| 1. |
- Angenendt, Knut, 1982, et al.
(författare)
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Ionic liquid structures from large DFT calculations using mindless configurations
- 2010
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 114:48, s. 20577-20582
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Tidskriftsartikel (refereegranskat)abstract
- Three different popular imidazolium based ionic liquids (ILs); EMI-BF4, EMI-PF6, and EMI-TFSI, have been modeled by DFT calculations (B3LYP/6-311+G*) using large, up to 130 atom cluster models, for a better understanding of the structure and ion ion interactions in these ILs and ILs in general. Particular emphasis has been put on the role of appropriate starting structures and how the present large models differ from the ion-pair models of ILs generally used. The system size normalized ion ion interaction energies are shown to converge rapidly, and conformational equilibria and higher order properties like IR spectra are shown to be valuable as quality criteria. The explicit inclusion of an IL environment by the large cluster approach is also compared to using an implicit, continuum, strategy via SCRF C-PCM calculations.
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| 2. |
- Cherednichenko, Serguei, 1970, et al.
(författare)
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Online Detection of H2O and CO in the Humid Raw Gas from the Gasifier Using Terahertz Spectroscopy
- 2013
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Ingår i: ICPS, 13 International Conference on Polygeneration Strategies, Sept.5-13, Vienna, Austria. - 9783950275483 ; , s. 51-58
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Konferensbidrag (refereegranskat)abstract
- The integration of a gasifier with a complex multistage synthesis process, such as SNG synthesis, demands a fast monitoring of the gasifier performance. However, despite the availability of standard analyzers for determination of dry gas composition, there are still many practical difficulties remaining in the online measurement of tar and steam in the raw gas. For the detection of steam concentration, electromagnetic waves at terahertz frequencies (102-104 GHz) are promising with regard to development of a robust online measurement device for industrial application. The main reason for the high potential is the low risk for interference with the wide range of other molecules and that the transmission of electromagnetic waves at THz frequencies is rather low sensitive to deposits and particulate matter in the course of the beam compared to the conventional and well established wavelengths like infrared. In the present work, a THz gas spectrometer was designed and constructed to check the feasibility of applying this measurement technique at industrial scale. For this purpose, continuous flows of raw gas with various water and CO contents from the Chalmers gasifier as well as a flue gas with known water content from the biomass combustor were introduced to the spectrometer set-up. H2O and CO compositions in each stream were determined in an online manner. The results confirmed the possibility of applying strong rotational water lines at 448 and 380 GHz to develop reliable devices for online measurement of water vapor with excellent error interval. However, some difficulties were encountered for simultaneous detection CO concentration with water within the frequency range studied in this work (300-500 GHz).
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| 3. |
- Chernikova, Dina, 1982, et al.
(författare)
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Development of the Neutron-Gamma-Neutron (NGN) approach for the fresh and spent fuel assay
- 2012
-
Ingår i: Proceedings of The 53nd Annual Meeting of the Institute of Nuclear Materials Management.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In connection with current safety and complexity limitations for installations which usekeV neutrons for irradiation in the fresh and spent fuel assay, in medicine, geophysicaland detection fields, there is a long felt need of effective, light, inexpensive systems withlonger lifetimes and the possibility to ”switch off” the source during transportation andwork break. The present paper discusses an opportunity of creating a novel technique basedon using a pulsed neutron generator, hydrogen moderator and beryllium, which will enablecreation of a compact and inexpensive facility capable to satisfy all requirements. The mainidea of the proposed method consists in using photonuclear reaction in beryllium due togamma irradiation originating from (n,gamma) reaction in a hydrogen containing moderator.After the neutron pulse of a modern compact DD neutron generator in hydrogen-containingmoderator, high-energy neutrons (approximately 2.5 MeV) get slowed down mainly by elasticscattering to near thermal energies. At thermal energies, the neutrons diffuse through thematerial until they undergo thermal capture (capture is dominated by hydrogen neutronabsorbers). When a hydrogen atom captures a thermal neutron, it turns into deuteriumwith the release of a large component of 2.23 MeV gamma-rays. Beryllium is one of thefew elements in nature that undergoes a photonuclear reaction with this gamma energyrange (e.g. deuterium has a low energy 2.225 MeV photonuclear threshold). Thus, as theberyllium has lower neutron-binding energy, 1.667 MeV (photonuclear reaction threshold),a photonuclear reaction will take place with emission of neutrons with energy defined by thekinematic equation. Thus, this method allows to obtain a high quality epithermal neutronbeam without using a complex system with particle accelerator or radioisotope sources withlimited decay time. The proposed method has been studied using Monte Carlo simulations,which made it possible to define the theoretical limits of the use of the NGN approach inindustrial applications. The paper will presents the results of these investigations.
