| 1. |
- Lavrykov, S., et al.
(författare)
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3D network simulations of paper structure
- 2012
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Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 27:2, s. 256-263
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Tidskriftsartikel (refereegranskat)abstract
- The structure of paper influences its properties and simulations of it are necessary to understand the impact of fiber and papermaking conditions on the sheet properties. We show a method to develop a representative structure of paper by merging different simulation techniques for the forming section and the pressing operation. The simulation follows the bending and drape of fibers over one another in the final structure and allows estimation of sheet properties without recourse to arbitrary bending rules or experimental measurements of density and/or RBA. Fibers are first modeled as jointed beams following the fluid mechanics in the forming section. The sheet structure obtained from this is representative of the wet sheet from the couch. The pressing simulation discretizes fibers into a number of solid elements around the lumen. Bonding between fibers is simulated using spring elements. The resulting fiber network was analyzed to determine its elastic modulus and deformation under small strains. The influence of fiber dimensions, namely fiber lengths, widths and thicknesses as well as bond stiffnesses on the elasticity of the network are studied. A brief account of inclusion of fines, represented by individual cubical elements is also shown.
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| 2. |
- Lavrykov, Sergiy, et al.
(författare)
-
3D network simulations of paper structurewith fines and fillers
- 2012
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Ingår i: Nordic Pulp and Paper Research Journal. - 0283-2631. ; 27:2, s. 256-263
-
Tidskriftsartikel (refereegranskat)abstract
- The structure of paper influences its properties and simulations of it are necessary to understand the impact of fiber and papermaking conditions on the sheet properties. We show a method to develop a representative structure of paper by merging different simulation techniques for the forming section and the pressing operation. The simulation follows the bending and drape of fibers over one another in the final structure and allows estimation of sheet properties without recourse to arbitrary bending rules or experimental measurements of density and/or RBA. Fibers are first modeled as jointed beams following the fluid mechanics in the forming section. The sheet structure obtained from this is representative of the wet sheet from the couch. The pressing simulation discretizes fibers into a number of solid elements around the lumen. Bonding between fibers is simulated using spring elements. The resulting fiber network was analyzed to determine its elastic modulus and deformation under small strains. The influence of fiber dimensions, namely fiber lengths, widths and thicknesses as well as bond stiffnesses on the elasticity of the network are studied. A brief account of inclusion of fines, represented by individual cubical elements is also shown.
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| 3. |
- Lindström, Stefan B, et al.
(författare)
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Forming of paper sheets : A numerical simulation based on hydrodynamics of fibrous suspensions
- 2012
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Ingår i: Proc. of PaperCon 2012. - : TAPPI. ; , s. 1221-1279
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A fiber-level simulation of paper forming in a twin-wire roll former is conducted with a furnish typical of fine paper. A mix of bleached kraft softwood and hardwood pulps was chosen, each refined to different levels. The resultant web structure obtained from the couch roll was determined from these numerical experiments. This wet web structure is used as input to a simulation of wet pressing, which produces a consolidated sheet structure. Results regarding how the change in fiber mix (e.g. HW/SW ratio) and changes in pulp refining affect the structure of the web are shown. Important features such as sheet fiber orientations, anisotropy, retention of fibers, fines and fillers and sheet exit moisture are all predicted by the simulation.
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| 4. |
- Ravindran, A., et al.
(författare)
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A differential CMOS current-mode variable gain amplifier with digital dB-linear gain control
- 2004
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Ingår i: Analog Integrated Circuits and Signal Processing. - 0925-1030 .- 1573-1979. ; 38:03-feb, s. 161-174
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Tidskriftsartikel (refereegranskat)abstract
- A novel CMOS variable gain amplifier operating on current signals with a dB-linear gain control is presented. The gain control is achieved by multiplying a digitally synthesized exponentially varying control current signal by a differential input signal in the current domain. A current amplifier at the output sets the gain to the desired level. Current-mode operation allows for a reduced supply voltage by minimizing the voltage swing at the low impedance nodes of the circuit. Multiple circuit realizations for various blocks are presented allowing for designs meeting different constraints. Experimental realization of the variable gain amplifier shows the validity of the presented approach.
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| 5. |
- Ravindran, A., et al.
(författare)
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Compact low voltage four quadrant CMOS current multiplier
- 2001
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Ingår i: Electronics Letters. - : Institution of Engineering and Technology (IET). - 0013-5194 .- 1350-911X. ; 37:24, s. 1428-1429
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Tidskriftsartikel (refereegranskat)abstract
- A new compact low voltage four quadrant current mode CMOS multiplier is presented. Post layout simulation in a CMOS 0.5 mum technology shows a linearity error lower than 0.9% for signal swings up to +/- 50 muA. The Circuit operates at a supply of +/- 1.5V, has a static power dissipation of 0.6 mW and a 1 dB bandwidth of 33 MHz.
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