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  • 151.
    Edström, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Examination of the Revised Kubelka-Munk Theory: Considerations of Modeling Strategies2007Ingår i: Journal of the Optical Society of America A, ISSN 0740-3232, Vol. 24, nr 2, s. 548-556Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The revised Kubelka-Munk theory is examined theoretically and experimentally. Systems of dyed paper sheets are simulated, and the results are compared with other models. The results show that the revised Kubelka-Munk model yields significant errors in predicted dye-paper mixture reflectances, and is not self-consistent. The absorption is noticeably overestimated. Theoretical arguments show that properties in the revised Kubelka-Munk theory are inadequately derived. The main conclusion is that the revised Kubelka-Munk theory is wrong in the inclusion of the so-called scattering-induced-path-variation factor. Consequently, the theory should not be used for light scattering calculations. Instead, the original Kubelka-Munk theory should be used where its accuracy is sufficient, and a radiative transfer tool of higher resolution should be used where higher accuracy is needed.

  • 152.
    Edström, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Fast and Stable Solution Method for Angle-Resolved Light Scattering Simulation2002Rapport (Övrigt vetenskapligt)
    Abstract [en]

    This report extensively treats a problem formulation of and a solution method to the radiative transfer problem, including some adaptations to the area of light scattering in paper and print. The resulting model is referred to as DORT2002, and has been implemented in MATLAB using a discrete ordinate model geometry. The main steps to get a numerically stable solution procedure include the continuous formulation with expansion in Legendre functions and Fourier cosine series, the evaluation of normalized associated Legendre functions, the choice of numerical quadrature, the matrix formulation of the discretization, the reduction of the eigenvalue problem, the preconditioning of the system of equations for the boundary conditions, and the avoidance of over- and underflow in the solution and interpolation formulas. Important are also the recognition of potential divide-by-zero situations, and reformulation of those. Comments are given on possible applications in the paper and printing industries. It is suggested that the Kubelka-Munk model should be replaced with DORT2002 in most applications.

  • 153.
    Edström, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Fast and Stable Solution Method for Angle-Resolved Light Scattering Simulation III: Handling Refractive Index Discontinuities2005Rapport (Övrigt vetenskapligt)
    Abstract [en]

    The change in refractive index that occurs at the interface between air and an ink-paper substrate causes effects such as refraction and total reflection. This report uses radiative transfer theory to account for these effects exactly, and for any measurement geometry, without approximations and without unknown constants. This is in contrast with Kubelka-Munk and the Saunderson correction, which is only an approximation and only for integrating sphere geometry, and which requires non-trivial determination of unknown constants. This report continues previous work, and extends the solution procedure of DORT2002 to handle a discontinuous change in refractive index at the interface between two perfectly flat layers. The result of a large number of consistency and accuracy tests are presented, and they are all positive. Some comments on planned and suggested future work are given regarding direct and inverse model development, but also for comparative studies. Comments are also given on the benefit of this work for the paper and printing industries. It is suggested that the Kubelka-Munk model should be replaced with DORT2002 in most applications.

  • 154.
    Edström, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Inverse Scattering: athematical Modelling in a Changing World, Berlin2001Konferensbidrag (Övrigt vetenskapligt)
  • 155.
    Edström, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Ljus idé kastar nytt ljus på ljusspridning i papper och tryck: Ekmandagarna, Stockholm2007Konferensbidrag (Övrigt vetenskapligt)
  • 156.
    Edström, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Mathematical modeling and numerical tools for simulation and design of light scattering in paper and print2007Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    This work starts with a real industrial problem - the perceived need for a moredetailed and more accurate model for light scattering in paper and print than theKubelka‐Munk model of today. A careful analysis transfers this problem into aphysical description of the phenomena involved. This is then given a mathematicalformulation, and a detailed analysis leads to numerical solution procedures forspecific sub problems. Methods from scientific computing make it possible to meetindustrial demands made on speed and stability, and implementation in computercode is then followed by analysis of accuracy and stability.A problem formulation and a solution method are outlined for the forwardradiative transfer problem. First, all necessary steps to arrive at a numericallystable solution procedure are treated, and then methods are introduced to increasethe speed by a factor of several thousands or millions compared to a naiveapproach. The method is shown to be unconditionally stable, though the problemwas previously considered numerically intractable, and systematic studies ofnumerical performance are presented.The inverse radiative transfer problem is given a least‐squares formulation, anddifferent solution methods are analyzed and compared. Specifically, a two‐phasemethod for estimation of the scattering and absorption coefficients and theasymmetry factor (σs, σa and g) is presented. A sensitivity analysis is given, and it isshown how it can be used for designing measurements with minimal impact frommeasurement noise.It is shown how the standardized use of Kubelka‐Munk and the d/0°instrument leads to errors, and that the errors arising from an over‐idealized viewof the instrument - due to the fact that instrument readings are incorrectlyinterpreted - can be larger than any errors inherent in the Kubelka‐Munk modelitself. It is argued that the measurement device and the simulation model cannot beviewed as separate instances, which is a widespread implicit practice in appliedreflectance measurements. Rather, given a measurement device, measurement datashould be interpreted through a model that takes into consideration the actualgeometry, function and calibration of the instrument.The resulting tool, DORT2002, is in all aspects the Next Generation Kubelka‐Munk, and provides a greater range of applicability, higher accuracy and increasedunderstanding. It offers better interpretation of measurement data, and facilitatesthe exchange of data between the paper and graphical arts industries. It opens forunderstanding of anisotropic reflectance and for the utilization of the asymmetryfactor to design anisotropy, and thereby for the design of different visualappearance or optical performance in new printed or paper products.

