| 1. |
- Jarvid, Markus, 1985, et al.
(författare)
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Electrical Tree Inhibition by Voltage Stabilizers
- 2012
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Ingår i: Annual Report - Conference on Electrical Insulation and Dielectric Phenomena, CEIDP. - 0084-9162. ; , s. 605-608
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Konferensbidrag (refereegranskat)abstract
- Electrical treeing is one of the main degradation mechanisms in polymer dielectrics at highly divergent electric fields and can, if initiated, cause dielectric breakdown as soon as an electrical tree channel has bridged the insulation. One way of increasing resistance to electrical treeing is the addition of certain organic additives such as polycyclic aromatic compounds or benzophenone-like structures. These additives act as voltage stabilizers that are believed to capture high energy electrons and dissipate their energy, preventing degradation of the polymer matrix by the impact of “hot electrons”. In this study, a benzil type compound is evaluated as voltage stabilizer in a superclean cross-linked polyethylene compound used for high voltage cable applications. The stabilizing effect of the additives is measured using test objects of wire-plane electrode geometry in ramped AC voltage experiments. For determining tree initiation conditions, optical detection is used and correlated to voltage measurements. In this way, the initiation voltage of each single tree is determined. Results show that the investigated voltage stabilizer raises the electrical tree inception level significantly. The stabilizing effect is dependent on voltage ramp rate and using a lower ramp rate results in a more pronounced effect of the stabilizer.
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| 2. |
- Jarvid, Markus, 1985, et al.
(författare)
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Tailored Side-Chain Architecture of Benzil Voltage Stabilizers for Enhanced Dielectric Strength of Cross-Linked Polyethylene
- 2014
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Ingår i: Journal of Polymer Science, Part B: Polymer Physics. - : Wiley. - 1099-0488 .- 0887-6266. ; 52:16, s. 1047-1054
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Tidskriftsartikel (refereegranskat)abstract
- The synthesis and physico-chemical properties of seven benzil-type voltage stabilizers are reported. The benzil core is substituted with alkyl chains of different length that are linked to the benzil core via an ester, ether, or tertiary amine group. All additives can be melt-processed with low-density polyethylene (LDPE). Fourier-transform infrared spectroscopy confirms that benzil compounds are not affected by the LDPE cross-linking reaction induced by dicumyl peroxide. Moreover, a combination of gel content measurements, thermal analysis, and small-angle X-ray scattering indicates that the presence of benzil voltage stabilizers does not significantly alter the microstructure of cross-linked polyethylene (XLPE). Electrical tree inhibition experiments under high-voltage alternating current conditions show that all investigated additives substantially enhance the dielectric strength of the insulating material at a concentration of only 10 mmol kg−1. The highest improvement in dielectric strength, of more than 70% with respect to reference XLPE, is obtained with voltage stabilizers, which carry short (methyl) side chains that are linked to the benzil core via an ester or tertiary amine group.
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| 3. |
- Johansson, Anette, 1977, et al.
(författare)
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A Versatile System for Electrical Treeing Tests under AC and DC Stress Using Wire Electrodes
- 2011
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Ingår i: 8th International Conference on Insulated Power Cables, Jicable’11, 19 – 23 June 2011, Versailles - France.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- An alternative method to evaluate electrical treeing in solid dielectric materials is presented. Here the test sample utilises a wire electrode for creating the necessary high divergent electric field. This introduces a different preparation method and several of the disadvantages with the traditional needle sample can be avoided. Together with the test object a versatile test setup for both AC and DC measurements is illustrated. This alternative method has proven successful and an evaluation thereof as well as a comparative study between the two electrode systems is included.
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| 4. |
- Doedens, Espen, 1988, et al.
