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  • 101.
    Carlsson, Peter
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Tinnsten, Mats
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Optimization of acoustic response with numerical and experimental comparison2001In: Proceedings of the Eighth International Congress on Sound and Vibration 2001 : 2-6 July 2001, the Hong Kong Polytechnic University, Hong Kong, China: ICSV8, Hong Kong 2001, Hong Kong: Hong Kong Polytechnic University , 2001, p. 2121-2128Conference paper (Refereed)
  • 102.
    Carlsson, Peter
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Tinnsten, Mats
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Optimization of Drying Schedules Adapted for a Mixture of Bords with Distribution of Sapwood and Heartwood2002In: Drying Technology, ISSN 0737-3937, E-ISSN 1532-2300, Vol. 20, no 2, p. 403-418Article in journal (Refereed)
    Abstract [en]

    A distributed optimization model for wood drying with several different boards simultaneously is presented. Optimization is performed with a gradient-based program. During optimization, convex subproblems are created and transformed to the dual problem and solved. Arbitrary outtakes and board dimensions are possible, as well as different material data and distribution of sapwood and heartwood. It is also possible to optimize drying schedules where drying of boards with variations in environmental conditions is simulated. A two-dimensional orthotropic drying model is used in the moisture transport and structural analysis, where the variation in radial and tangential directions are considered. The influence of temperature and moisture content on material data and mechanical properties is also taken into account. The drying schedules achieved are optimized to minimize drying time for a representative mixture of boards. A numerical example is presented where the drying schedule is optimized for two boards with different outtakes and distributions of sapwood and heartwood. Optimization is performed with two computers in a network. Drying starts from the fibre saturation point in these simulations.

  • 103.
    Carlsson, Peter
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Tinnsten, Mats
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Optimized wood drying of a mixture of representative boards2001In: Moisture control in environment-friendly housing and wood drying technology in new century : July 9-13, 2001 Tsukuba, Japan: 7th International IUFRO Wood Drying Conference proceedings, Ibaraki, Japan: Forestry and Forest Products Research Institute , 2001, p. 461-Conference paper (Refereed)
  • 104.
    Carlsson, Peter
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Tinnsten, Mats
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Stochastic optimization of violin tops2001In: International symposium on musical acoustics 2001. - Perugia, Italia, 10-14 September 2001: ISMA 2001 ; (Perugia) : 2001, Venezia: Fondazione Giorgio Cini , 2001, p. 640-Conference paper (Refereed)
  • 105.
    Carlsson, Peter
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Tinnsten, Mats
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Esping, Björn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Optimization of a racing ski: Brief notes1995In: Structural Optimization, ISSN 0934-4373, Vol. 10, no 1, p. 61-63Article in journal (Refereed)
    Abstract [en]

    This paper shows how very tradition-bound construction can be improved through the use of modern technology. In this case, a cross-country ski, the construction can be traced back to a ski found in a swamp in Vasterbotten in northern Sweden, a ski approximately 5000 years old. (4 refs.)

  • 106.
    Cegrell, Urban
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    A comparison priciple for the complex Monge-Ampere operator2003Book (Other academic)
    Abstract [en]

    A comparison priniple for the complex Monge-Ampere operator

  • 107.
    Cegrell, Urban
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    A general Dirichlet problem for the Complex Monge-Ampere operator2006Report (Other academic)
  • 108.
    Cegrell, Urban
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Approximation of plurisubharmonic functions in hyperconvex domains2006Report (Other academic)
  • 109.
    Cegrell, Urban
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Boundary values of plurisubharmonic functions2004Book (Other academic)
  • 110.
    Cegrell, Urban
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Boundary values of plurisubharmonic functions and a general Dirichlet problem for the complex Monge-Amp`ere operator2005Book (Other academic)
    Abstract [en]

    Boundary values of plurisubharmonic functions and a general Dirichlet problem for the Complex Monge-Amp`ere operator. Research reports, No 1, 2005. Mid Sweden Univ.

  • 111.
    Cegrell, Urban
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Convergence in capacity2001Report (Other academic)
    Abstract [en]

    Convergence in capacity

  • 112.
    Cegrell, Urban
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Potentials with respect to the pluricomplex Green function2006Report (Other academic)
  • 113.
    Cegrell, Urban
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    The general definition of the complex Monge-Ampere operator2004In: Annales de l'Institut Fourier, ISSN 0373-0956, E-ISSN 1777-5310, Vol. 54, no 1, p. 159-179Article in journal (Refereed)
    Abstract [en]

    We define and study the domain of definition for the complex Monge-Ampere operator. This domain is the most general if we require the operator to be continuous under decreasing limits. The domain is given in terms of approximation by certain "test"-plurisubharmonic functions. We prove estimates, study of decomposition theorem for positive measures and solve a Dirichlet problem.