  • 157.
    Edström, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Mathematical Modelling of Light Scattering in Paper and Print2004Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    A problem formulation and a solution method are outlined for the radiative transfer problem in vertically inhomogeneous scattering and absorbing media, using discrete ordinate model geometry. The treatment spans from the physical problem via a continuous formulation, a discretization and a numerical analysis, to an implementation with performance evaluation and application to real-world problems. The thesis clearly illustrates how considerations in one step affect other steps, and thus provides an example of an overall treatment of mathematical modeling of a large applied problem. A selection of different steps is brought together. First all the steps necessary to get a numerically stable solution procedure are treated, and then methods are introduced to increase the speed by a factor of several thousand. The solution procedure is implemented in MATLAB under the name of DORT2002, and is adapted primarily to light scattering simulations in paper and print. A confined presentation is given of the effect of the steps that are needed, or possible, to make any discrete ordinate radiative transfer solution method numerically efficient. This is done through studies of the numerical performance of DORT2002. Performance tests show that the steps that are included to improve stability and speed of DORT2002 are very successful. Together they give an unconditionally stable solution method to a problem previously considered numerically intractable, and decrease computation time compared to a naive implementation with a factor of 1 000 � 10 000 in typical cases and with a factor up to and beyond 10 000 000 in extreme cases. It is also shown that the speed increasing steps are not introduced at the cost of reduced accuracy, and that DORT2002 converges to the true value as the discretization is made finer. It is shown by the use of DORT2002 that when a medium has a finite thickness, the light distribution deviates from the perfectly diffuse even under the theoretically ideal conditions for which the Kubelka-Munk model was created. This effect, which is in opposition to what one would intuitively expect, is caused by light escaping through the lower boundary of the medium, and causes errors in Kubelka-Munk reflectance calculations that can 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 absorption, with higher absorption giving greater error. This confirms previously reported problems with Kubelka-Munk for strongly absorbing media, and DORT2002 offers a partial explanation of these problems, as it can describe this effect and quantify the Kubelka-Munk errors. It is argued that DORT2002 could well be considered for increased understanding in cases where the level of accuracy of Kubelka-Munk reflectance calculations is not acceptable. A comprehensive list of advantages for the applied user of a model with higher dimensionality is supplied.

  • 158.
    Edström, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Modeller och metoder för ljusspridning i papper: Ekmandagarna, Stockholm2002Konferensbidrag (Övrigt vetenskapligt)
  • 159.
    Edström, Per
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Granberg, H
    Gulliksson, Mårten
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Some Ideas on Models and Methods for Light Scattering in Paper2001Rapport (Övrigt vetenskapligt)
    Abstract [en]

    In this report a short overview is given on existing models for simulating light scattering in paper. The well known Kubelka-Munk model somewhat oversimplifies the problem. Newer discrete ordinate models take into account more aspects, e.g. angle resolved scattering, but have intrinsic ill-conditioned problems that have to be overcome. No existing models are designed to solve the inverse problem, i.e. finding model parameters given real light scattering measurements. Therefore we propose a Stable Multilayer Discrete Ordinate Radiative Transfer model, SM-DORT, to simulate the scattering of light in coated paper and similar structures, and to solve the corresponding inverse problem. We discuss improvements of existing models, for making SM-DORT stable to give reliable results in spite of intrinsic ill-conditioned problems, and for making it fast to efficiently solve the inverse problem. In this report we also cover some aspects of inverse problems in general, we give some ideas on further model improvement to take into account more aspects of light scattering in paper, and we discuss model validation, using experiments and existing models.