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| 4. |
- Chernikova, Dina, 1982, et al.
(författare)
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Testing a direct method for evaluating the concentration of boron in a fuel pool using scintillation detectors, and a 252Cf and an 241Am-Be source
- 2013
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Ingår i: Proceeding of ESARDA meeting 2013.
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Konferensbidrag (refereegranskat)abstract
- The present investigations are aimed at the development and testing of a direct non-destructive method for evaluating the concentration of boron in a fuel pool using scintillation detectors. The method uses a modified ratio between two gamma lines with energy of 480 keV and 2.23 MeV. These lines belong to the capture of a thermal neutron in boron and hydrogen, respectively. The relation between them can reveal the concentration of boron in the fuel pond.The method proposed was tested in a laboratory experiment with a 252Cf and an 241Am-Be source. EJ-309 liquid scintillation detectors were used for measurements of gamma spectra. The concentration of boron in water varied from 1550 ppm to 4200 ppm. The optimization and test studies were performed via MCNPX simulations.The results of these tests are provided in the present paper and they show that the boron content in water can be determined through using the characteristics of gamma lines with energy of 480 keV and 2.23 MeV.
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| 5. |
- Dufek, Jan, 1978
(författare)
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Building the nodal nuclear data dependences in a many-dimensional state-variable space
- 2011
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Ingår i: Annals of Nuclear Energy. - : Elsevier BV. - 0306-4549 .- 1873-2100. ; 38:7, s. 1569-1577
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Tidskriftsartikel (refereegranskat)abstract
- We present new methods for building the polynomial-regression based nodal nuclear data models. Thedata models can reflect dependences on a large number of state variables, and they can consider varioushistory effects. Suitable multivariate polynomials that approximate the nodal data dependences are identifiedefficiently in an iterative manner. The history effects are analysed using a new sampling scheme forlattice calculations where the traditional base burnup and branch calculations are replaced by a largenumber of diverse burnup histories. The total number of lattice calculations is controlled so that the datamodels are built to a required accuracy.
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| 6. |
- Dufek, Jan, 1978-
(författare)
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Complex models of nodal nuclear data
- 2011
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Ingår i: International Conference on Mathematics and Computational Methods Applied to Nuclear Science and Engineering (M&C 2011). - 9788563688002
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Konferensbidrag (refereegranskat)abstract
- During the core simulations, nuclear data are required at various nodal thermal-hydraulic and fuel burnup conditions. The nodal data are also partially affected by thermal-hydraulic and fuel burnup conditions in surrounding nodes as these change the neutron energy spectrum in the node. Therefore, the nodal data are functions of many parameters (state variables), and the more state variables are considered by the nodal data models the more accurate and flexible the models get. The existing table and polynomial regressionmodels, however, cannot reflect the data dependences on many state variables. As for the table models, the number of mesh points (and necessary lattice calculations) grows exponentially with the number of variables. As for the polynomial regression models, the number of possible multivariate polynomials exceeds the limits of existing selection algorithms that should identify a few dozens of the most important polynomials. Also, the standard scheme of lattice calculations is not convenient for modelling the data dependences on various burnup conditions since it performs only a single or few burnup calculations at fixed nominal conditions. We suggest a new efficient algorithm for selecting the most important multivariate polynomials for the polynomial regression models so that dependences on many state variables can be considered. We also present a new scheme for lattice calculations where a large number of burnup histories are accomplished at varied nodal conditions. The number of lattice calculations being performed and the number of polynomials being analysed are controlled and minimised while building the nodal data models of a required accuracy.