  • 114.
    Cegrell, Urban
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    The gradient lemma2007In: Annales Polonici Mathematici, ISSN 0066-2216, E-ISSN 1730-6272, Vol. 91, no 2-3, p. 143-146Article in journal (Refereed)
    Abstract [en]

    We show that if a decreasing sequence of subharmonic functions converges to a function in W-loc(1,2) then the convergence is in W-loc(1,2) .

  • 115.
    Cegrell, Urban
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Weak*-convergence of Monge-Amp`ere measures2005Book (Other academic)
    Abstract [en]

    Weak*-convergence of Monge-Amp`ere measures. Research reports, No 3, 2005. Mid Sweden Univ.

  • 116.
    Cegrell, Urban
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Weak*-convergence of Monge-Amp`ere measures2006In: Mathematische Zeitschrift, ISSN 0025-5874, Vol. 254, no 3, p. 505-508Article in journal (Refereed)
    Abstract [en]

    We study the convergence of sequences of Monge-Ampère measures (dd c u j ) n where (u j ) is a given sequence of plurisubharmonic functions. Our main theorem is about approximation by multipole pluricomplex Green functions.

  • 117.
    Cegrell, Urban
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Kolodziej, Slawomir
    Zeriahi, Ahmed
    Subextension of plurisubharmonic functions with weak singularities2005In: Mathematische Zeitschrift, ISSN 1432-1823, Vol. 250, no 1, p. 7-22Article in journal (Refereed)
  • 118.
    Cegrell, Urban
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics. Department of Mathematics, Umeå University, Umeå.
    Kołodziej, Slawomir
    Institute of Mathematics, Jagiellonian University, Reymonta 4, 30-059 Kraków, Poland.
    The equation of complex Monge-Amp`ere type and stability of solutions2003In: Mathematische Annalen, ISSN 0025-5831, Vol. 334, no 4, p. 713-729Article in journal (Refereed)
    Abstract [en]

    We prove that in a family of plurisubharmonic functions with Monge-Ampère measures bounded from above by such a measure of one function weak convergence is equivalent to convergence in capacity. We also show a very general statement on the existence of solutions of the complex Monge-Ampère type equation.

  • 119.
    Cegrell, Urban
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Wiklund, J
    A Monge-Ampere norm for Delta-plurisubharmonic functions2004Report (Other academic)
  • 120.
    Cegrell, Urban
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Wiklund, Jonas
    A Monge-Ampere norm for Delta-plurisubharmonic functions2005In: Mathematica Scandinavica, ISSN 0025-5521, Vol. 97, no 2, p. 201-216Article in journal (Refereed)
    Abstract [en]

    We consider differences of plurisubharmonic functions in the energy classF as a linear space, and equip this space with a norm, depending on the generalized complex Monge-Ampère operator, turning the linear space into a Banach space δF. Fundamental topological questions for this space is studied, and we prove that δF is not separable. Moreover we investigate the dual space. The study is concluded with comparison between δF and the space of delta-plurisubharmonic functions, with norm depending on the total variation of the Laplace mass, studied by the first author in an earlier paper

  • 121.
    Cegrell, Urban
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Zeriahi, Ahmed
    Subextension of plurisubharmonic functions with bounded Monge-Ampere mass.2003In: Comptes Rendus Mathématique. Académie des Sciences., ISSN 1631-073X, Vol. 336, no 4, p. 305-308Article in journal (Refereed)
    Abstract [en]

    Subextension of plurisubharmonic functions with bounded Monge-Ampere mass.

  • 122. Cheng, Aijie
    et al.
    Gulliksson, Mårten
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Finite difference methods for saturated-unsaturated flow in porous media2003Report (Other academic)
  • 123. Chunjiang, Y
    et al.
    Tabikl, A
    Leckner, Bo
    Zhang, Wennan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Modeling of deposition and emission of alkalis in boiler systems: Mid-term reporting for project JOR3CT980306 of 4th EU-framework Programme2000Report (Other scientific)
  • 124. Cieslik, D
    et al.
    Dress, A
    Huber, Katharina T
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Moulton, Vincent
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Connectivity calculus2003In: Applied Mathematics Letters, ISSN 0893-9659, E-ISSN 1873-5452, Vol. 16, no 3, p. 395-399Article in journal (Refereed)
    Abstract [en]

    Given a finite hypergraph H = (V, E) and, for each e E E, a collection of nonempty subsets pi(e) of e, Mobius inversion is used to establish a recursive formula for the number of connected components of the hypergraph H = (V, boolean OR(eis an element ofE)pi(e)). As shown elsewhere, this formula is an essential ingredient in the context of a certain divide-and-conquer strategy that allows us to define a dynamical programming scheme solving Steiner's problem for graphs in linear time (however, with a constant depending hyperexponentially on their tree width).

