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| 2. |
- Dewi, Handika Sandra, et al.
(författare)
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Microstructure and mechanical properties of laser surface treated 44MnSiVS6 microalloyed steel
- 2020
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Ingår i: Optics and Laser Technology. - : Elsevier. - 0030-3992 .- 1879-2545. ; 127
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Tidskriftsartikel (refereegranskat)abstract
- Fatigue property improvement for automotive components such as crankshafts can be achieved through material selection and tailored surface design. Microalloyed steels are of high interest for automotive applications due to their balanced properties, excellent hardenability and good machinability. Lasers facilitate efficient and precise surface processing and understanding the laser-material-property interrelationships is the key to process optimisation. This work examines microstructural development during laser surface treatment of 44MnSiVS6 microalloyed steel and the resulting mechanical properties. Laser beam shaping techniques are employed to evaluate the impact of beam shaping on the process. It revealed that ferrite structures remain in the treated area surrounded by martensite due to insufficient heating and dwell time of carbon diffusion.
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| 3. |
- Fischer, Andreas, et al.
(författare)
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A pragmatic approach for assessment of laser-induced compressive residual stress profiles
- 2021
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Ingår i: Journal of Manufacturing Processes. - : Elsevier. - 1526-6125 .- 2212-4616. ; 68, part A, s. 778-787
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Tidskriftsartikel (refereegranskat)abstract
- Laser hardening is a very efficient technique for local surface treatment, however, in case of complex and large components robust processing is highly challenging due to limitations in terms of the absolute size of the overall heat-affected zone. As is shown in the present work, an increased in-depth effect can be achieved by tailoring the laser parameters without melting the surface layer. Optimization of process parameters leads to an elaborate test design demanding numerous verification measurements to determine essential material properties. In this context, the evaluation of compressive residual stress values in the surface layer is very important, e.g. in case of fatigue loaded components. However, residual stress profile measurements obtained by X-ray diffraction are very time-consuming and, thus, can significantly impair the laser parameter development cycle. For this reason, the present study introduces a novel pragmatic approach allowing for qualitative evaluation of laser-induced compressive residual stress states, in particular for multiple laser pass processes based on a Gaussian-like intensity profile. Based on straightforward analytical evaluation, several characteristic features of the affected surface layer, e.g. the position of the residual stress transition zone, can be correlated to a change of the local energy input. A novel parameter referred to as modified area energy is established in present work for this purpose. This novel energy approach provides for an essential contribution to the field of laser hardening to considerably shorten the experimental effort within the laser parameter search.
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| 4. |
- Fischer, Carolyn, et al.
(författare)
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A bio-economic model of community incentives for wildlife management under CAMPFIRE
- 2011
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Ingår i: Environmental and Resource Economics. - : Springer Science and Business Media LLC. - 0924-6460 .- 1573-1502. ; 48:2, s. 303-319
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Tidskriftsartikel (refereegranskat)abstract
- This paper formulates a bio-economic model to analyze community incentives for wildlife management under benefit-sharing programs like the Communal Areas Management Programme for Indigenous Resources (CAMPFIRE) in Zimbabwe. Three agents influence the wildlife stock: a parks agency determines hunting quotas, outside poachers hunt illegally, and a local community may choose to protect wildlife by discouraging poaching. Wildlife generates revenues from hunting licenses and tourism; it also intrudes on local agriculture. We consider two benefit-sharing regimes: shares of wildlife tourism rents and shares of hunting licenses. Resource sharing does not necessarily improve community welfare or incentives for wildlife conservation. Results depend on the exact design of the benefit shares, the size of the benefits compared with agricultural losses, and the way in which the parks agency manages hunting quotas
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| 5. |
- Fischer, Tobias, et al.
(författare)
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Core collapse supernovae in the QCD phase diagram
- 2012
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Ingår i: Physics of Atomic Nuclei. - 1063-7788 .- 1562-692X. ; 75:5, s. 613-620
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Tidskriftsartikel (refereegranskat)abstract
- We compare two classes of hybrid equations of state with a hadron-to-quark matter phase transition in their application to core collapse supernova simulations. The first one uses the quark bag model and describes the transition to three-flavor quark matter at low critical densities. The second one employs a Polyakov-loop extended Nambu-Jona-Lasinio (PNJL) model with parameters describing a phase transition to two-flavor quark matter at higher critical densities. These models possess a distinctly different temperature dependence of their transition densities which turns out to be crucial for the possible appearance of quark matter in supernova cores. During the early post-bounce accretion phase quark matter is found only if the phase transition takes place at sufficiently low densities as in the study based on the bag model. The increase critical density with increasing temperature, as obtained for our PNJL parametrization, prevents the formation of quark matter. The further evolution of the core collapse supernova as obtained applying the quark bag model leads to a structural reconfiguration of the central protoneutron star where, in addition to a massive pure quark matter core, a strong hydrodynamic shock wave forms and a second neutrino burst is released during the shock propagation across the neutrinospheres. We discuss the severe constraints in the freedom of choice of quark matter models and their parametrization due to the recently observed 2M ⊙ pulsar and their implications for further studies of core collapse supernovae in the QCD phase diagram.