  • 160.
    Edström, Per
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Lehto, Marcus
    DORT2002 version 2.0 User Manual2003Rapport (Övrigt vetenskapligt)
    Abstract [en]

    The DORT2002 software is a fast and accurate tool for solving radiative transfer problems in vertically inhomogeneous turbid media, using a discrete ordinate model geometry. DORT2002 is implemented in MATLAB, and is adapted to light scattering simulations in paper and print. The DORT2002 Graphical User Interface is a tool developed to provide users with a fast and easy way of performing DORT2002 simulations. It works as a shell that encapsulates the parameters and the function calls, and offers powerful simulations through a mouse click. This report gives a thorough description of how to install and use DORT2002, version 2.0, and the Graphical User Interface.

  • 161.
    Edström, Per
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Lehto, Marcus
    Fast and Stable Solution Method for Angle-Resolved Light Scattering Simulation II - Model Enhancements2003Rapport (Övrigt vetenskapligt)
    Abstract [en]

    This report continues previous work to extensively treat a solution method to the radiative transfer problem. Several enhancements have been made, including handling of multilayer structures, handling of sharply peaked phase functions, and code optimization. The resulting model is referred to as DORT2002, now in version 2.0, and has been implemented in MATLAB using a discrete ordinate model geometry. The introduction of a graphical user interface makes the model easy to use, and any desired simulation is just a button-click away. The main steps to get a numerically stable multilayer solution procedure include the preconditioning of the system of equations for the boundary and continuity conditions, and the avoidance of over- and underflow in the multilayer solution and interpolation formulas. Important are also the recognition of potential divide-by-zero situations, and reformulation of those. Several measures are taken to make the code fast. This includes exploitation of the sparse structure of the system of equations for the boundary and continuity conditions. Several features allow high speed by maintaining accuracy at significantly lower number of channels than would otherwise be needed, or by automatically stopping calculations earlier when certain convergence criteria have been met. Comments are given on possible applications in the paper and printing industries. It is suggested that the Kubelka-Munk model should be replaced with DORT2002 in most applications.

  • 162.
    Edström, Per
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Lehto, Marcus
    Performance and application of the DORT2002 light scattering simulation model2003Rapport (Övrigt vetenskapligt)
    Abstract [en]

    Models for calculating the light intensity inside an illuminated turbid medium, e.g. paper, involve several numerical challenges, and are crucial for the paper and printing industries. DORT2002 is a fast and numerically stable solution procedure for this problem, which has been implemented in MATLAB. This report studies the performance and application of DORT2002, and is the documentation of an extensive test series. All major steps that are taken to improve stability and speed of DORT2002 are discussed, and the resulting improvements are illustrated. Comparison of accuracy, applicability and speed between DORT2002 and three other models when applied to different sets of relevant test problems is covered. The performance tests show that the steps that are taken to improve stability and speed of DORT2002 are very successful, together giving an unconditionally stable solution procedure to a problem previously considered numerically intractable, and together decreasing computation time with a factor 1 000-10 000 in typical cases and with a factor up to and beyond 10 000 000 in extreme cases. Further investigations and developments are suggested, that can have a large positive impact on computation time. The application tests show very good agreement with three other model types. DORT2002 is shown to have better accuracy and much larger range of applicability than Kubelka-Munk, and to be much faster than Grace in relevant test cases. It is also shown that DORT2002 and Grace have good agreement, and that the agreement between the results from DORT2002 and DISORT  which is claimed to be the finest radiative transfer software available - is very good without exception, which gives strong support for the accuracy of DORT2002. The conclusion is that Kubelka-Munk should be replaced with DORT2002 for most applications, and that a combination of Grace and DORT2002 should be used for accurate modeling of paper and print.

  • 163.
    Eggers, Thies
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Dornburg, Veronika
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Gustavsson, Leif
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Integrated carbon analysis of biomass production on fallow agricultural land and biomass utilisation2007Konferensbidrag (Refereegranskat)
    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 in southern Sweden with use of harvested timber for material or construction gives the largest reductions of carbon emissions per hectare in the long term. The use of willow and poplar for heat and power and of fertilised spruce for construction lead to the highest fossil primary energy savings in southern and central Sweden. Short-rotation willow and poplar are a good option when fossil energy savings and carbon emission reductions should be achieved in the short term.