  • 125.
    Coppel, Ludovic
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Lindberg, S
    Rydefalk, S
    Whiteness assessment of paper samples at the vicinity of the upper CIE whiteness limit2007In: 26th Session of the CIE, 2007Conference paper (Refereed)
  • 126.
    Dahlen, Leon
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Carlsson, Peter
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Numerical optimization of a distributor valve2005In: WIT Transaction on the Built Environment, 2005, Vol. 80, p. 333-343Conference paper (Refereed)
  • 127.
    Dahlen, Leon
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Carlsson, Peter
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Kuzmin, Leonid
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Olsson, Nils
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Tinnsten, Mats
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Adventure technology and sport science - A research project at Mid Sweden University: 5th international engineering of sport. 13-16 september, UC Davis, USA.2004Conference paper (Other scientific)
  • 128.
    Dahlén, Leon
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Numerical and experimental study of performance of a hydraulic motor2003Doctoral thesis, monograph (Other academic)
    Abstract [en]

    The aim of this study was to develop an understanding of the fluid properties that influence the efficiency of hydraulic systems in a steady-state, especially components in hydrostatic transmission systems under different running conditions. The aim has also been to investigate and model the sources of losses in hydraulic machines, in order to estimate the losses, taking fluid properties into account. Finally, the technique of optimization has been introduced in order to improve the efficiency of a distributor valve in a radial piston hydraulic motor, Marathon M200. From an experimental field-test, which was performed on a belt conveyer using a hydrostatic transmission system, the overall efficiency of the hydrostatic transmission was compared when using a mineral oil, Shell Tellus TX 68, a synthetic fluid, Mobil SHC 526, and a vegetable fluid, Binol Hydrap II. The experimental field-test showed that vegetable and synthetic fluids improve the efficiency compared to mineral oil. The three fluids have the same viscosity but experimental tests showed that the temperature ()- and pressure() -viscosity coefficient differs between them. It was also found that the pressure-viscosity coefficient () of mineral oil was higher compared to vegetable and synthetic fluids. The proposed steady-state model gives greater accuracy regarding overall efficiency than the Wilson model, when examining fluid properties that differ in other aspects than their viscosity. The study has focused on losses in lubricated sliding contacts within a radial piston hydraulic motor, Marathon M200, and an analysis of the losses has been made using the finite element method (FEM). A FEM software package, Solvia, which takes into account fluid properties, such as temperature- and pressure- viscosity coefficient, heat conduction and specific heat, has been used to simulate the behaviour and to estimate the losses in tribological contact. This approach of simulation has been applied to two different tribological contact within the hydraulic motor: to a journal bearing contact and to a hydrostatic annular multi-recess plane thrust bearing. By using an FEM software package linked to an optimization algorithm, the losses in the tribological contact in a distributor valve were reduced significantly. The study shows that the optimized geometry of the distributor valve in the motor can successfully be improved, with regard to losses, by small changes in the geometry. Combining an FEM software package with the optimization routine offers an effective tool for designers to simulate and improve the efficiency of a hydraulic unit.

  • 129.
    Dahlén, Leon
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Carlsson, Peter
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Numerical optimization of a distributor valve2003In: International Journal of Fluid Power, ISSN 1439-9776, Vol. 4, no 3, p. 17-25Article in journal (Refereed)
    Abstract [en]

    In this paper a non-linear optimization method is used to improve the design of a distributor valve. The distributor valve is an important component in a radial piston hydraulic motor, and optimization of the design to minimize power losses is an interesting way to increase efficiency. The main function of a distributor valve is to supply the pistons with a pressurized flow and to return oil during rotation. At the same time the distributor valve acts as an externally pressurized lubricated thrust bearing, in order to separate the rotating parts from the motor case. The bearing acts as a hydrostatic annular multi-recess plane thrust bearing, with different recess pressures. The separating force of the bearing is balanced hydrostatically by the pressure that is applied and springs. Losses will occur in the contact between the parts in the distributor valve, due to friction and leakage. This paper shows that modern optimization methods can be used as an effective tool to create new designs and to modify the existing design of the bearing surface geometry of the distributor. A finite element method has been used to simulate the contact, and the program is linked to an optimization routine to perform the optimization. The results of the optimized design show a significant decrease in power loss, compared to the existing design in the operating range. (23 refs.)

