| 1. |
- Nilsson, Kristina, et al.
(författare)
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Plastic wave propagation in ductile slabs subjected to dynamic buckling
- 2003
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Ingår i: Mathematical Modelling in Physics, Engineering and Cognitive Science, v. 7. - 1651-0267. ; Mathematical Modelling of Wave Phenomena 2002, s. 207-215
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Konferensbidrag (refereegranskat)abstract
- Plastic wave propagation during dynamic buckling of ductile slabs is investigated numerically using a contour plot method (q-plot) showing contours of normalized effective plastic strain rate as a function of time and position. A non-linear finite element method is used to analyse the buckling problem of the elastic-viscoplastic slab. The contour plot method is quite sufficient to depict the overall development of the localization zones. Wave propagation speeds, relative growth of the localization zones and displacement of non-stationary in-elastic waves may be investigated. The present study also indicates that certain buckling modes may be promoted by selecting particular initial specimen geometries.
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| 2. |
- Dubaric, Ervin, et al.
(författare)
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Monte Carlo simulation of the response of a pixellated 3D photodetector in silicon
- 2002
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - 0168-9002 .- 1872-9576. ; 487:1-2, s. 136-141
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Tidskriftsartikel (refereegranskat)abstract
- The charge transport and X-ray photon absorption in three-dimensional (3D) X-ray pixel detectors have been studied using numerical simulations. The charge transport has been modelled using the drift-diffusion simulator MEDICI, while photon absorption has been studied using MCNP. The response of the entire pixel detector system in terms of charge sharing, line spread function and modulation transfer function, has been simulated using a system level Monte Carlo simulation approach. A major part of the study is devoted to the effect of charge sharing on the energy resolution in 3D-pixel detectors. The 3D configuration was found to suppress charge sharing much better than conventional planar detectors.
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| 3. |
- Henningsson, Börje
(författare)
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Det röda Dalarna : Socialdemokrater, anarkosyndikalister och kommunister inom Dalarnas Arbetarrörelse 1906-1937
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This dissertation investigates the internal struggles within the labour movement in Dalarna at the beginning of the twentieth century. I investigate Social Democracy, Anarcho-Syndicalism and Communism, the three major factions of the working class. I study the relationship between these organisations and their supporters in the complex socio-economic area of Dalarna.I have based my study on the three party programs and their answer to two central questions of the time: Will the conflicts of society lead to revolution? and How should politics and production be organised in the non capitalist society to come? Generally, anarcho-syndicalists argue that state power must be transformed to local government, social democrats hope to make different social interests compromise into political consensus. Communists want a proletarian state through social revolution. How were those ideologies received in Dalarna? In the beginning, anarchists fought social democrats: The opposition excluded from social democracy 1917 was also more influenced by anarchism than by communism. The opposition founded a party, witch towards the 1920´s turned from anarchism into communism, and the small farmers, that erlier had been attracted by the anarchist influenced rural propaganda, left and more industrial workers joined. Simultaneously, anarchists reorganised from a political party to a syndicalistic trade union, gradually mowing from the industrialised south to northern Dalarna. Communists, mainly left in the industrialised south, were shaken by two splits in the 1920´s and they lost their ability to compete with the social democrats in democratic elections. In Dalarna, social democrats, confronting anti-parliamentary anarchy and totalitarian communism alike, won the contest within the labour movement: At the end of the period, they dominated the area.
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| 4. |
- Hjelm, Mats, et al.