  • 164.
    Ekdahl, F.
    et al.
    ABB Corporate Research.
    Persson, P.
    Linköping University.
    Sandvik Wiklund, Pia
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Introducing domain knowledge for selection of active factors in designed experiments2000Ingår i: International Journal of Reliability, Quality and Safety Engineering (IJRQSE), ISSN 0218-5393, Vol. 7, nr 4, s. 341-356Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Unreplicated factorial designs are widely used for designed experimentation in industry. In the analysis of designed experiments, the experimental factors influencing the response must be identified and separated from those that do not. An abundance of procedures intended to perform this selection have been introduced in the literature. A recent study indicated that the procedure due to Box and Meyer outperforms the lot of the other selection procedures in terms of efficiency and robustness. The procedure of Box and Meyer rests on a quasi-Bayesian foundation and utilizes generic domain knowledge, in the form of a common-for-all-factors a priori probability, that a factor significantly influences the response, to calculate an a posteriori probability for each factor. This paper suggests a strategy for introducing more elaborate domain knowledge about the experimental factors in the procedure of Box and Meyer, aiming to further improve its performance.

  • 165.
    Ekenberg, Love
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Thorbiornson, Johan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Second-order decision analysis2001Ingår i: International Journal of Uncertainty Fuzziness and Knowledge-Based Systems, ISSN 0218-4885, Vol. 9, nr 1, s. 13-37Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The purpose of this work is to provide theoretical foundations of, as well as some computational aspects on, a theory for analysing decisions under risk, when the available information is vague and imprecise. Many approaches to model unprecise information, e.g., by using interval methods, have prevailed. However, such representation models are unnecessarily restrictive since they do not admit discrimination between beliefs in different values, i.e., the epistemologically possible values have equal weights. In many situations, for instance, when the underlying information results from learning techniques based on variance analyses of statistical data, the expressibility must be extended for a more perceptive treatment of the decision situation. Our contribution herein is an approach for enabling a refinement of the representation model, allowing for an elaborated discrimination of possible values by using belief distributions with weak restrictions. We show how to derive admissible classes of local distributions from sets of global distributions and introduce measures expressing into which extent explicit local distributions can be used for modelling decision situations. As will turn out, this results in a theory that has very attractive features from a computational viewpoint.

  • 166.
    Ekenberg, Love
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Thorbiornson, Johan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Baidya, Tara
    Value Differences using Second Order Distributions2005Ingår i: International Journal of Approximate Reasoning, ISSN 0888-613X, Vol. 38, nr 1, s. 81-97Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Most decision models for handling vague and imprecise information are unnecessarily restrictive since they do not admit for discrimination between different beliefs in different values. This is true for classical utility theory as well as for the various interval methods that have prevailed. To allow for more refined estimates, we suggest a framework designed for evaluating decision situations considering beliefs in sets of epistemically possible utility and probability functions, as well as relations between them. The various beliefs are expressed using different kinds of belief distributions. We show that the use of such distributions allows for representation principles not requiring too hard data aggregation, but still admitting efficient evaluation of decision situations.

  • 167.
    Ekholm, Tobias
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Kutzschebauch, Frank
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Total curvature and area of curves with cusps and of surface maps2003Rapport (Övrigt vetenskapligt)
  • 168.
    Ekholm, Tobias
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Kutzschebauch, Frank
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Total curvature and area of curves with cusps and of surface maps.2005Ingår i: Mathematica Scandinavica, ISSN 0025-5521, E-ISSN 1903-1807, Vol. 96, nr 2, s. 224-242Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A curvature-area inequality for planar curves with cusps is derived. Using this inequality, the total (Lipschitz-Killing) curvature of a map with stable singularities of a closed surface into the plane is shown to be bounded below by the area of the map divided by the square of the radius of the smallest ball containing the image of the map. This latter result fills the gap in Santalo's [7] proof of a similar estimate for surface maps into R-n, n > 2.

  • 169. Eklöw, N
    et al.
    Glans, Peter
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Zong, W
    Schuch, R
    Danared, H
    Magnetic-field dependence in electron-deuteron recombination at very low relative energy2000Ingår i: Hyperfine Interactions, ISSN 0304-3843, E-ISSN 1572-9540, Vol. 127, nr 1-4, s. 251-255Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The rate coefficient for recombination of D+ with low-energy electrons has been measured at different magnetic fields in the interaction region of the electron cooler at CRYRING. It is found that the measured recombination rate coefficient is influenced by the magnetic field.

