| 1. |
- Hallberg, Håkan, et al.
(författare)
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Modeling of Continuous Dynamic Recrystallization in Aluminum
- 2009
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Ingår i: DCE Technical Memorandum No. 11. - 1901-7278. ; 11, s. 59-62
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Konferensbidrag (refereegranskat)abstract
- A constitutive model is presented, considering grain size refinement through continuous dynamic recrystallization together with an evolving dislocation density. The grain refinement is allowed to influence both the evolution of the dislocation density and the rate dependence of the material. The model is calibrated against experimental data on aluminum and numerical simulations of equal channel angular pressing (ECAP) material processing illustrates the capabilities of the model.
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| 2. |
- Maximov, Ivan, et al.
(författare)
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Nanoimprint lithography for fabrication of three-terminal ballistic junctions in InP/GaInAs
- 2002
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484. ; 13:5, s. 666-668
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Tidskriftsartikel (refereegranskat)abstract
- We present processing technology and characterization results for InP/GaInAs two-dimensional electron gas (2DEG) three-terminal ballistic junction (TBJ) devices manufactured using nanoimprint lithography (NIL). To transfer sub-100 nm features into a high-mobility InP-based 2DEG material, we used SiO2/Si stamps made using electron beam lithography and reactive ion etching. After NIL, the resist residues are removed in oxygen plasma; this is followed by wet etching of InP/GaInAs to define the TBJ structures. Fabricated TBJ devices are characterized using scanning electron microscopy and electron transport measurements. Highly non-linear electrical characteristics as predicted by the theory (Xu H Q 2001 APPI. Phys. Lett. 78 2064) are demonstrated.
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| 3. |
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| 4. |
- Bollen, Math, et al.
(författare)
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On operational risk assessment in transmission systems : weather impact and illustrative example
- 2008
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Ingår i: Proceedings of the 10th International Conference on Probabilistic Methods Applied to Power Systems. - Piscataway, NJ : IEEE Communications Society. - 9781934325216 ; , s. 218-223
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Konferensbidrag (refereegranskat)abstract
- This paper discusses a number of aspects of operational-risk assessment of transmission systems. perational-risk assessment uses techniques developed from reliability analysis to predict the performance of the transmission system during a short period of time (several hours) starting from a well-defined operational state. The influence of weather parameters on the momentary failure rate and the operational risk is discussed in this paper as well. The operational-risk method is illustrated by means of a simple but realistic transmission-system model. The paper also discusses some of the applications for such methods in operation and planning of transmission systems.
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| 5. |
- Donzel-Gargand, Olivier, et al.
(författare)
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Cu-depleted patches induced by presence of K during growth of CIGS absorbers
- 2017
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Konferensbidrag (refereegranskat)abstract
- The conversion efficiency of the CIGS thin film solar cells has rapidly increased since introduction of the heavier alkali-doping (K, Rb, Cs). While the exclusive introduction of Na in the CIGS films has led to efficiencies up to 20,4% 1, the latest K, Rb or Cs post deposition treatments (PDT) have increased the efficiency to 22,6% 2. The exact role of this heavy-alkali PDT is still under discussion but three explanations have been discussed in the literature. First, that the heavy alkali PDT facilitates CdCu substitution, that results in an enhanced absorber type inversion, moving the p-n junction further into the CIGS bulk 3. Second, that the main effect from heavy alkali PDT is due to the formation of a K-In-Se2 layer, that passivates defects at the CIGS surface, reducing interface recombination 4. And third, that the heavy alkali PDT induces a Cu depletion at the surface of the CIGS which, by increasing the local Fermi level, increases the band bending; thus creating a higher potential barrier for holes to recombine 5.
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| 6. |
- Donzel-Gargand, Olivier, et al.
(författare)
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Deep surface Cu depletion induced by K in high-efficiency Cu(In,Ga)Se2 solar cell absorbers
- 2018
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Ingår i: Progress in Photovoltaics. - : Wiley. - 1062-7995 .- 1099-159X. ; 26:9, s. 730-739
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we used K‐rich glass substrates to provide potassium during the coevaporation of Cu(In,Ga)Se2 (CIGS) absorber layers. Subsequently, we applied a postdeposition treatment (PDT) using KF or RbF to some of the grown absorbers. It was found that the presence of K during the growth of the CIGS layer led to cell effi- ciencies beyond 17%, and the addition of a PDT pushed it beyond 18%. The major finding of this work is the observation of discontinuous 100‐ to 200‐nm‐deep Cu‐ depleted patches in the vicinity of the CdS buffer layer, correlated with the presence of K during the growth of the absorber layer. The PDT had no influence on the forma- tion of these patches. A second finding concerns the composition of the Cu‐depleted areas, where an anticorrelation between Cu and both In and K was measured using scanning transmission electron microscopy. Furthermore, a steeper Ga/(In+Ga) ratio gradient was measured for the absorbers grown with the presence of K, suggesting that K hinders the group III element interdiffusion. Finally, no Cd in‐diffusion to the CIGS layer could be detected. This indicates that if CdCu substitution occurs, either their concentration is below our instrumental detection limit or its presence is contained within the first 6 nm from the CdS/CIGS interface.
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| 7. |
- Beretta, Michela, et al.
(författare)
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Why and How Firms Implement Internal Crowdsourcing Platforms
- 2023
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Ingår i: IEEE Transactions on Engineering Management. - 0018-9391 .- 1558-0040. ; 70:9, s. 3036-3049
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Tidskriftsartikel (refereegranskat)abstract
- Internal crowdsourcing platforms enable firms to involve a wider crowd of employees beyond the R&D department in the generation and development of ideas for innovation. Prior studies emphasize firm-level functional benefits, e.g., accessing larger and more diverse sets of ideas, competences, and expertise as well as reducing the costs for innovation. Inspired by the behavioral theory of the firm, we depart from such functionalist approach and develop a model that explains why and how managers in large organizations implement and design internal crowdsourcing. Drawing on a qualitative, multiple case study of five large organizations, we identify three key motives that underpin managers’ decision to implement an internal crowdsourcing platform: problem-stimulated, opportunity-driven, and legitimacy-seeking. Next, we discuss how such different motives drive managers’ decisions regarding their design of the internal crowdsourcing initiative. Broadly, our results help explain why firms continue to invest in crowdsourcing initiatives despite meager results and how managers’ cognitive frameworks impact heterogeneity in the design and implementation of crowdsourcing initiatives. This article contributes to the crowdsourcing literature by providing a more multifaceted picture of internal crowdsourcing than previous research has suggested. From a practitioners’ perspective, awareness and recognition by managers of the potential pitfalls in implementing and designing these platforms stand out as an important first step toward improving the effectiveness of internal crowdsourcing.
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| 8. |
- Bergström, Annika, et al.
(författare)
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Conclusion
- 2017
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Ingår i: Books on screens. - Gothenburg : Nordicom. ; , s. 209-218
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 9. |
- Edoff, Marika, 1965-, et al.
(författare)
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High Voc in (Cu,Ag)(In,Ga)Se2 Solar Cells
- 2017
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Ingår i: IEEE Journal of Photovoltaics. - 2156-3381 .- 2156-3403. ; 7:6, s. 1789-1794
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Tidskriftsartikel (refereegranskat)abstract
- In this contribution, we show that silver substitution for copper in Cu(In,Ga)Se-2 (CIGS) to form (Ag,Cu)(In, Ga)Se-2 (ACIGS) leads to a reduction of the voltage loss expressed as E-g/q-V-oc. This, in turn, leads to higher device efficiencies as compared to similar CIGS devices without Ag. We report V-oc at 814 mV at a conversion efficiency of 21% for our best ACIGS device with 20% of the group I element consisting of silver. Comparing ACIGS and CIGS devices with the same Ga/(Ga+ In) ratio, the ACIGS devices exhibit about 0.05 eV higher bandgap. Alkali postdeposition treatment with KF leads to improvements in efficiency both for CIGS and ACIGS, but we find that the dose of KF needed for optimum device for ACIGS is 10-20% of the dose used for CIGS.
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| 10. |
- Hatami, Sepehr, 1981, et al.
(författare)
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Critical aspects of sinter-hardening of prealloyed Cr-Mo steel
- 2010
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Ingår i: Journal of Materials Processing Technology. - : Elsevier BV. - 0924-0136. ; 210:9, s. 1180-1189
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Tidskriftsartikel (refereegranskat)abstract
- In recent years, growing demand for greater mechanical properties of PM steel components with competitive fabrication cost has led to significant innovations in different fields of powder metallurgy. Recent research has been focused on reaching higher performance with lower cost. To this end, the possibility of combining the conventional sintering and post-sintering processes for a particular powder composition has been introduced. Sinter-hardening is a result of the research conducted along this line. Elimination of any secondary operation such as quench-hardening by incorporating it in the sintering process (i.e. sinter-hardening) is of great interest, as it will lead to lower processing costs and equal, if not higher mechanical performance. However, to ensure the desired mechanical properties of the final component and robustness of the performance, critical aspects of the sinter-hardening process should be rigorously studied. Hence with specific attention to a Cr-Mo steel powder (FL-5305), this study deals with the influence of density on cooling rate, the effect of different sintering temperatures (e.g. 1120 degrees C and 1250 degrees C) on austenite grain size and consequently, hardenability. The microstructure development in sinter-hardened FL-5305 material has been analyzed and predicted by means of the available literature for solid steel and also using the commercial software (JMatPro 5.0) for materials assessment based on thermodynamic and kinetics modeling. Finally, inaccurate carbon control and its adverse impact on excessive formation of cementite have been addressed. (C) 2010 Elsevier B.V. All rights reserved.
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