(författare)
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Monte Carlo simulation of the imaging properties of scintillator-coated X-ray pixel detetectors
- 2003
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - 0168-9002 .- 1872-9576. ; 509:1-3, s. 76-85
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Tidskriftsartikel (refereegranskat)abstract
- The spatial resolution of scintillator-coated X-ray pixel detectors is usually limited by the isotropic light spread in the scintillator. One way to overcome this limitation is to use a pixellated scintillating layer on top of the semiconductor pixel detector. Using advanced etching and filling techniques, arrays of CsI columns have been successfully fabricated and characterized. Each CsI waveguide matches one pixel of the semiconductor detector, limiting the spatial spread of light. Another concept considered in this study is to detect the light emitted from the scintillator by diodes formed in the silicon pore walls. There is so far no knowledge regarding the theoretical limits for these two approaches, which makes the evaluation of the fabrication process difficult. In this work we present numerical calculations of the signal-to-noise ratio (SNR) for detector designs based on scintillator-filled pores in silicon. The calculations are based on separate Monte Carlo (MC) simulations of X-ray absorption and light transport in scintillator waveguides. The resulting data are used in global MC simulations of flood exposures of the detector array, from which the SNR values are obtained. Results are presented for two scintillator materials, namely CsI(Tl) and GADOX.
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| 5. |
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| 6. |
- Karis, O, et al.
(författare)
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Probing surface states of Cu/Ni thin films using x-ray absorption spectroscopy
- 2001
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 63:11
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Tidskriftsartikel (refereegranskat)abstract
- Surface and interface properties of Cu thin films (1–4 monolayers) deposited on Ni(100) have been extracted by means of x-ray absorption spectroscopy and analyzed in combination with ab initio density-functional calculations. An unoccupied Cu surface state is identified in an x-ray absorption spectra and studied as a function of film thickness. Experimental data is supported by calculations of the layer-resolved density of states and the results from this combined theoretical-experimental effort show that the surface state is almost entirely located on the atomic layer closest to the vacuum. Our results also indicate strong hybridization between unoccupied states at the Cu/Ni interface boundary.
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| 7. |
- Manuilskiy, Anatoily, et al.
(författare)
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Spectroscopy applications for the Medipix photon counting X-ray system
- 2004
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : ELSEVIER SCIENCE BV. - 0168-9002 .- 1872-9576. ; 531:1-2, s. 251-257
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Tidskriftsartikel (refereegranskat)abstract
- Since the Medipix system is a photon counting system, it is possible to use it as a spectroscopic device, which is sensitive to the energy of the incoming photons. The system can, for example, be used to achieve the spectrum of an unknown source. Since it is an imaging system, it can be useful for energy dependent scattering experiments. The factors limiting the spectroscopic resolution are source and channel noise and detector non-uniformity. A well-known method for correction non-uniformity is to use mono energetic source and a threshold adjustment. However, since the threshold calibration is energy dependent, its use for sources with wider energy range is limited. We have shown an easy method to create threshold calibration masks for different thresholds that include both detector and channel stationary influences with analysis of histograms of series of images. The model for histograms was created assuming a standard dental X-ray source, which allows finding mask-creating parameters like threshold range (Vth and Vthadj). This procedure can be performed for each energy of interest. Based on these arrays, mask files that narrowed the threshold distribution close to the theoretical limit, were prepared. The limit of the spectroscopic resolution for the system was measured by analysing histograms for series of flat images under identical conditions.
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| 8. |
- Norlin, Börje, et al.
(författare)
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Material recognition with the Medipix photon counting colour X-ray system.
- 2004
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 531:1-2, s. 265-269
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Tidskriftsartikel (refereegranskat)abstract
- An energy sensitive imaging system like Medipixl has proved to be promising in distinguishing different materials in an X-ray image of an object. We propose a general method utilising X-ray energy information for materialrecognition. For objects where the thickness of the materials is unknown, a convenient material parameter to identify is K = α1/α2, which is the ratio of the logarithms of the measured transmissions In(t1)/In(t2). If a database of the parameter K for different materials and energies is created, this method can be used for material recognition independent of the thickness of the materials. Series of images of an object consisting of aluminium and silicon were taken with different energy thresholds. The X-ray absorption for silicon and aluminium is very similar for the range 40-60 keV and only differs for lower energies. The results show that it is possible to distinguish between aluminium and silicon on images achieved by Medipixl using a standard dental source. By decreasing the spatial resolution a better contrast between the materials was achieved. The resolution of contrasts shown by the histograms was close to the limit of the system due to the statistical noise of the signal.