  • 170.
    Ekvall, Jenny
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Control of the Drying Section in a Paper Machine During a Web Break: Reglermöte 2004, Göteborg2004Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    A new control strategy for steam pressure control in the drying cylinders during web breaks is presented. The development is performed using a new physical model implemented in Matlab Simulink. The goal of the control strategy is to obtain the same drying properties after the web break as before the break as fast as possible.

  • 171.
    Ekvall, Jenny
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Dryer section control in paper machines during web2006Ingår i: 13th Nordic Process Control Workshop Köpenhamn 2006, 2006Konferensbidrag (Övrigt vetenskapligt)
  • 172.
    Ekvall, Jenny
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Dryer Section Control in Paper Machines During Web Breaks2004Licentiatavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    Web breaks in the dryer section of a paper machine cause loss of production and quality problems. After a web break, the steam pressure in the cylinders must be reduced to avoid overheating. The goal of this project is to determine optimal steam pressure trajectories during web breaks, so that the production is restarted with the same drying properties of the cylinder as before the break. A detailed physical dynamic model of the drying cylinder has been developed. The model describes the relations between the steam valve position, the steam pressure, the cylinder temperature, and the paper temperature. The model is based on partial differential equations that describe heat conductivity for the cylinder and the paper web, and mass balances of water and dry material in the paper. The accuracy of the model has been verified through experiments made at the M-real paper mill in Husum, Sweden. Verifications are made both during normal operation and during web breaks. The dynamic model has been reduced in order to derive simple transfer functions between the steam pressure and the cylinder temperature, and between a logic signal that is active during web breaks and the cylinder temperature, respectively. The transfer functions obtained were used to find the optimal steam pressure trajectory during web breaks. A new feed-forward strategy for steam pressure control during web breaks is presented. The strategy has been tested on a paper machine with good results. The strategy is built on feed-forward compensation and has been well received at the mill.

  • 173.
    Ekvall, Jenny
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Steam Pressure Control During Web Breaks in the Paper Machine: Control Systems 2004, Quebec City, Canada2004Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    A new control strategy for steam pressure control in the drying cylinders during web breaks is presented. The development is performed using a new physical model implemented in Simulink. The goal of the control strategy is that the cylinder temperatures are retained when the production is restarted after the web break.

  • 174. Elstad, Olav
    et al.
    Widing, Angelica
    Bonde, Henrik
    Bring, Gunnar
    Edvinsson, Josefin
    Rosenquist, Jakob
    Englund, Andreas
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Miljöbelastningsbedömning av vissa energi- och materiaflöden vid Mitthögskolan1998Rapport (Övrigt vetenskapligt)
  • 175.
    Englund, Andreas
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Miljöbelastningsbedömning av byggnadsprodukter: beskrivning av Landscape-metoden1999Rapport (Övrig (populärvetenskap, debatt, mm))
  • 176.
    Englund, Andreas
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Mosten, Peter
    Miljöbelastningsbedömning av byggnadsprodukter - beskrivning av Landscape-metoden: reviderat utkast1999Rapport (Övrigt vetenskapligt)
  • 177.
    Engström, Clas
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Pauler, Nils
    Wågberg, Jerker
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Edström, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Final Report on the Project: Optical Interaction between Ink and Paper2007Rapport (Övrigt vetenskapligt)
  • 178. Eriksson, Erik
    et al.
    Gillespie, Andrew
    Gustavsson, Leif
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Langvall, Ola
    Olsson, Mats
    Sathre, Roger
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Stendahl, Johan
    Integrated carbon analysis of forest management practices and wood substitution2007Ingår i: Canadian Journal of Forest Research, ISSN 0045-5067, E-ISSN 1208-6037, Vol. 37, nr 3, s. 671-681Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The complex fluxes between standing and harvested carbon stocks, and the linkage between harvested biomassand fossil fuel substitution, call for a holistic, system-wide analysis in a life-cycle perspective to evaluate the impacts offorest management and forest product use on carbon balances. We have analysed the net carbon emission under alternativeforest management strategies and product uses, considering the carbon fluxes and stocks associated with tree biomass,soils, and forest products. Simulations were made using three Norway spruce (Picea abies (L.) Karst.) forest managementregimes (traditional, intensive management, and intensive fertilization), three slash management practices (no removal, removal,and removal with stumps), two forest product uses (construction material and biofuel), and two reference fossilfuels (coal and natural gas). The greatest reduction of net carbon emission occurred when the forest was fertilized, slashand stumps were harvested, wood was used as construction material, and the reference fossil fuel was coal. The lowest reductionoccurred with a traditional forest management, forest residues retained on site, and harvested biomass was used asbiofuel to replace natural gas. Product use had the greatest impact on net carbon emission, whereas forest management regime,reference fossil fuel, and forest residue usage as biofuel were less significant.

  • 179. Eriksson, H
    et al.
    Johanson, F
    Wiklund, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Effects of in-company quality awards on operational performance2002Ingår i: The 7. World congress for total quality management : business excellence, make it happen] : Proceedings, Verona, Italy, 25-27 June 2002: 2 b., Verona: Sinergie-CUEIM , 2002, , s. -Konferensbidrag (Refereegranskat)
  • 180. Eriksson, Henrik
    et al.
    Johansson, Fredrik
    Wiklund, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Effects of In-Company Quality Awards on Organizational Performance2003Ingår i: Total quality management (Print), ISSN 0954-4127, E-ISSN 1360-0613, Vol. 14, nr 2, s. 235-242Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The relationship between total quality management (TQM) practices and improved performance has been frequently discussed in the literature. In this paper, the costs and the effects of in-company quality awards on performance are discussed and analysed. The paper covers a survey of Swedish companies that use or have used in-company quality awards to stimulate TQM efforts and thereby to improve performance. The study cannot show any strong evidence of improved performance for units that applied for the in-company quality award. However, in contrast to units that have not applied, some units that have applied for the in-company quality award considered that the results related to performance have improved greatly. One large positive effect perceived by the participating units was increased customer orientation while the largest costs were put on the description of activities and the improvement work itself.

  • 181.
    Eriksson, Ingela
    et al.
    Umeå universitet.
    Åström, Maria
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Resultat och erfarenheter av de nationella kursproven B, C, D och E2002Ingår i: Dokumentation av 12:e matematikbiennalen: [Norrköping 24-26 januari 2002] : matematik i tiden, Linköping: Universitet , 2002, s. 543-Konferensbidrag (Övrigt vetenskapligt)
  • 182. Eriksson, J
    et al.
    Wedin, P.A.
    Gulliksson, Mårten
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Söderkvist, I
    Regularization methods for uniformly rank-deficient nonlinear least-squares problems2005Ingår i: Journal of Optimization Theory and Applications, ISSN 0022-3239, E-ISSN 1573-2878, Vol. 127, nr 1, s. 1-26Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In solving the nonlinear least-squares problem of minimizing ||f(x)||22, difficulties arise with standard approaches, such as the Levenberg-Marquardt approach, when the Jacobian of f is rank-deficient or very ill-conditioned at the solution. To handle this difficulty, we study a special class of least-squares problems that are uniformly rank-deficient, i.e., the Jacobian of f has the same deficient rank in the neighborhood of a solution. For such problems, the solution is not locally unique. We present two solution tecniques: (i) finding a minimum-norm solution to the basic problem, (ii) using a Tikhonov regularization. Optimality conditions and algorithms are given for both of these strategies. Asymptotical convergence properties of the algorithms are derived and confirmed by numerical experiments. Extensions of the presented ideas make it possible to solve more general nonlinear least-squares problems in which the Jacobian of f at the solution is rank-deficient or ill-conditioned.

  • 183. Eriksson, Jerry
    et al.
    Gulliksson, Mårten E.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Local results for the Gauss-Newton method on constrained rank-deficient nonlinear least squares2004Ingår i: Mathematics of Computation, ISSN 0025-5718, E-ISSN 1088-6842, Vol. 73, nr 248, s. 1865-1883Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A nonlinear least squares problem with nonlinear constraints may be ill posed or even rank-deficient in two ways. Considering the problem formulated as $min_{x} 1/2Vert f_{2}(x) Vert _{2}^{2}$subject to the constraints $f_{1}(x) = 0$, the Jacobian $J_{1} = partial f_{1}/ partial x$ and/or the Jacobian $J = partial f/ partial x$, $f = [f_{1};f_{2}]$, may be ill conditioned at the solution. We analyze the important special case when $J_{1}$ and/or $J$ do not have full rank at the solution. In order to solve such a problem, we formulate a nonlinear least norm problem. Next we describe a truncated Gauss-Newton method. We show that the local convergence rate is determined by the maximum of three independent Rayleigh quotients related to three different spaces in $mathbb{R} ^{n}$. Another way of solving an ill-posed nonlinear least squares problem is to regularize the problem with some parameter that is reduced as the iterates converge to the minimum. Our approach is a Tikhonov based local linear regularization that converges to a minimum norm problem. This approach may be used both for almost and rank-deficient Jacobians. Finally we present computational tests on constructed problems verifying the local analysis.

