| 51. |
- Wågberg, Lars-Göran, et al.
(författare)
-
Litteraturstudie av däckdubbars effekt på vägslitage, väglag, trafiksäkerhet och miljö
- 2004
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Detta notat är en sammanställning av en litteraturstudie av effekter av dubbdäcksanvändning. Studerade effekter omfattar slitage friktion, väglag, säkerhet och miljö. Studien har genomförts under kort tid, ungefär en månad, vilket innebär att den inte kunnat bli fullständig och heltäckande. Värdering av effekter har inte ingått i studien. Studien har alltså haft begränsad omfattning och värdering av effekter har inte kartlagts. Det medför att det inom ramen för denna studie inte finns utrymme för att genomföra en analys av olika åtgärder för att minska dubbdäcksanvändningen.
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| 52. |
- Wågberg, Lars-Göran
(författare)
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Pavement deterioration : Crack initiation and crack propagation models
- 2002. - 1
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Ingår i: Bearing Capacity Of Roads Railways and Airfields. - London : CRC Press. - 9781000108101 - 9789058093967 ; , s. 549-560
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The objective of the study presented here was to develop models for predicting the cumulative number of load applications to the initiation of cracking for flexible pavements and to develop models for predicting crack propagation in flexible pavements. Crack initiation is defined as the first appearance of cracking in the wheel paths. The models are aimed for use in Pavement Management Systems. Data used in the study consists of data from a Swedish LTPP (Long-Term Pavement Performance) study where over 600 test sections have been monitored during more than ten years. Every year a detailed distress survey and measurements of rut depth and the longitudinal profile has been carried out at each test section. The database contains information about traffic, climate, pavement structure, surface condition and structural strength. Pavement response based explanatory factors included, among other things, tensile strain at the bottom of the asphalt layer and other deflection based factors (i.e. surface curvature index, curvature basin factor, bearing capacity). The modelling of crack initiation models was carried out using a survival analysis approach. The results showed that data came from a Weibull distribution with an increasing risk of failure as pavement age increases. The modelling of crack propagation models was carried out using linear regression analysis. From the data, describing the yearly development of cracks, a Cracking Index was calculated. The same approach of developing crack models was used in the PARIS (Performance analysis of road infrastructure) project carried out within the 4th European Framework Programme Road Transport 1996-1998. Models were successfully developed to predict the cumulative number of traffic loadings to the initiation of cracking in the wheel paths. The models included two independent variables to pavement response and ageing (a relationship between a response variable and the annual cumulative number of traffic loadings). As response variables Surface Curvature Index 300 or Tensile Strain at the bottom of the asphalt layer can be used in the crack initiation models. Models were also developed to predict crack propagation in the wheel paths. For any given section of road, the slope of the linear model can be estimated from the level of distress at the last distress survey and the age of the pavement surface or the number of ESALs carried by the pavement at that time. All models have been validated against independent data, not used in the development phase.
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| 53. |
- Wågberg, Lars-Göran
(författare)
-
Utveckling av nedbrytningsmodeller : sprickinitiering och sprickpropagering
- 2001
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Målsättningen i detta projekt har varit att utveckla tillståndsförändringsmodeller för initiering av belastningsbetingade sprickor i och omedelbart utanför hjulspåren samt modeller som beskriver med vilken hastighet dessa sprickor därefter propagerar. De modeller som tagits fram i projektet är avsedda att användas i så kallade PM-system (Pavement Management) eller system för under- hållsplanering på ren svenska. Informationen om hur våra vägar är uppbyggda, vilka material som använts, materialens egenskaper etc är mycket knapphändig och kan därför inte utgöra indata i modeller av detta slag. All data som utgör underlag för modellutvecklingen har hämtats från det svenska nationella LTPP-projektet (Long Term Pavement Performance) som VTI har drivit på uppdrag av Vägverket under många år. Det är helt avgörande att modeller av detta slag utvecklas med hjälp av högkvalitativa och representativa data. Sveriges medverkan i PARIS-projektet (Performance Analysis of Road Infrastructure, European Commission 1998) har visat att data från det svenska LTPP-projektet håller hög kvalitet.Indata till de sprickinitieringsmodeller som har utvecklats i projektet är antingen Surface Curvature Index 300 (SCI300) eller töjningen i underkant av asfaltlagren (STRAIN) samt antalet ekvivalenta standardaxlar (N100) per år. SCI300 respektive STRAIN beräknas utifrån fallvikts- data.Indata till de sprickpropageringsmodeller som utvecklats är antingen antalet ackumulerade ekvivalenta standardaxlar (N100) eller ackumulerat antal år sedan senaste beläggningsåtgärd vid besiktningstillfället samt sprickindex vid aktuellt besiktningstillfälle.