  • 130.
    Dahlén, Leon
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Isaksson, Ove
    Luleå University of Technology, Division of Machine Elements, Luleå.
    Vegetable and synthetic hydraulic fluids to improve the overall efficiency of a hydrostatic transmission2001In: Journal of Synthetic Lubrication, ISSN 0265-6582, Vol. 17, no 4, p. 263-276Article in journal (Refereed)
    Abstract [en]

    The purpose of the investigation reported here was to determine whether or not a hydrostatic transmission can act as an alternative to a conventional one, and, if so, to ascertain to what extent the fluid type contributes to an improvement in the efficiency of the hydrostatic transmission. The results presented in this paper are derived from an experimental field test of the hydrostatic transmission of a belt conveyor. This belt conveyor is one part in an ore-transport line at LKAB mining company in Kiruna. The hydrostatic transmission replaced a conventional transmission consisting of an electric motor, a belt drive and a gearbox. The hydrostatic transmission was operated using three different hydraulic fluids: Shell Tellus TX 68, a conventional mineral oil; Mobil SHC 526, a synthetic fluid; and Binol Hydrap II, a vegetable fluid. All fluids have the same ISO viscosity grade, VG 68. The measurements on the transmission show a 3% overall efficiency improvement when using vegetable and synthetic hydraulic fluids compared with the mineral oil. The current at the start of the transmission was reduced by a factor of 6, compared to that of the conventional transmission. The installed 110 kW electric motor was replaced with one of 55 kW. The test also showed that a closer study of all operating conditions, and a selection of components suited to the size of the load, can improve the overall efficiency of the hydrostatic transmission.

  • 131.
    Dahlén, Leon
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Olsson, H
    Analysis of Two Sliding Contacts Inside a Radial Piston Hydraulic Motor2002In: Proceedings at 5th JFPS International Symposium on Fluid Power, Nov. 12-15, 2002, Nara, Japan, 2002Conference paper (Other scientific)
    Abstract [en]

    This paper presents an investigation of the torque losses in a hydraulic motor of radial piston type commonly used in industrial hydrostatic transmissions. When the speed of the hydraulic motor is decreased an increase of the torque loss can be measured. In order to investigate the reason for this increase a combination of experimental and theoretical studies is performed with special focus on two sliding contacts-the distributor valve and the piston-cam roller contact. The theoretical analysis of the contacts reveals that the distributor valve contribute more to torque and power losses compared to the piston-cam roller contacts and largely to the external leakage of the motor. At low speeds the piston-cam roller contact will enter the mixed lubrication regime.

  • 132.
    Dahlén, Leon
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Olsson, Håkan
    A study of two lubricated contacts in a radial piston hydraulic motor2003In: The Eighth Scandinavian International Conference on Fluid Power, Proceedings of the conference, Vol 2.: SICFP'03, May 7-9, Tampere, Finland (2003), Tampere: Tampere techn. University , 2003, p. 931-936Conference paper (Other academic)
    Abstract [en]

    The aim of this study is to analyse two sliding contacts in a radial piston hydraulic motor and study their influence on the leakage and power losses. By the use of commercially available FEM software package the losses in the two contacts, the distributor valve and the piston cam-roller contact, are estimated by simulation and related to experimentally measured losses of the motor under different operating conditions. The estimated losses from the two contacts can not explain the total losses and seems also to be a smaller part of the total losses. As long as full film lubrication is present the power losses from the two studied contacts appears to be relatively small. The hydrostatic balancing effect contributes mostly to the external leakage in the piston cam-roller contact. Measured leakage dependency of speed can be related to the piston cam-roller contacts in the motor. At low speed and high load the piston cam-roller contact might enter mix lubrication regime.

  • 133. Derevianko, A
    et al.
    Hemmers, O
    Oblad, S
    Glans, Peter
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Wang, H
    Whitfield, S.B.
    Wehlitz, R
    Sellin, I.A.
    Johnson, W.R.
    Lindle, D.W.
    Electric-octupole and pure-electric-quadrupole effects in soft-X-ray photoemission2000In: Physical Review Letters, ISSN 0031-9007, Vol. 84, no 10, p. 2116-2119Article in journal (Refereed)
    Abstract [en]

    Second-order [O(k(2)), k = omega/c] nondipole effects in soft-x-ray photoemission are demonstrated via an experimental and a theoretical study of angular distributions of neon valence photoelectrons in the 100-1200 eV photon-energy range. A newly derived theoretical expression for nondipolar angular distributions characterizes the second-order effects using four new parameters with primary contributions from pure-quadrupole and octupole-dipole interference terms;Independent-particle calculations of these parameters account for a significant portion of the existing discrepancy between experiment and theory for Ne 2p first-order nondipole parameters.