  • 184.
    Eriksson, Maria
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Ingelsson, Pernilla
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Lilja, Johan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Achieving shared values: Learning from Disney2007Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    The need to achieve a strong corporate culture is one of the key questions within Total Quality Management (TQM). TQM is generally considered to be based on a number of core values; such as customer focus, decisions based on facts, process orientation, continuous improvement, everybody’s commitment and leadership, (Hellsten & Klefsjö, 2000). The core values should ideally be conformed to by all employees within a TQM organization, (ibid). Achieving these core values seems to be rewarding. Many companies that have succeeded in adapting their core values have received quality awards, e.g. Malcolm Baldridge National Quality Award and EFQM Excellence Model. These quality awards are based on values that are widely considered to be the building blocks of effective TQM implementation (Hendricks & Singhal, 1999). There are a lot of descriptions in literature about the importance of working with the ideas of TQM such as putting focus on the customer, establishing processes and also about educating the employees in using tools of improvement, but very little focus on discussing how shared values really are achieved.   A common set of values within an organization is often referred to as the company or corporate culture. A strong culture implies that there is uniformity among the employees regarding, for example values (Pinder 1998). In our literature studies we came across two interesting strategies that combined together provide a tactic for working with shared values to attain a strong corporate culture. According to Chatman (1989) the best way is an integration of the strategies of selection and socialization. That implies both considering values at the selection when the organization chooses its members, by recruiting an individual with the right values and later on by maintaining or reinforcing values by socialization which can be done by training, orientation and other methods. As regards working with achieving TQM values we mostly encountered the use of socialization and feel that there is a need for broader thinking by putting greater emphasis on the selection process when recruiting new members into the organization.   The purpose of this paper is to raise the discussion about how to achieve homogeneity of values, such as TQM values in order to be a successful organization. The presented theories are accompanied by an observation from the renowned Walt Disney World in Florida, providing an example of how they are working with the selection strategy.

  • 185. Erts, D.
    et al.
    Olin, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Holmes, J.D.
    Metallic and Semiconducting Nanowires: Properties and Architectures2003Ingår i: Proceedings of the SPIE - The International Society for Optical Engineering, ISSN 0277-786X, Vol. 5123, s. 256-266Artikel i tidskrift (Refereegranskat)
  • 186.
    Esping, Björn
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Design optimization as an engineering tool1994Rapport (Övrigt vetenskapligt)
  • 187.
    Esping, Björn
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Homogeniserat trä: 2000-talets miljövänliga, höghållfasta konstruktionsmaterial1995Rapport (Övrigt vetenskapligt)
  • 188.
    Esping, Björn
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Optimization of the wood drying process1995Rapport (Övrigt vetenskapligt)
  • 189.
    Esping, Björn
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Clarin, P
    Romell, O
    Octopus: a tool for distributed optimization of multi-disciplinary objectives1994Rapport (Övrigt vetenskapligt)
  • 190.
    Esping, Björn
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Grenestedt, Joachim L
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Composites optimization using lamination parameters in an engineering environment1995Rapport (Övrigt vetenskapligt)
  • 191.
    Esping, Björn
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Tinnsten, Mats
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Carlsson, Peter
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Johnsson, M
    Optimization of violin tops with focus on determining correct material properties2005Ingår i: World Congress on Structural and Multidisciplinary Optimization, 6th. Proceedings (CD-ROM): WCSMO6, May 30 - June 3, Rio de Janeiro, Brazil., 2005Konferensbidrag (Refereegranskat)
  • 192.
    Esping, Björn
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Tinnsten, Mats
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Jonsson, M
    Optimization of acoustic response1995Rapport (Övrigt vetenskapligt)
  • 193.
    Feng, Tao
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Adaptive finite element methods for parameter estimation problems in partial differential equations2005Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Physical and chemical phenomena are often described by a system of partial di®erential equations. These equations usually involve unknown parameters, which cannot be measured directly but which can be adjusted to make the model predictions match the observed data. The process of ¯tting these para- meters to laboratory or plant data is called parameter estimation. In order to recover these parameters, the well-known output least squares formulation is of- ten utilized. To solve the optimization problem governed by partial di®erential equations, the in¯nite-dimensional problem must be approximated by introduc- ing discretizations such as a ¯nite elements or di®erences. It is clear that the e±ciency of the numerical methods dealt with here will be in°uenced by the discretization scheme. The goal of this thesis is to develop e±cient numerical methods for the parameter estimation problems governed by partial di®erential equations, based on adaptive ¯nite element methods. This work was initiated by an investigation into an a posteriori error esti- mator of residual type for parameter estimation problems with a ¯nite number of unknown parameters. It appears that an adaptive ¯nite element algorithm guided by the derived a posteriori error estimator produces a sequence of eco- nomical, locally re¯ned meshes. The methods are then applied to the identi¯ca- tion of elastic constants in paper from measured displacements. Further, some a posteriori error estimators of gradient recovery type are derived for the error in parameters due to the discretization. The main advantages of using error estimators of this type are the simplicity of their implementation and their cost e®ectiveness. Often, the unknown parameters are functions, which also need to be dis- cretized. Adaptive ¯nite element method is developed for the estimation of distributed parameters in elliptic equations with multi-mesh techniques. Finally, a goal-oriented adaptive method, dual weighted residual methods (DWR methods) are employed determining the elastic constants in paper from measured displacements.