(författare)
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Effects of Inclusions of Oxidized Particles in XLPE on Treeing Phenomena
- 2012
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Ingår i: Annual Report - Conference on Electrical Insulation and Dielectric Phenomena, CEIDP. - 0084-9162. ; , s. 597-600
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Konferensbidrag (refereegranskat)abstract
- One issue with the use of crosslinked polyethylene (XLPE) insulation in high voltage power cables is the presence of oxidized particles. Oxidation may occur during production of polyethylene, during the extrusion and curing process used to produce XLPE cables, or in subsequent processes/operation of the cables. Oxidized particles are here referred to as organic contaminants. In the present study artificial organic contaminants were introduced in XLPE samples made for electrical treeing measurements. Instead of using the common needle-needle or needle-plane configuration, a wire-plane configuration was used. Organic contaminants have an increasing conductivity and permittivity as function of increasing degree of oxidation. These properties most probably give rise to local electric field enhancements in the material. The morphology of organic contaminants also differs from virgin XLPE, which probably cause bad adhesion between the XLPE matrix and the contaminants. A combination of these factors was found to affect the electrical performance of the insulation. Several different parameters, such as dry and wet ageing, as well as AC voltage and DC voltage stress, were included in the study.
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| 5. |
- Jakobsson, Joel, et al.
(författare)
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Elevated Concentrations of Neurofilament Light Chain in The Cerebrospinal Fluid of Bipolar Disorder Patients.
- 2014
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Ingår i: Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology. - : Springer Science and Business Media LLC. - 1740-634X. ; 39, s. 2349-2356
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Tidskriftsartikel (refereegranskat)abstract
- Bipolar disorder (BD) is characterized by mood swings between manic and depressive states. The etiology and pathogenesis of BD is unclear, but many of the affected cognitive domains, as well as neuroanatomical abnormalities, resemble symptoms and signs of small vessel disease. In small vessel disease, cerebrospinal fluid (CSF) markers reflecting damages in different cell types and subcellular structures of the brain have been established. Hence, we hypothesized that CSF markers related to small vessel disease may also be applicable as biomarkers for bipolar disorder. To investigate this hypothesis, we sampled CSF from 133 patients with bipolar disorder and 86 healthy controls. The concentrations of neurofilament light chain (NF-L), myelin basic protein (MBP), S100B, and heart-fatty acid binding protein (H-FABP) were measured in CSF and analyzed in relation to diagnosis, clinical characteristics, and ongoing medications. Hereby we found an elevation of the marker of subcortical axonal damage, NF-L, in bipolar subjects. We also identified positive associations between NF-L and treatment with atypical antipsychotics, MBP and lamotrigine, and H-FABP and lithium. These findings indicate axonal damage as an underlying neuropathological component of bipolar disorder, though the clinical value of elevated NF-L remains to be validated in follow-up studies. The associations between current medications and CSF brain injury markers might aid in the understanding of both therapeutic and adverse effects of these drugs.Neuropsychopharmacology accepted article peview online, 03 April 2014; doi:10.1038/npp.2014.81.
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| 6. |
- Jantunen, Ari, et al.
(författare)
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Beyond appearances - Do dynamic capabilities of innovative firms actually differ?
- 2012
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Ingår i: European Management Journal. - : Elsevier BV. - 0263-2373 .- 1873-5681. ; 30:2, s. 141-155
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Tidskriftsartikel (refereegranskat)abstract
- Dynamic capabilities are the higher-order capabilities needed for changing operational-level capabilities and learning in new domains, and thus they are critical for innovation activities. The aim of this study is to explore heterogeneity of dynamic capabilities in a comparative setting. We chose four innovative case firms representing a single industry, namely magazine publishing. The similarity of the cases provided a solid foundation for comparing their dynamic capabilities. Based on the results it seems that the practices comprising sensing capabilities are likely to be similar across firms within a single industry, while practices comprising seizing and reconfiguring types of capabilities may differ more between companies. Thus dynamic capabilities have both idiosyncratic and common features across an industry. These findings are relevant to practicing managers in that they illustrate that competing companies within the same industry tend to develop similar types of practices to match the changing requirement of the operating environment. Hence, managers should not be falsely comforted by the current situation within their firms, but proactively develop their unique capabilities to gain advantage over their competitors.