  • 134.
    Dieu, Nguyen Quang
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Local hulls of unions of totally real graphs lying in real analytic hypersurfaces2000In: The Michigan mathematical journal, ISSN 0026-2285, E-ISSN 1945-2365, Vol. 47, no 2, p. 335-351Article in journal (Refereed)
  • 135. Dieu, Nguyen Quang
    et al.
    Wikström, Frank
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Jensen measures and approximation of plurisubharmonic functions2005In: Michigan Mathematical Journal, ISSN 0026-2285, Vol. 53, no 3, p. 529-544Article in journal (Refereed)
    Abstract [en]

    Let $Omega$ be a bounded domain in $Cn$. We study relations between Jensen measures for continuous and upper bounded plurisubharmonic functions on $Omega$, and give some conditions on $Omega$ that imply that these two classes of measures coincide.

  • 136. Do-Quang, Minah
    et al.
    Amberg, G
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Three-dimensional Modeling of Radial Segregation due to Weak Convection2004In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 269, no 2-4, p. 454-463Article in journal (Refereed)
    Abstract [en]

    A comprehensive three-dimensional, time-dependent model of heat, momentum and solute transfer during solidification is carried out to illustrate the influence of weak convection, caused by surface tension forces, on radial dopant segregation occurring in crystal growth under micro-gravity conditions. 3D adaptive finite element method is used in order to simulate the motion and deformation of the solidification interface. The geometry studied is a Bridgman configuration with a partly coated surface. The small slots in the coating gives a free surface in a controlled way, and is varied in order to alter the Marangom flow. in this study, A comparison is made between the numerical results and the experimental results. A good agreement has been observed for the effective distribution coefficient k(eff) and for the radial segregation Deltac'. The radial dopant segregation is affected by weak convection.

     

  • 137.
    Dornburg, Veronika
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Estimating GHG emission mitigation supply curves of large-scale biomass use on a country level2007In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 31, no 1, p. 46-65Article in journal (Refereed)
    Abstract [en]

    This study evaluates the possible influences of a large-scale introduction of biomass material and energy systems and their market volumes on land, material and energy market prices and their feedback to greenhouse gas (GHG) emission mitigation costs. GHG emission mitigation supply curves for large-scale biomass use were compiled using a methodology that combines a bottom-up analysis of biomass applications, biomass cost supply curves and market prices of land, biornaterials and bioenergy carriers. These market prices depend on the scale of biomass use and the market volume of materials and energy carriers and were estimated using own-price elasticities of demand. The methodology was demonstrated for a case study of Poland in the year 2015 applying different scenarios on economic development and trade in Europe. For the key technologies considered, i.e. medium density fibreboard, poly lactic acid, electricity and methanol production, GHG emission mitigation costs increase strongly with the scale of biomass production. Large-scale introduction of biomass use decreases the GHG emission reduction potential at costs below 50EURO/Mg CO2eq with about 13-70% depending on the scenario. Biomaterial production accounts for only a small part of this GHG emission reduction potential due to relatively small material markets and the subsequent strong decrease of biomaterial market prices at large scale of production. GHG emission mitigation costs depend strongly on biomass supply curves, own-price elasticity of land and market volumes of bioenergy carriers. The analysis shows that these influences should be taken into account for developing biomass implementations strategies.

  • 138.
    Dornburg, Veronika
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Optimising waste treatment systems - Part A: Methodology and technological data for optimising energy production and economic performance2006In: Resources, Conservation and Recycling, ISSN 0921-3449, E-ISSN 1879-0658, Vol. 49, no 1, p. 68-88Article in journal (Refereed)
    Abstract [en]

