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- Pettersson, Patrik, et al.
(author)
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Method for measuring permeability of pulp suspension at high basis weights
- 2008
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In: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 34:4, s. 191-197
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Journal article (peer-reviewed)abstract
- During the formation of pulp to paper, a large amount of water is added to dilute the pulp in order to obtain a homogenous material. This water call be mechanically and/or thermodynamically removed by different process solutions. The pulp suspension flows through various process equipment that influence the pulp suspension by changing its properties before the pulp suspension finally becomes paper. It is important to understand the mechanisms behind the transport path of water in this process in order to reduce cost and to increase the production rate of pulp and paper. The resistance to flow must be known in order to describe the flow path and the corresponding pressure drop in dewatering equipment in a pull.? mill. For networks with a complex geometry, a reliable method is to measure the resistance to flow at discrete points and to fit suitable resistance models to the results obtained. The objective of this study is to investigate how the history of pulp suspensions affects their permeability. A device for measuring the permeability of various pulp suspensions at high basis weights is developed and validated. Then the permeability of a number of virgin pulp species is measured. Some of the suspensions are then circulated in a closed flow loop and permeability is measured as a function of the number of loops. The results from two separate test's show that a basis weight variation and a different process treatment of the pulp suspension do not influence permeability.
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| 3. |
- Andersson, Anders G., et al.
(author)
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Flow through a two-scale porosity material
- 2009
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In: Research Letters in Materials Science. - : Hindawi Limited. - 1687-6822 .- 1687-6830.
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Journal article (other academic/artistic)abstract
- Flow through a two-scale porous medium is here investigated by a unique comparison between simulations performed with computational fluid dynamics and the boundary element method with microparticle image velocimetry in model geometries.
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| 6. |
- Lundin, Joakim, 1978-, et al.
(author)
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Analysis of four-wave mixing of high-power lasers for the detection of elastic photon-photon scattering
- 2006
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In: Physical Review A. Atomic, Molecular, and Optical Physics. - : The American Physical Society. - 1050-2947 .- 1094-1622. ; 74:4, s. 043821-043831
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Journal article (peer-reviewed)abstract
- We derive expressions for the coupling coefficients for electromagnetic four-wave mixing in the nonlinear quantum vacuum. An experimental setup for detection of elastic photon-photon scattering is suggested, where three incoming laser pulses collide and generate a fourth wave with a new frequency and direction of propagation. An expression for the number of scattered photons is derived and, using beam parameters for the Astra Gemini system at the Rutherford Appleton Laboratory, it is found that the signal can reach detectable levels. Problems with shot-to-shot reproducibility are reviewed, and the magnitude of the noise arising from competing scattering processes is estimated. It is found that detection of elastic photon-photon scattering may be achieved.
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| 9. |
- Lundström, E., et al.
(author)
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Using high-power lasers for detection of elastic photon-photon scattering.
- 2006
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In: Physical Review Letters. - : The American Physical Society. - 0031-9007 .- 1079-7114. ; 96:8, s. 083602-083605
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Journal article (peer-reviewed)abstract
- The properties of four-wave interaction via the nonlinear quantum vacuum is investigated. The effect of the quantum vacuum is to generate photons with new frequencies and wave vectors, due to elastic photon-photon scattering. An expression for the number of generated photons is derived, and using state-of-the-art laser data it is found that the number of photons can reach detectable levels. In particular, the prospect of using the high-repetition Astra Gemini system at the Rutherford Appleton Laboratory is discussed. The problem of noise sources is reviewed, and it is found that the noise level can be reduced well below the signal level. Thus, detection of elastic photon-photon scattering may for the first time be achieved.
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| 10. |
- Nilsson, T, et al.
(author)
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Thermal perception thresholds among young adults exposed to hand-transmitted vibration
- 2008
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In: International Archives of Occupational and Environmental Health. - Berlin : Springer. - 0340-0131 .- 1432-1246. ; 81:5, s. 519-533
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Journal article (peer-reviewed)abstract
- Introduction: Quantitative sensory testing assesses non-invasively the function of the sensory pathways from receptors to cortex. Studies of workers exposed to vibration support evidence that neuro-sensory hand-arm vibration syndrome also encompasses neuropathy of the small-diameter nerve fibres. OBJECTIVES: To assess the risk of disturbed thermal perception developing among young adults exposed to vibration and hand-intensive manual work. The aim also encompasses the study of alternative covariates in small-diameter nerve fibre neuropathy assessment. Methods: This cross-sectional multi-centre study comprised 202 males and females from vocational school programs in auto mechanics, construction and catering. The testing included a baseline questionnaire, a clinical examination focusing on upper extremity disorders and quantitative somatosensory testing. Thermal perception thresholds were assessed, on both hands, second and fifth digits, using a modified Marstock method for warmth and cold. Results: Reduced thermal perception sensitivity was found for digit II compared to digit V, for females compared to males, and between the two study centres. Subjects exposed to vibration at work showed reduced sensitivity to temperature compared to non-vibration exposed. In univariate analyses odds ratios of 1.06 (95% CI 1.006-1.118) and 1.02 (95% CI 0.971-1.078) for reduced perception to cold for the right and left hands, respectively, was found for vibration. This association was lost in multivariate analyses. The study centre was the strongest confounding influence. Conclusions: Sensitivity to temperature appears to be reduced despite the subjects short exposure-time and low exposure to vibration. The effect is small in relation to other confounding factors. A low agreement between the modalities indicates the need for separate tests for cold and warmth. Hand-side, age, stature, and BMI were not important for thermal perception but study centre, gender and choice of digit were. Conventional electro-diagnostic investigations are inadequate for evaluating the status of the small-fibre afferent systems leaving QST of thermal perception as the preferred diagnostic tool.
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