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| 6. |
- Jongeling, Rogier, et al.
(författare)
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Quantitative analysis of workflow, temporary structure usage, and productivity using 4D models
- 2008
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Ingår i: Automation in Construction. - : Elsevier BV. - 0926-5805 .- 1872-7891. ; 17:6, s. 780-791
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents time-space analyses of construction operations supported by quantitative information extracted from 4D CAD models. The application of 4D models is a promising approach to help introduce construction innovations and to evaluate construction alternatives. Current analyses of 4D models are mainly visual and provide project stakeholders with a clear, but limited, insight of construction planning information. This practice does not take advantage of the quantitative data contained in 4D models. We use two 4D models of an industry test case to illustrate how to analyze, compare, and present 4D content quantitatively (i.e., workspace areas, work locations, and distances between concurrent activities). This paper shows how different types of 4D content can be extracted from 4D models to support 4D-content-based analyses and novel presentation of construction planning information. We suggest further research aimed at formalizing the contents in 4D models to enable comparative quantitative analyses of construction planning alternatives. Formalized 4D content can enable the development of reasoning mechanisms that automate 4D-model-based analyses and provide the data content for presentations of construction planning information.
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| 7. |
- Jongeling, Rogier, et al.
(författare)
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Quantitative analysis using 4D models : an explorative study
- 2005
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Ingår i: First International Conference on Construction Engineering and Management. - : Korea Institute of Construction Engineering and Management. ; , s. 830-835
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Konferensbidrag (refereegranskat)
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| 8. |
- Milz, Mathias, et al.
(författare)
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Retrieval of water vapour in the upper troposphere/lower stratosphere from mipas envisat limb emission spectra
- 1999
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Ingår i: Proceedings of SPIE, the International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 3756, s. 536-543
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Tidskriftsartikel (refereegranskat)abstract
- Global Measurements of water vapor in the upper troposphere and lower stratosphere (UT/LS) are required to assess its influence on the radiation budget of the Earth and for its use as a suitable tracer for the study of troposphere-stratosphere exchange processes(STE). MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) is a Fourier transform spectrometer measuring limb emission spectra. The field of view of the satellite-borne MIPAS/Envisat is rather wide compared to horizontal and vertical structures in real water vapor distributions (e.g. hygropause). Our aim is to derive UT/LS water vapor profiles from MIPAS/Envisat data with optimized spatial resolution and accuracy. The retrieval errors and vertical resolution were assessed in an altitude- range 5 - 25 km with respect to a MIPAS standard observation scenario and the retrieval of the water vapor profile to be performed on the measurement grid. As target parameters we used water vapor and continuum in the first case and water vapor, temperature and continuum in the second scenario. Improvements by joint retrieval of water vapor and temperature are investigated, in particular for saturated H2O- signatures originating fromthe troposphere. The vertical resolution was estimated by the use of so-called averaging kernels.
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| 9. |
- Orosz, Katalin, et al.
(författare)
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Crack development and deformation behaviour of CFRP-reinforced mortars
- 2013
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Ingår i: Nordic Concrete Research. - 0800-6377. ; 48, s. 49-69
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports on a research study investigating CFRPreinforced mortars in uniaxial tension, as a strengthening material for concrete structures. The bare strengthening material was tested on dogbone specimens. Crack formation, crack development and the interaction between the grid and the mortar phase with varying geometrical parameters and mortar compositions have been investigated and evaluated. The use of engineered cementitious composites, exhibiting multiple cracking and enhanced pseudo-ductility in uniaxial tension, was found to result in an improved overall performance.
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| 10. |
- Orosz, Katalin, et al.
(författare)
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From material level to structural use of mineral-based composites : An overview
- 2010
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Ingår i: Advances in Civil Engineering / Hindawi. - : Hindawi Limited. - 1687-8086 .- 1687-8094. ; 2010
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Tidskriftsartikel (refereegranskat)abstract
- This paper surveys different material combinations and applications in the field of mineral-based strengthening of concrete structures. Focus is placed on mechanical behaviour on material and component levels in different cementitious composites; with the intention of systematically maping the applicable materials and material combinations for mineral-based strengthening. A comprehensive description of a particular strengthening system developed in Sweden and Denmark, denominated as Mineral-based Composites (MBCs), together with tests from composite material properties to structural elements is given. From tests and survey it can be concluded that the use of mineral-based strengthening system can be effectively used to increase the load bearing capacity of the strengthened structure. The paper concludes with suggestions on further development in the field of mineral-based strengthening
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