    The treatment and utilisation of biomass residues and waste for energy and recycling can contribute significantly to greenhouse gas emission reduction. Therefore, a waste treatment structure should be designed for an efficient saving of fossil primary energy in terms of maximal primary energy savings or minimal costs per unit of primary energy savings. However, this is a complex task, given the large number of technologies, recycling options and their logistic consequences, that necessitate an integrated analysis. Also, on longer term various new and improved technologies become available which can affect performances for options from an economic and/or energy point of view. For that reason, an optimisation tool, that optimises a biomass and waste treatment system for a given amount of biomass and waste, is developed in this study. This optimal biomass and waste treatment system is composed of several treatment installations, that are characterised by scale, location and kind of technology. Important aspects that are taken into account in the analysis are heat distribution, biomass and waste transport and economies of scale. A broad variety of technologies for material recycling, conversion of biomass and/or waste to heat, electricity or transportation fuel are included in the optimisation tool. Performance data of these technologies are based on an extensive review. Examples of included technologies comprise: integrated gasification with combined cycle, waste incineration, pyrolysis, digestion, co-firing in fossil power plants, biomass incineration, hydro-thermal upgrading, paper recycling and chipboard production. A comparison of the different technologies in relation to scale shows that primary energy savings and costs per unit of primary energy savings diverge significantly. In general, the optimisation tool developed here is suitable for analyses of optimal biomass and waste treatment structures in different regions with regard to primary energy savings and their costs. By means of scenario analysis, robust optimal solutions in terms of primary energy savings and their costs can be identified and the influence of important parameters can be analysed. A case study of the Dutch biomass and waste treatment systems has been carried out with the optimisation tool and is presented in part two of this article.

  • 139.
    Dornburg, Veronika
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Eggers, Thies
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Gustavsson, Leif
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Integrated carbon analysis of biomass production on fallow agricultural land and product substitution in Sweden - preliminary results2006Conference paper (Refereed)
    Abstract [en]

    An important option in the Swedish context to reduce its net emissions of carbon dioxide (CO2) is the increased use of biomass for energy and material substitution. On fallow agricultural land additional production of biomass would be possible. We analyse biomass production systems based on Norway spruce, hybrid poplar and willow hybrids and the use of this biomass to replace fossil energy and energy intensive material systems. The highest biomass production potential is for willow in southern Sweden. Fertilisation management of spruce could shorten the rotation lengths by about 17%. The fertilised production of Norway spruce with use of harvested timber for construction and use of remaining woody biomass for heat and power production gives the largest reductions of carbon emissions per hectare under the assumptions made. The use of willow for heat and power and of fertilised spruce for a wood product mix lead to the highest fossil primary energy savings in our scenarios. Spruce cultivations can achieve considerable carbon emission reductions in the long term, but willow and poplar might be a good option when fossil energy savings and carbon emission reductions should be achieved in the short term.

  • 140.
    Dornburg, Veronika
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Faaij, APC
    Optimising waste treatment systems - Part B: Analyses and scenarios for The Netherlands2006In: Resources, Conservation and Recycling, ISSN 0921-3449, E-ISSN 1879-0658, Vol. 48, no 3, p. 227-248Article in journal (Refereed)
    Abstract [en]

    Material recycling as well as energetic production of biomass residues and other solid wastes could significantly contribute to fossil primary energy savings. Waste treatment should, therefore, aim to combine pollution abatement with the efficient saving of fossil primary energy. This article identifies optimal waste treatment strategies in The Netherlands. Here, an optimal strategy is one that either maximises the fossil primary energy savings or minimises the costs per unit of fossil primary energy savings that are achieved by the utilisation of available biomass residues and wastes. Also, the influence of different factors - for example, the availability of wastes or technological developments - on the robustness of technological options and on the variation of costs and fossil primary energy savings is studied. With a specially developed optimisation tool (described in Part I of this article series) several variants of Dutch waste treatment systems ('scenarios') are analysed by back casting to the year 2020. This tool allows for quick analyses of complete waste treatment infrastructures. The results show that the objective of the Dutch government to supply 120PJ of primary energy demand in 2020 from biomass and waste seems more than feasible, while in 2000 about 43 PJ were realised. Including material recycling up to 437 PJ primary energy could be saved with an optimised waste treatment infrastructure. Choices made about alternative waste treatment strategies influence the costs strongly. Total costs for the Dutch waste treatment system - not considering revenues from waste treatment tariffs - vary from revenues of 230EUEO million/year to costs of 820EURO million/year. The contributions of material and energy recycling to avoid primary energy use change significantly under different preconditions. In the 11 different scenarios considered, of the primary energy savings achieved 25-76% resulted from material recycling, 20-80% from heat and electricity production, and a more modest 0-21% from the production of transport fuel. (Biomass) integrated gasification with combined cycle, hydro-thermal upgrading and waste separation emerge as key technologies from this study, while for example, waste incineration and biomass co-firing in coal power plants do not come out as most attractive options for the longer term. Generally, large-scale conversion units seem favourable to achieve better economies and energy recovery.

