterized by large sizes, high energy consumption and complexity involving IT, power supply, ventilation and cooling. Data center energy efficiency is a major concern for data center design and operation. To improve data center energy efficiency through efficient cooling and ventilation, advanced process control and optimization, process models to describe the process power consumption are required. In this work, data center power consumption models are investigated. A concept of distributed air flow control is presented. The objective is to develop a comprehensive data center power consumption model to describe IT room, computer room air handling (CRAH), data center ventilation and cooling characteristics as well as distributed air flow control. Data center operation scenarios with uneven IT load are simulated. Results show that the distributed air flow control can save the cooling energy significantly.

  • 417. Zhang, Xiaojing
    et al.
    Lindberg, Therese
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Xiong, N.
    Vyatkin, Valeriy
    Mousavi, Atash
    Cooling Energy Consumption Investigation of Data Center IT Room with Vertical Placed Server2017Ingår i: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 105, s. 2047-2052Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    As energy consumption by cooling data center IT equipment can be over 40 % of total energy consumption, efficient cooling for large data centers is essential for reducing operation costs. Modern data centers are complex systems involving IT facilities, power system, cooling and ventilation systems. In our previous work, literature study was made to investigate available data center energy consumption models; and energy consumption models for data center IT room with distributed air flow control were developed. In this paper, the models are further extended and developed to cover the combined distributed air flow control and vertical placed servers in raised floor ventilation system. Simulation of the three types of ventilation systems with Even load, Idle server and Uneven load scenarios showed that significant cooling energy consumed by a traditional ventilation system can be saved by applying the proposed new concept and method. (C) 2017 The Authors. Published by Elsevier Ltd.

  • 418.
    Züfle, Simon
    et al.
    Fluxim AG, Switzerland; Institute of Computational Physics, ZHAW, Switzerland.
    Hansson, Rickard
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Katz, Eugene A.
    The Ben-Gurion University of the Negev, Israel.
    Moons, Ellen
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Initial photo-degradation of PCDTBT:PC 70 BM solar cells studied under various illumination conditions: Role of the hole transport layer2019Ingår i: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 183, nr 1, s. 234-239Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    ncapsulated organic solar cells often show a burn-in behaviour under illumination. This burn-in manifests itself as a rapid performance loss followed by a much slower progression of the degradation. Here we investigate the burn-in for PCDTBT:PC 70 BM solar cells under a wide range of illumination intensities. We find that increasing the sunlight concentration from 1 Sun to up to 100 Suns does not change the degradation behaviour, i.e. the dependence of all principal photovoltaic parameters on the dose of solar exposure (in Sun hours). This suggests that the degradation mechanisms under solar concentration (≤100 Suns) are the same as those observed under 1 Sun. This result makes it possible to use concentrated sunlight for accelerated stability assessment of these devices. We also find that devices with PEDOT:PSS as hole transport material show a rapid drop in open-circuit voltage of around 100 mV during the first Sun hour of light exposure. By replacing PEDOT:PSS with MoO 3 this initial process can be prevented and only the much slower part of the photo-degradation takes place.

  • 419.
    Åsberg, Mikael
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Fredriksson, Gunnel
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Hatami, Sepehr
    Sverea IVF, Gotenburg.
    Fredriksson, Wendy
    Bodycote Hot Isostatic Pressing AB.
    Influence of HIP on microstructure, pore elimination and tensile properties of SLM manufactured H13 tool steel2017Konferensbidrag (Övrigt vetenskapligt)
  • 420.
    Åsberg, Mikael
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Fredriksson, Gunnel
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Hatami, Sepehr
    Swerea IVF AB.
    Fredriksson, Wendy
    Bodycote Hot Isostatic Pressing.
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Influence of post treatment on microstructure, porosity and mechanical properties of additive manufactured H13 tool steel2019Ingår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 742, s. 584-589Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Additive manufacturing (AM) is an attractive manufacturing technology in tooling applications. It provides unique opportunities to manufacture tools with complex shapes, containing inner channels for conformal cooling. In this investigation, H13, a widely used tool steel, was manufactured using a laser powder bed fusion method. Microstructure, tensile mechanical properties, hardness, and porosity of the AM H13 after stress relieve (SR), standard hardening and tempering (SR + HT), and hot isostatic pressing (SR + HIP + HT) were investigated. It was found that the microstructure of directly solidified colonies of prior austenite, which is typical for AM, disappeared after austenitizing at the hardening heat treatment. In specimens SR + HT and SR + HIP + HT, a microstructure similar to the conventional but finer was observed. Electron microscopy showed that SR and SR + HT specimens contained lack of fusion, and spherical gas porosity, which resulted in remarkable scatter in the observed elongation to break values. Application of HIP resulted in the highest strength values, higher than those observed for conventional H13 heat treated in the same way. The conclusion is that HIP promotes reduction of porosity and lack of fusion defects and can be efficiently used to improve the mechanical properties of AM H13 tool steel.

  • 421.
    Åström, Maria
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Vad kännetecknar ämnestexter? (inriktning fysik)2016Övrigt (Övrigt vetenskapligt)
  • 422.
    Östersjö, Victor
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Supersymmetry for the Hydrogen Atom2015Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    In this thesis it will be shown that the hydrogen atom has a SU(2) × SU(2) symmetry generated by the quantum mechanical angular momentum and Runge-Lenz vector operators. Additionally, the hydrogenic atom will be studied with supersymmetric methods to identify a supersymmetry that relates different such systems. This thesis is intended to present the material in a manner accessible to people without background in Lie groups and supersymmetry, as well as fill in some calculations between steps that are not spelt out in the litterature.

6789 401 - 422 av 422
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf