| 1. |
- Castleton, Christopher, 1969-, et al.
(författare)
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Managing the supercell approximation for charged defects in semiconductors : Finite-size scaling, charge correction factors, the band-gap problem, and the ab initio dielectric constant
- 2006
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 73:035215, s. 11-
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Tidskriftsartikel (refereegranskat)abstract
- The errors arising in ab initio density functional theory studies of semiconductor point defects using the supercell approximation are analyzed. It is demonstrated that (a) the leading finite size errors are inverse linear and inverse cubic in the supercell size and (b) finite size scaling over a series of supercells gives reliable isolated charged defect formation energies to around +-0.05 eV. The scaled results are used to test three correction methods. The Makov-Payne method is insufficient, but combined with the scaling parameters yields an ab initio dielectric constant of 11.6+-4.1 for InP. Gamma point corrections for defect level dispersion are completely incorrect, even for shallow levels, but realigning the total potential in real-space between defect and bulk cells actually corrects the electrostatic defect-defect interaction errors as well. Isolated defect energies to +-0.1 eV are then obtained using a 64 atom supercell, though this does not improve for larger cells. Finally, finite size scaling of known dopant levels shows how to treat the band gap problem: in < or = 200 atom supercells with no corrections, continuing to consider levels into the theoretical conductin band (extended gap) comes closest to experiment. However, for larger cells or when supercell approximation errors are removed, a scissors scheme stretching the theoretical band gap onto the experimental one is in fact correct.
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| 2. |
- Eriksson, Henrik, 1973, et al.
(författare)
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Exploring Quality Challenges and the Validity of Excellence Models
- 2016
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Ingår i: International Journal of Operations & Production Management. - 0144-3577 .- 1758-6593. ; 36:10, s. 1201-1221
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: The purpose is to identify and explore important quality-related challenges facing organizations, and how current excellence models incorporate these challenges.Methodology: The article is based on a Delphi study in Swedish organizations, 49 challenges were generated and ranked according to importance. The top 10 ranked challenges were compared to the principles of four excellence models.Findings: The excellence models seem to still be relevant since their content matches many of the challenges identified. The MBNQA and the SIQ models were found to have the most comprehensive coverage, while the ISO model had limited coverage.Research Limitations/Implications: Three areas for further research were identified: 1) how QM can evolve in different contexts with varying needs in terms of adaptive and explorative capabilities, 2) the interfaces of QM and sustainability, and ways to understand how customers and stakeholders can be active contributors to improvements and 3) the roles of the owners and board of directors in QM, and how to organize and distribute responsibilities of the QM work.Practical and Social Implications: Three important challenges could be addressed in upcoming revisions of excellence models: 1) making QM a strategic issue for company owners; 2) involving customers in the improvement activities; and 3) developing processes that are robust, while still easily adaptable.Originality/Value: The Delphi study has identified upcoming challenges in the QM area based on input from 188 quality professionals.
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| 3. |
- Pang, Zhibo, et al.
(författare)
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An RTOS-based Architecture for Industrial Wireless Sensor Network Stacks with Multi-Processor Support
- 2013
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Ingår i: Proceedings ICIT 2013 - 2013 IEEE International Conference on Industrial Technology (ICIT). - 9781467345675 - 9781467345699 ; , s. 1216-1221
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Konferensbidrag (refereegranskat)abstract
- The design of industrial wireless sensor network (IWSN) stacks requires the adoption of real time operation system (RTOS). Challenges exist especially in timing integrity and multi-processor support. As a solution, we propose an RTOS-based architecture for IWSN stacks with multi-processor support. It offers benefits in terms of platform independency, product life cycle, safety and security, system integration complexity, and performance scalability. An implemented WirelessHART stack has proven the feasibility of the proposed architecture in practical product design. And future challenges as well as suggestions to standard improvement are discussed.
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| 4. |
- Wilkins, S. B., et al.
(författare)
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Resonant soft x-ray scattering investigation of orbital and magnetic ordering in La0.5Sr1.5MnO4
- 2005
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 71:24, s. 245102-
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Tidskriftsartikel (refereegranskat)abstract
- We report resonant x-ray scattering data of the orbital and magnetic ordering at low temperatures at the Mn L-2,L-3 edges in La0.5Sr1.5MnO4. The orderings display complex energy features close to the Mn absorption edges. Systematic modeling with atomic multiplet crystal field calculations was used to extract meaningful information regarding the interplay of spin, orbital, and Jahn-Teller order. These calculations provide a good general agreement with the observed energy dependence of the scattered intensity for a dominant orbital ordering of the d(x)(2)-z(2)/d(y)(2)-z(2) type. In addition, the origins of various spectral features are identified. The temperature dependence of the orbital and magnetic ordering was measured and suggests a strong interplay between the magnetic and orbital order parameters.
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