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| 54. |
- Wågberg, Lars, et al.
(författare)
-
Kinetics of polyelectrolyte adsorption on cellulosic fibers
- 2001
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 17:4, s. 1096-1103
-
Tidskriftsartikel (refereegranskat)abstract
- The present investigation has been focused on studying the adsorption of three different molecular mass fractions of a polydimethyldiallylammonium chloride (DMDAAC) (8750 (LMw), 48 000 (MMw), and 1 200 000 (HMw)) on bleached chemical fibers. Both kinetics of adsorption and equilibrium adsorption measurements have been conducted, and the adsorption has been measured by polyelectrolyte titration. The results show that the LMw polymer can reach all the charges in the fiber wall whereas the MMw and HMw can only reach the charges on the external surfaces of the fibers. It is also shown that the kinetics of adsorption of the LMw polymer is not at all affected by the presence of a saturated layer of HMw polymer on the surface of the fibers. Finally the results from the investigation show that it is possible to have a full coverage of the external surface of the fibers by a high molecular mass polymer and a full coverage of the internal surface of the fibers with a low molecular mass polymer provided that the high molecular mass polymer is adsorbed before addition of the low molecular mass polymer. This is true if the polymers are adsorbed to the same type of groups on the fibers. A simplistic model for describing ployelectrolyte adsorption in turbulent flow also shows good agreement with measured values for the low molecular mass polyelectrolyte whereas the agreement for the high molecular polyelectrolyte is not as good. For the high molecular mass polyelectrolyte a more sophisticated model is needed.
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| 55. |
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| 56. |
- Wågberg, Lars, et al.
(författare)
-
New equipment for detection of polymer induced flocculation of cellulosic fibres by using image analysis - application to microparticle systems
- 2000
-
Ingår i: Chemical Engineering Journal. - 1385-8947 .- 1873-3212. ; 80:03-jan, s. 51-63
-
Tidskriftsartikel (refereegranskat)abstract
- The present investigation has shown that the use of image analysis can be a very efficient way to study the state of flocculation of cellulosic fibres. By an FFT analysis of the grey-values of the collected images, of the flowing fibres, it was possible to evaluate both a degree of flocculation of the fibres and an average diameter of the formed flocs. Calibration with model flocs correlated very well with earlier published data.Investigations regarding flocculation of unbleached cellulosic fibres caused by a microparticle based retention aid, i.e. a combined addition of a high molecular mass cationic polyacrylamide (C-PAM) and a bentonite clay, and a site blocking polymer (SBP) (a dimethylamine epichlorohydrine condensate) were also conducted. The results from these measurements show that a preadsorption of the SEP to a surface coverage of 50% of the fibres (i.e. of its saturation adsorption) resulted in a higher degree of flocculation upon addition of the C-PAM of the microparticle based flocculant. This is probably due to a more extended conformation of the C-PAM out from the surface of the cellulosic fibers. These results were also in accordance with earlier published theories. A simultaneous addition of SEP and C-PAM in the microparticle system was not as efficient, regarding flocculation, as a pre-adsorption of the SEP. This can be explained by the fact that the way that both the SEP and the C-PAM are adsorbed is affected by the way the polymers are added. In accordance with earlier publishd data the results indicate that the adsorption of SEP is strongly affected by the presence of the C-PAM.The results nevertheless show that an addition of a SEP has a positive effect on microparticle based retention aids.Finally the present results clearly demonstrate that the polymer addition levels in flocculation studies (which are relevant for practical use) are comparably low compared with saturation adsorption on the fibres and the difference in flocculating ability of differently charged C-PAM is small, compared with their corresponding saturation adsorption. Further investigations in this area are strongly recommended.