  • 141. Dress, A.
    et al.
    Huber, K. T.
    Moulton, Vincent
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Affine maps that induce polyhedral complex isomorphisms2000In: Discrete & Computational Geometry, ISSN 0179-5376, E-ISSN 1432-0444, Vol. 24, no 1, p. 49-60Article in journal (Refereed)
    Abstract [en]

    In this paper we show that an affine bijection f: T-1 --> T-2 between two polyhedral complexes T-1, T-2, both of which consist of a union of faces of two convex polyhedra P-1 and P-2, necessarily respects the cell-complex structure of T-1 and T-2 inherited from P-1 and P-2, respectively, provided f extends to an affine map from P-1 into P-2. In addition, we present an application of this result within the area of T-theory to obtain a far-reaching generalization of previous results regarding the equivalence of two distinct constructions of the phylogenetic tree associated to "perfect" (that is, treelike) distance data.

  • 142. Dress, A.
    et al.
    Huber, K. T.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Moulton, Vincent
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    An explicit computation of the injective hull of certain finite metric spaces in terms of their associated Buneman complex2002In: Advances in Mathematics, ISSN 0001-8708, E-ISSN 1090-2082, Vol. 168, no 1, p. 1-28Article in journal (Refereed)
  • 143. Dress, A.
    et al.
    Huber, K. T.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Moulton, Vincent
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Antipodal metrics and split systems2002In: European journal of combinatorics (Print), ISSN 0195-6698, E-ISSN 1095-9971, Vol. 23, no 2, p. 187-200Article in journal (Refereed)
    Abstract [en]

    Recall that a metric d on a finite set X is called antipodal if there exists a map sigma : X --> X: x --> (x) over bar so that d(x, (x) over bar) = d(x, y) + d(y, (x) over bar) holds for all x, y epsilon X. Antipodal metrics canonically arise as metrics induced on specific weighted graphs, although their abundance becomes clearer in light of the fact that any finite metric space can be isometrically embedded in a more or less canonical way into an antipodal metric space called its full antipodal extension. In this paper, we examine in some detail antipodal metrics that are, in addition, totally split decomposable. In particular, we give an explicit characterization of such metrics, and prove that-somewhat surprisingly-the full antipodal extension of a proper metric d on a finite set X is totally split decomposable if and only if d is linear or #X = 3 holds.

  • 144.
    Dress, A.
    et al.
    FSPM-Strukturbildungsprozesse, University of Bielefeld, D-33501 Bielefeld, Germany.
    Huber, Katharina T
    Institute of Fundamental Sciences, Massey University, Private Bag 11 222, Palmerston North, New Zealand.
    Koolen, J. H.
    FSPM-Strukturbildungsprozesse, University of Bielefeld, D-33501 Bielefeld, Germany.
    Moulton, Vincent
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Six points suffice: How to check for metric consistency2001In: European journal of combinatorics (Print), ISSN 0195-6698, E-ISSN 1095-9971, Vol. 22, no 4, p. 465-474Article in journal (Refereed)
    Abstract [en]

    In many areas of data analysis, it is desirable to have tools at hand for analyzing the structure of distance tables-or, in more mathematical terms, of finite metric spaces. One such tool, known as split decomposition theory has proven particularly useful in this respect. Tbe class of so-called totally decomposable metrics forms a cornerstone for this theory, and much work has been devoted to their study. Recently, it has become apparent that a particular subclass of these metrics, the consistent metrics, are also of fundamental importance. In this paper, we give a six-point characterization of consistent metrics amongst the totally decomposable ones.

  • 145. Dress, A.
    et al.
    Koolen, J. H.
    Moulton, Vincent
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    On line arrangements in the hyperbolic plane2002In: European journal of combinatorics (Print), ISSN 0195-6698, E-ISSN 1095-9971, Vol. 23, no 5, p. 549-557Article in journal (Refereed)
    Abstract [en]

    Given a finite collection L of lines in the hyperbolic plane H, we denote by k = k(L) its Karzanov number, i.e., the maximal number of pairwise intersecting lines in L, and by C(L) and n = n(L) the set and the number, respectively, of those points at infinity that are incident with at least one line from L. By using purely combinatorial properties of cyclic seta:, it is shown that #L less than or equal to 2nk - ((2k+1)(2)) always holds and that #L equals 2nk - ((2k+1)(2)) if and only if there is no collection L' of lines in H with L subset of or equal to L', k(L') = k(L) and C(L') = C(L).