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| 9. |
- Rehn, Börje, 1967-
(författare)
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Musculoskeletal disorders and whole-body vibration exposure among professional drivers of all-terrain vehicles
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Musculoskeletal disorders are common among professional driver groups. Ergonomic risk factors at work are often suggested as causative, aggravating or preserving. The general aim with this thesis is to investigate the association between musculoskeletal disorders and physical exposure with special with special focus on whole-body vibration (WBV), among professional drivers of all-terrain vehicles (ATVs). Drivers of ATVs are expsosed to high magnitudes of WBV and shock. This thesis included drivers of forest machines, snowgroomers and snowmobiles. A cross-sectional study revealed that ATV drivers had an increased risk of musculoskeletal symptoms in the neck-shoulder and thoracic regions, even after adjusting for age, smoking habits and psychosocial stress. Prevalence rates were in the range of 1.5-2.9 (CI:1.2-5.2) compared to an age-matched group from the general population. No group of ATV drivers had a significantly increased risk of low back pain. Trend analysis showed no association between symptoms and exposure time. A clinical investigation of a subgroup found that it was for ATV drivers with neck pain to have assymetrical and focal neuropathies, pure or in mix with a nociceptive disorder, in the neck and upper extremities (47-79%), which was in contrast to referents with neck pain who had more nociceptive disorders (27% prevalence of neuropathy). Two studies measured characteristics of seated WBV exposure in forest machines (forwarders), snowgroomers and snowmobiles. The magnitudes of WBV in ATVs, measured and analyzed according to ISO 2631-1, were between 0.5-3.5 m/s2 (frequency weighted vector sum), which was considered high compared to limits suggested by the international standard ISO 2631-1 and the physical agent directive from the Euoropean Union (0.5 m/s2, rms). Drivers of ATVs were exposed to horizontally directed WBV and shocks. Non-neutral neck postures are ergonomic risk factors that occured infrequently and with short duration. The magnitude of seated WBV in forwarder vehicles varied substantiálly depending on model, terrain condition and driver. This may result in different conclusions regarding health risk assessments. The main conclusion from this thesis is that musculoskeletal symptoms and disorders in the neck and upper extremities, among drivers of ATVs, may be a result of long-time exposure to shock-type and horisozontally oriented seated WBV.
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| 10. |
- Rehn, Börje, et al.
(författare)
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Musculoskeletal symptoms among drivers of all-terrain vehicles
- 2002
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Ingår i: Journal of Sound and Vibration. - : Elsevier BV. - 0022-460X .- 1095-8568. ; 253:1, s. 21-29
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this cross-sectional study was to characterize the risk of experiencing musculoskeletal symptoms in the region of the neck, shoulders and upper and lower back for professional drivers of various categories of all-terrain vehicles and to assess the association between symptoms and duration of exposure to whole-body vibration (WBV) and shock from driving all-terrain vehicles. The study group consisted of 215 drivers of forest machines, 137 drivers of snowmobiles and 79 drivers of snowgroomers and a control group of 167 men randomly selected from the general population. The subjects were all from one of the four most northern counties in Sweden and they were all men. Musculoskeletal symptoms were assessed by use of a standardized questionnaire. In addition, the questionnaire held items about the driving time with all-terrain vehicles and a subjective estimation of exposure to unpleasant movements (shock, jolt, irregular sway). The job strain was measured according to Karasek's demands/control model. The prevalence ratios were adjusted for age, smoking and job strain. Among drivers, significantly increased prevalence ratios within the range of 1∂5–2·9 were revealed for symptoms from the neck–shoulder and thoracic regions during the previous year. None of the driver categories had a statistically significantly increased risk of low back pain. Forest vehicles were those most reported to cause unpleasant movements. In conclusion, drivers of all-terrain vehicles exhibit an increased risk of symptoms of musculoskeletal disorders in the neck–shoulder and thoracic regions. The increased risk is suggested to be related to physical factors such as exposure to whole-body vibration (WBV) and shock, static overload or extreme body postures. However, since symptoms of low back pain were not significantly increased, it appears that factors other than WBV would explain the occurrence of symptoms in the group of all-terrain drivers.
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