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| 57. |
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| 58. |
- Wågberg, Lars
(författare)
-
Polyelectrolyte adsorption onto cellulose fibres - A review
- 2000
-
Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 15:5, s. 586-597
-
Tidskriftsartikel (refereegranskat)abstract
- This review focuses upon the following questions: a) Why are the polyelectrolytes adsorbed onto cellulosic fibres? The easiest way to describe the adsorption is as an interaction between the charges on the fibres and the charges on the polyelectrolytes. However the entropy gain upon the release of counterions to the charges on the fibres and the polyelectrolytes gives a much larger contribution to the adsorption energy than the charge interaction. There are some investigations which clarify the influence of certain basic parameters on the fibres and the surfaces and these investigations will be reviewed. An attempt will also be made to create a link between published adsorption data and the Scheutjens-Fleer theory for polyelectrolyte adsorption. Another important question is how the polyelectrolytes are adsorbed on the fibres, i.e. are the segments only found in trains on the surface or will there be some loops and/or tails protruding into the solution? Very little is known about this but the topic will be discussed in some detail. b) Where are the polyelectrolytes adsorbed - on the external surfaces of the fibres or within the fibre wall and how is this related to the molecular properties of the polyelectrolytes? There are a lot of definitions in the literature about fibre surfaces, external surfaces etc. but it is important to link the adsorption to molecular properties and the work in this area will be reviewed. The influence of fines will also be discussed. c) What controls the kinetics of polyelectrolyte adsorption and are there models to describe this adsorption? It is still not entirely known how polymers that adsorb onto the internal surfaces of the fibres are then transported through the fibre wall. The work conducted in this area will be reviewed, It is also important to know the kinetics of the reconformation of the polymer on the fibre surface and this topic will also be discussed in detail. Finally the kinetics of desorption will be treated.
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| 59. |
- Wågberg, Lars
(författare)
-
Polyelectrolyte adsorption onto cellulose fibres - A review
- 2000
-
Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 15:5, s. 586-597
-
Tidskriftsartikel (refereegranskat)abstract
- This review focuses upon the following questions: a) Why are the polyelectrolytes adsorbed onto cellulosic fibres? The easiest way to describe the adsorption is as an interaction between the charges on the fibres and the charges on the polyelectrolytes. However the entropy gain upon the release of counterions to the charges on the fibres and the polyelectrolytes gives a much larger contribution to the adsorption energy than the charge interaction. There are some investigations which clarify the influence of certain basic parameters on the fibres and the surfaces and these investigations will be reviewed. An attempt will also be made to create a link between published adsorption data and the Scheutjens-Fleer theory for polyelectrolyte adsorption. Another important question is how the polyelectrolytes are adsorbed on the fibres, i.e. are the segments only found in trains on the surface or will there be some loops and/or tails protruding into the solution? Very little is known about this but the topic will be discussed in some detail. b) Where are the polyelectrolytes adsorbed - on the external surfaces of the fibres or within the fibre wall and how is this related to the molecular properties of the polyelectrolytes? There are a lot of definitions in the literature about fibre surfaces, external surfaces etc. but it is important to link the adsorption to molecular properties and the work in this area will be reviewed. The influence of fines will also be discussed. c) What controls the kinetics of polyelectrolyte adsorption and are there models to describe this adsorption? It is still not entirely known how polymers that adsorb onto the internal surfaces of the fibres are then transported through the fibre wall. The work conducted in this area will be reviewed, It is also important to know the kinetics of the reconformation of the polymer on the fibre surface and this topic will also be discussed in detail. Finally the kinetics of desorption will be treated.
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| 60. |
- Wågberg, Lars, et al.