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| 7. |
- Jarvid, Markus, 1985, et al.
(författare)
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Evaluation of the Performance of Several Object Types for Electrical Treeing Experiments
- 2013
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Ingår i: IEEE Transactions on Dielectrics and Electrical Insulation. - 1558-4135 .- 1070-9878. ; 20:5, s. 1712-1719
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Tidskriftsartikel (refereegranskat)abstract
- A comparison of the efficiency of various types of object for studying the development of electrical trees in polymers is presented. Two types of newly developed wire-plane objects are investigated and compared with two versions of the traditionally used needle-needle objects. The two needle-needle objects are prepared according to ASTM standard and act as references, whereas the alternative objects rely on use of an ultra-thin tungsten wire (10 and 20 µm) in the test objects for providing the highly divergent electric stress. In one type of those object the wire extends from a semiconducting tab embedded in the tested material, while in the other type, the embedded wire is extended and connected externally by means of a copper tape. The comparison is made using cross linked polyethylene (XLPE) for the testing purposes. The wire type objects provide some promising advantages, including parallel formation of several electrical trees and an exposure of a larger material volume. Further advantages include the considerable simplification of both the manufacturing and the measuring procedures. Among the newly developed test objects, the one without the semiconducting tab is considered most advantageous as it allows for more accurate treeing initiation measurements at a lower voltage level. On the other hand the disadvantage is a formation of kinks on the wire that results from polyethylene shrink during sample preparation, which may yield some difficulties in correctly estimating the local field strength locally as well as straining the surrounding material. However the multitude of electric trees formed in each sample allows to easily discard the trees growing at such imperfections in following data analyses. Although finding a statistical method that makes good use of all the data poses a challenge, a suggested approach is presented.
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| 8. |
- Johansson, Anette, 1977, et al.
(författare)
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Analysis of Multiple Electrical Trees Incepted at Wire Electrode Test Object by Means of PD Detection
- 2013
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Ingår i: Proc. of Jicable HVDC'13 Seminar. ; , s. paper P06-
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Konferensbidrag (refereegranskat)abstract
- This paper introduces a method allowing characterisingthe growth of electrical trees in wire-plane electrodeobjects. By applying both electrical and opticalmeasurements the inception level and the number of treeswere analysed. It is shown that the results observedoptically closely resemble the electrically detected PDbehaviour, thus exhibiting a good correlation betweenboth the methods. This indicates a possibility for analysingelectrical treeing process in non-transparent materialsbased on the electrical measurement only and opens foran efficient approach in evaluating new materials for cableinsulation.
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| 9. |
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| 10. |
- Johansson, Anette, 1977-
(författare)
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Entrepreneurialism - an asset in financial crises : A study of Swedish magazine publishers’ approach to new business development
- 2011
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The media industry is working in a constant turbulence due to technological advancements in the way media content is produced, spread and consumed. The financial crisis came in the midst of this challenging business environment and was a hard blow for the whole industry. Developing creative and profitable products under such uncertain and difficult circumstances puts the usefulness of traditional strategic principles such as planning and forecasts in question. This paper discuss how Swedish magazine publishers approach new business development and presents preliminary results from a study of 246 decision makers in 130 Swedish magazine publishing firms. These findings show that they use a logic similar to that of entrepreneurs, a logic which is different from generally applied management theory. It is suggested that having this entrepreneurial approach helps decision makers in the magazine industry to handle uncertainty, induced by financial crises but also induced by the general technological development.
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| 11. |
- Johansson, Anette, 1977-, et al.
(författare)
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Magazine publishers approaching new media : Is it about what we do or how we think?