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| 7. |
- Frennert, Susanne, PhD, et al.
(författare)
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Using attention cards to facilitate active participation in eliciting old adults' requirements for assistive robots
- 2013
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Ingår i: IEEE International Workshop on Robot and Human Interactive Communication. - : IEEE conference proceedings. - 9781479905072 ; , s. 774-779, s. 774-779
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Konferensbidrag (refereegranskat)abstract
- Engaging old users in the exploration of future product concepts can be challenging. It is of great value to find ways to actively involve them in the design of novel technologies intended for them, particularly when they have no prior experience of the technology in question. One obstacle in this process is that many old people do not identify themselves as being old or they think that it (the technology) would be good for others but not themselves. This paper presents a card method to overcome this obstacle. A full-day workshop with three internal focus groups was run with 14 participants. Based on our experience, we propose a way in which active participation in the process of eliciting user requirements for assistive robots from old users with no prior experience of assistive robots can be carried out.
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| 8. |
- Huang, L., et al.
(författare)
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Anomalous temperature dependence of elastic constant c(44) in V, Nb, Ta, Pd, and Pt
- 2010
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Ingår i: Journal of Physics and Chemistry of Solids. - : Elsevier BV. - 0022-3697 .- 1879-2553. ; 71:8, s. 1065-1068
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Tidskriftsartikel (refereegranskat)abstract
- The anomalous temperature dependence of elastic constant c(44) for elements V. Nb, Ta, Pd, and Pt, has been calculated using first-principles theory. It is shown that the variation of elastic constant for simple elements can be approximated as the sum of thermal expansion and electronic components. The thermal expansion contributes the normal linearly decreasing effect to the elastic constant with temperature, while electronic contribution is determined by the unique character of electronic structure of elements and leads to the anomalous effect to the elastic constant with temperature.
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| 9. |
- Insulander Björk, Klara L, 1982
(författare)
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Thorium-plutonium fuel for long operating cycles in PWRs - preliminary calculations
- 2012
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Ingår i: Proceedings of the Thorium and Rare Earths Conference.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Preliminary calculations have been carried out to investigate the possibility of extending oper-ating cycle length in PWRs by use of Thorium-Plutonium mixed oxide fuel (Th-MOX). Thecalculations have been carried out in two dimensions, using the fuel assembly burnup simula-tion program CASMO-5. The reload scheme and the operating parameters are modelled on theSwedish PWR Ringhals 3 and a normal UOX fuel assembly designed for this reactor has beenused as a reference. Results show that an extension of the currently employed 12-month oper-ating cycle length is possible, either with a burnable absorber or with a modified fuel assemblydesign, assuming the same 3-batch reload scheme as currently used in Ringhals 3.The initial k∞ of the new Th-MOX fuel design was designed not to exceed that of the refer-ence UOX fuel. The power peaking factor is initially significantly lower than the reference,but slightly higher later in the life of the fuel assembly. All reactivity coefficients are withinacceptable range. The worth of control rods and soluble boron are lower than the reference, asexpected for a plutonium-bearing fuel.
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| 10. |
- Jagtap, Santosh, et al.
(författare)
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Design for the BOP and TOP markets: Strategies used by the design students
- 2013
-
Konferensbidrag (refereegranskat)abstract
- The base (BOP) and the top (TOP) of the world income pyramid represent the poor people and the people from developed countries, respectively. About two-fifths of the world population can be categorized as poor. Poverty is a trap because children born to poor parents are likely to grow up to be poor adults. In recent years, a poverty reduction approach that combines business development with poverty alleviation has received attention. The design of products for the BOP is an important ingredient of this poverty reduction approach. While companies are beginning to address the product needs of the BOP, there is limited practical and theoretical knowledge to support them. The current understanding of the design for the BOP is limited. This study aims at exploring the differences between the design strategies used by the industrial design students in designing products for the BOP and TOP markets. The results indicate the differences between their design strategies (i.e. problem driven strategy, solution driven strategy) in designing products for the BOP and TOP markets. We have discussed the implications of the findings for design practice and education. In particular, we have discussed how university-based design projects for the BOP can help in developing students’ different design skills.
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