  • 194.
    Feng, Tao
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Mixed Finite Elements Methods with Finite Difference Streamline-Diffusion Method for Miscible Displacement in Porous Media2002Ingår i: Journal of Shandong University. Natural Science. Shandong Daxue Xuebao. Lixue Ban, ISSN 1671-9352, Vol. 37, nr 5, s. 391-395Artikel i tidskrift (Refereegranskat)
  • 195.
    Feng, Tao
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Edström, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Gulliksson, Mårten
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Levenberg-Marquardt Methods for Parameter Estimation Problems in the Radiative Transfer Equation2007Ingår i: Inverse Problems, ISSN 0266-5611, E-ISSN 1361-6420, Vol. 23, nr 3, s. 879-891, artikel-id 002Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A discrete ordinate method is developed for solving the radiative transfer equation, and the corresponding parameter estimation problem is given a least-squares formulation. Two Levenberg-Marquardt methods, a feasible-path approach and an SQP type method, are analyzed and compared. A sensitivity analysis is given, and it is shown how it can be used for designing measurements with minimal impact of measurement noise. Numerical experiments are performed to exemplify the usefulness of the theory.

  • 196.
    Feng, Tao
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Gulliksson, Mårten
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Liu, W
    A Posteriori Error Estimators of Recovery Type for Parameter Estimation Problem in Linear Elastic Problem2007Ingår i: Free and Moving Boundaries: Analysis, Simulation and Control, Boca Raton: CRC Press, 2007, s. 395-410Kapitel i bok, del av antologi (Övrigt vetenskapligt)
  • 197.
    Feng, Tao
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Gulliksson, Mårten
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Liu, W
    Institute of Mathematics and Statistics, University of Kent, Canterbury, CT2 7NF, United Kingdom.
    Adaptive finite element methods for the identification of elastic constants2006Ingår i: Journal of Scientific Computing, ISSN 0885-7474, E-ISSN 1573-7691, Vol. 26, nr 2, s. 217-235Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, the elastic constants of a material are recovered from measured displacements where the model is the equilibrium equations for the orthotropic case. The finite element method is used for the discretization of the state equation and the Gauss–Newton method is used to solve the nonlinear least squares problem attained from the parameter estimation problem. A posteriori error estimators are derived and used to improve the accuracy by an appropriate mesh refinement. A numerical experiment is presented to show the applicability of the approach.

  • 198.
    Flodén, Liselott
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    G-convergence and homogenization for some monotone operators with multiple scales2005Licentiatavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    This thesis deals with questions concerning the convergence of sequences of functions and operators. G-convergence is studied for elliptic and parabolic equations and the necessary investigations of the properties of certain monotone operators are made. In particular, we consider periodic cases with oscillations in one or several scales including the possibility of rapid oscillations in time. Homogenization procedures for these problems are developed and local problems are identified.

  • 199.
    Flodén, Liselott
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Holmbom, Anders
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Olsson, Marianne
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Silfver, Jeanette
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    A model for the heat transfer between steel edge and running base in alpine racing skis2006Ingår i: WSEAS transactions on heat and mass transfer.,ISSN 1790-5044, 2006, Vol. 1, nr 3, s. 256-261s. 256-261Konferensbidrag (Refereegranskat)
  • 200.
    Flodén, Liselott
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Holmbom, Anders
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Olsson, Marianne
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Silfver, Jeanette
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    On the convergence and determination of limits for some sequences of differential operators: Presented at The Ninth International Conference on Integral Methods in Science and Engineering, Niagara Falls, Ontario, Canada, July 23-27 20062006Konferensbidrag (Övrigt vetenskapligt)
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