- 2011
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- New technology, such as Internet, mobile phones and more recently the new reading devices, have posed many new challenges for the magazine publishing industry for over a decade and will continue to do so. In this paper we explore commonalities among magazine publishers being in the forefront of integrating new media in their businesses. We approach this by combining two streams of management literature, namely capabilities and management cognition. Within the capabilities stream we focus on dynamic capabilities, ie. the routines and practices needed for learning about new domains, creating new asset combinations and building new capabilities in order to match market needs. Within the management cognition stream, we focus on the decision-making logic used; whether it is dominantly based on causal logic (predictive control) or effectual logic (non-predictive control). Hence, we explore both what the magazine publishers do and how they think about new media. A case study of four innovative magazine publishers in Sweden and Finland has been conducted including 33 in-depth interviews. Practices related to business development and the decision making logic behind them has been carefully analyzed to find differences and similarities between the studied firms. The findings increase our understanding of the relationship of capabilities and cognition in approaching new media, and provide important implications for media managers.
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| 12. |
- Johansson, Anette, 1977-, et al.
(författare)
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Magazine Publishers Embracing New Media : Exploring their capabilities and decision making logic
- 2012
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Ingår i: Journal of Media Business Studies. - : Informa UK Limited. - 1652-2354 .- 2376-2977. ; 9:2, s. 97-114
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Tidskriftsartikel (refereegranskat)abstract
- During the last decade, new technologies, such as the Internet, mobile phones and more recently the new reading devices, have posed new challenges for the magazine publishing industry and will continue to do so. Here we explore commonalities among magazine publishers in the forefront of integrating new media into their businesses. We approach this by combining two streams of management literature: dynamic capabilities and decision making. A case study of four innovative magazine publishers has been conducted where the practices related to business development and their underlying decision making logic have been analyzed.
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| 13. |
- Johansson, Anette, 1977-, et al.
(författare)
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Unpacking the Antecedents of Effectuation and Causation in a Corporate Context
- 2012. - 32
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Ingår i: Frontiers of Entrepreneurship Research. - Wellesley, Mass. : Babson College. - 0910897360
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Konferensbidrag (refereegranskat)abstract
- Effectuation and causation are important modes of entrepreneurial decision-making. In this paper, we extend the literature on effectuation into the corporate context. Based on extant theory concerning both individual decision-makers’ human capital and organizational-level characteristics, we develop and test hypotheses concerning the use of effectuation and causation in pursuing new opportunities in the magazine industry. Our results, based on the actions of 246 key decision-makers, show an inconsistent set of antecedents for causation and the four effectual logic principles. As such, our multi-level study helps to unravel some of the complexities of the choice of decision-making logics.
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| 14. |
- Johansson, Anette, 1977, et al.
(författare)
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Wire-Plane Electrode System for Electrical Tree Initiation Exposed to AC and DC Voltage Stress
- 2011
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Ingår i: The Proceedings of 17th International Symposium on High Voltage Engineering, s. C-025. - 9783800733644
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Electrical treeing in XLPE exposed to DC (of both polarities) and 50 Hz AC voltages has been analysed in a wire-plane electrode geometry using real-time optical detection and microscopic observations. It has been found that treeing mechanisms differ between AC and DC stresses. For AC voltage, the tree initiation and growth is easily observable in real time during the testing. In the case of DC stress a complete breakdown of the XLPE occurs before electrical trees can be discerned with the use of CCD camera. However, in the microscopic observations of the specimens, very fine tree structures can be distinguished. The effect of voltage ramping rate was also analysed. For AC stress, the faster ramping results in a higher tree inception voltage. The opposite trend is true for DC stress, where the faster ramp results in a lower breakdown voltage level. When comparing the effect on polarity of the DC breakdown voltage, negative polarity results in higher voltage levels than positive polarity.
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| 15. |
- Wikström, Patrik, et al.
(författare)
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Publishing
- 2013
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Ingår i: Handbook on the digital creative economy. - Cheltenham, UK : Edward Elgar Publishing. - 978 1 78100 486 9
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Bokkapitel (refereegranskat)
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