  • 146. Edenhagen, Görgen
    et al.
    Bäckström, Ingela
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Schön, Lennart
    Wiklund, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Improving continuing engineering education through institutional co-operation: a swedish case study2004In: Proceedings of the 9th World Conference on Continuing Engineering Education – Tokyo May 15–20, 2004: 9th IACEE World Conference on Continuing Engineering Education, 2004, p. 195-200Conference paper (Refereed)
    Abstract [en]

    This paper presents a unique CEE-collaboration between three universities in Sweden concerning the development of a distance course in quality technology and management. The course is based on distance spanning technology and is mainly aimed at engineers who have a degree and have been working for a few years. The background, organisation and practical experiences from the co-operative course development work are presented and discussed in the paper

  • 147.
    Edström, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    A Comparison Between the Coefficients of the Kubelka-Munk and DORT2002 Models2003Report (Other academic)
    Abstract [en]

    This paper gives the exact translation and between the scattering and absorption coefficients of the Kubelka-Munk and DORT2002 models. It is shown that the conditions, under which this exact translation is valid, are perfectly diffuse light, perfectly isotropic scattering, and only two channels in the DORT2002 model. Reasons for non-validity in other cases are given. It is also shown that it is possible to use grammage instead of thickness for DORT2002, as has previously been shown for Kubelka-Munk. Since the s and k values of the Kubelka-Munk model are so well known and in such widespread use, a translation to and from the DORT2002 coefficients will make it easy to use the models together, to compare results, and to change from one model to the other.

  • 148.
    Edström, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    A Fast and Stable Solution Method for the Radiative Transfer Problem2005In: SIAM Review, ISSN 0036-1445, E-ISSN 1095-7200, Vol. 47, no 3, p. 447-468Article in journal (Refereed)
    Abstract [en]

    Radiative transfer theory considers radiation in turbid media, and is used in a wide range of applications. This paper outlines a problem formulation and a solution method for the radiative transfer problem in multilayer scattering and absorbing media, using discrete ordinate model geometry. A selection of different steps is brought together. The main contribution here is the synthesis of these steps, all of which have been used in different areas, but never all together in one method. First all necessary steps to get a numerically stable solution procedure are treated, and then methods are introduced to increase the speed by a factor of several thousand. This includes methods for handling strongly forward-scattering media. The method is shown to be unconditionally stable, whilst the problem was previously considered numerically intractable.

  • 149.
    Edström, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Comparison of the DORT2002 Radiative Transfer Solution Method and the Kubelka-Munk Model2004In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 19, no 3, p. 397-403Article in journal (Refereed)
    Abstract [en]

    The need for optical modeling of paper is obvious to provide connections between its optical response and the actual properties of the paper. It is argued that modern solution methods from radiative transfer theory could be considered instead of the Kubelka-Munk model, and a specific example, DORT2002, is tested. It is shown that Kubelka-Munk is a simple special case of DORT2002, and the two models and their coefficients are compared. A comprehensive list of advantages for the applied user of a model with higher dimensionality is supplied. It is shown, by the use of DORT2002, that when the medium has finite thickness, the light distribution deviates from the perfectly diffuse even under the theoretically ideal conditions for which Kubelka-Munk was created. This effect causes errors in Kubelka-Munk reflectance calculations that may be up to 20% and more, even for a grammage of 80 g/m2. The magnitude of the error shows a strong dependence on the degree of light absorption, with higher absorption giving greater error. DORT2002 can well be considered for increased understanding in cases where the level of accuracy of Kubelka-Munk reflectance calculations is not sufficient.

  • 150.
    Edström, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Efficient Reflectance Calculations and Parameter Estimation Methods for Radiative Transfer Problems in Paper Industry Applications2007Report (Other academic)
    Abstract [en]

    Very fast code for standardized d/0° reflectance calculations and an efficient Gauss-Newton parameter estimation method are introduced into the radiative transfer based light scattering simulation tool DORT2002, which makes it competitive in paper industry applications. Outstanding problems in general radiative transfer theory are addressed in a paper industry application. The parameter estimation problem is given a least-squares formulation, different solution methods are evaluated, some characteristics of the problem are found, and the sensitivity of the solution is analyzed. Tests show that Gauss-Newton type methods are most suitable for the studied parameter estimation problem; superior performance was shown with respect to both robustness and speed. The parameter estimation problem is shown to be non-trivial and sometimes ill-conditioned. The type of analyses made in this work give good insight in the character of the problem, and similar studies will be valuable in the future design of measurements and parameter estimation methods when using angle-resolved measurements to estimate also the asymmetry factor.

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