(författare)
-
Spreading of droplets of different liquids on specially structured papers
- 2000
-
Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 15:5, s. 598-606
-
Tidskriftsartikel (refereegranskat)abstract
- The spreading kinetics of drops of different liquids (water, glycerol and ethylene glycol) on different types of model papers have been investigated. In the first part of the investigation single ply and two-ply papers, made from pulps with different degrees of beating, were investigated. The results show that is very common the surface layer of the paper had a much larger influence on the spreading than the bottom ply. By normalising the data showing the drop radius as a function of time with the viscosity and surface tension of the liquids all data collapse onto a master curve. The results from the first part of the investigation also show that in order to determine a contact angle between the liquid and the paper the drop volume should remain constant and the contact angle should be determined when the drop has reached its equilibrium volume. In the second part of the investigation the influence of surface topography and surface energy of the papers on the spreading kinetics was determined. The results show that when the pattern of use, the avails on the surface creates fine capillaries the contact angle is decreased compared to the situation with a flat surface. For papers with a higher roughness the uneven structure creates barriers against the spreading which increases the contact angle compared to the situation with a flat surface. A simple attempt to fit the data to a power law based on a hydrodynamic approach was also conducted. The results from this treatment show that it is possible to get a good match for the sheets with virtually only surface spreading. The constants achieved in this treatment can be used to rationalise the spreading data to be compared with other investigations.
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| 61. |
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| 62. |
- Wågberg, Lars, et al.
(författare)
-
Spreading of droplets of different liquids on specially structured papers
- 2000
-
Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 15:5, s. 598-606
-
Tidskriftsartikel (refereegranskat)abstract
- The spreading kinetics of drops of different liquids (water, glycerol and ethylene glycol) on different types of model papers have been investigated. In the first part of the investigation single ply and two-ply papers, made from pulps with different degrees of beating, were investigated. The results show that is very common the surface layer of the paper had a much larger influence on the spreading than the bottom ply. By normalising the data showing the drop radius as a function of time with the viscosity and surface tension of the liquids all data collapse onto a master curve. The results from the first part of the investigation also show that in order to determine a contact angle between the liquid and the paper the drop volume should remain constant and the contact angle should be determined when the drop has reached its equilibrium volume. In the second part of the investigation the influence of surface topography and surface energy of the papers on the spreading kinetics was determined. The results show that when the pattern of use, the avails on the surface creates fine capillaries the contact angle is decreased compared to the situation with a flat surface. For papers with a higher roughness the uneven structure creates barriers against the spreading which increases the contact angle compared to the situation with a flat surface. A simple attempt to fit the data to a power law based on a hydrodynamic approach was also conducted. The results from this treatment show that it is possible to get a good match for the sheets with virtually only surface spreading. The constants achieved in this treatment can be used to rationalise the spreading data to be compared with other investigations.
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| 63. |
- Zhang, Jin, et al.
(författare)
-
The effect of charge density and hydrophobic modification on dextran-based paper strength enhancing polymers
- 2000
-
Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 15:5, s. 440-445
-
Tidskriftsartikel (refereegranskat)abstract
- The dry tensile strengths of bleached kraft pulp handsheets were measured as functions of the cationic charge density and hydrophobic substituents on 2 million Dalton dextran adsorbed onto the fibers before sheet making. The charge density controlled the maximum amount of dextran that could be adsorbed by the fibers which, in turn, influenced tensile strength. The lower the charge density, the higher were both the dextran adsorption capacity of fibers and the tensile strength of the resulting paper. Butanoic and hexanoic acid when condensed onto dextran gave hydrophobic domains which lowered paper strength linearly with hydrophobic content. An extension to the Page equation gave a semi-empirical model which predicted the major effects of hydrophobic substitution on paper strength.
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| 64. |
- Zhang, J., et al.
(författare)
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The effect of molecular weight on the performance of paper strength-enhancing polymers
- 2001
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Ingår i: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 27:5, s. 145-151
-
Tidskriftsartikel (refereegranskat)abstract
- The influence of dextran molecular weight (77 000 to 2 000 000) on the strength of fibre-fibre bonds was investigated. A series of cationic dextrans with different molecular weights, from 77 000 to 2 000 000, was prepared and the adsorption behaviour on fibre was characterized. The maximum amount of adsorbed dextran increased with decreasing molecular weight, while the adsorbed layer thickness on colloidal silica increased with increasing molecular weight. At saturation coverage, the molecular weight of dextran did nor affect the tensile strength of handsheets made from unbeaten bleached kraft pulp. The strength improvement with polymer addition did not correspond to increased optical bonded area (opacity). The external surface of fibre accessible to dextran of molecular weight 2 000 000 was estimated as 35 m(2)/g.
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