| 51. |
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| 52. |
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| 53. |
- Karlström, Anders, 1958, et al.
(författare)
-
Modelling of wood-chip refining processes
- 1993
-
Ingår i: Nordic Pulp and Paper Research Journal. - 2000-0669 .- 0283-2631. ; 8:4, s. 384-388
-
Tidskriftsartikel (refereegranskat)abstract
- At present, due to the complexity of the wood chip refining processes, there are no suitable physical or parametric models available which can be used when studying different control strategies. It is shown that the process, which consists of two serially linked refiners, can be modelled as two multiple input, single output systems. To each refiner the dynamics from the chip flow to the motor load and from dilution water to the motor load are examined. It is shown that the pressure cannot be ignored in the model and that the motor load of the first refiner can be used as an input when modelling the second refiner. This indicates the possibility to use the load for feed forward control. The time stability of the models found was examined. The survey showed a small change in the model characteristics, but the ability to simulate the motor toads was not significantly reduced.
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| 54. |
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| 55. |
- Karlström, Anders, 1958, et al.
(författare)
-
On the modeling of tensile index from larger data sets
- 2019
-
Ingår i: Nordic Pulp & Paper Research Journal. - : De Gruyter Open Ltd. - 0283-2631 .- 2000-0669. ; 34:3, s. 289-303
-
Tidskriftsartikel (refereegranskat)abstract
- The objective of this study is to analyze and foresee potential outliers in pulp and handsheet properties for larger data sets. The method is divided into two parts comprising a generalized Extreme Studentized Deviate (ESD) procedure for laboratory data followed by an analysis of the findings using a multivariable model based on internal variables (i. e. process variables like consistency and fiber residence time inside the refiner) as predictors. The process data used in this has been obtained from CD-82 refiners and from a laboratory test program perspective, the test series were extensive. In the procedure more than 290 samples were analyzed to get a stable outlier detection. Note, this set was obtained from pulp at one specific operating condition. When comparing such "secured data sets" with process data it is shown that an extended procedure must be performed to get data sets which cover different operating points. Here 100 pulp samples at different process conditions were analyzed. It is shown that only about 60 percent of all tensile index measurements were accepted in the procedure which indicates the need to oversample when performing extensive trials to get reliable pulp and handsheet properties in TMP and CTMP processes.
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| 56. |
- Karlström, Anders, 1958, et al.
(författare)
-
Pulp property development Part I: Interlacing under-sampled pulp properties and TMP process data using piece-wise linear functions
- 2015
-
Ingår i: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 2000-0669 .- 0283-2631. ; 30:4, s. 599-608
-
Tidskriftsartikel (refereegranskat)abstract
- Thermo-Mechanical Pulp (TMP) refiners served in this work as an example of how to combine oversampled and undersampled variables on a common timeframe for further analysis. To get more information from the refining process, temperature measurement arrays in the refining zones were studied alongside process measurements such as motor load, production rates, plate gaps, dilution waters, pulp properties and manually measured blow-line consistency. The undersampled data set consisted of 63 laboratory samples obtained at a Swedish TMP mill, which were tested for tensile index, mean fiber length and Somerville shives content. The pulp samples were obtained at five different periods during three months to cover a large dynamic operating window. The data set was expanded using a piece-wise linear approach. The measurements inside the refining zone were shown to be important variables when interlacing the undersampled pulp properties with the oversampled process data set, consisting of 350 000 samples. Use of an extended entropy model provided a palette of information about the process conditions inside the refining zone. Particularly, the residence time and the consistency in the refining zones were essential for the pulp property development, as a link between the refining segment pattern used and the current state of refiner operation.
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| 57. |
- Karlström, Anders, 1958, et al.
(författare)
-
Pulp property development Part II: Process non-linearities and their influence on pulp property development
- 2016
-
Ingår i: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 2000-0669 .- 0283-2631. ; 31:2, s. 287-
-
Tidskriftsartikel (refereegranskat)abstract
- It is shown in this paper that knowledge of the spatially measured temperatures inside the refining zone in TMP refiners is essential in describing non-linear dynamics of high consistency refining. By expanding the pulp and handsheet properties using piece-wise linear functions into the time domain, an auto-regressive model can be applied to verify that the tempera-ture and the consistency profiles, in combination with the motor load and production rate, are key input candidates when modeling changes in different pulp properties. The model accuracy is analyzed using process information captured at different time and operating conditions. It is also shown that it is more complex to estimate and validate the tensile index than the mean fiber length and Somerville shives content, especially close to refiner operating limits where a shift in the process gain may occur. This type of switched dynamics in tensile index estimation at a specific consistency is related to non-linear behaviors where the fiber pad distribution most likely undergoes a local collapse.
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| 58. |
- Karlström, Anders, 1958, et al.
(författare)
-
Pulp property development Part III: Fiber residence time and consistency profile impact on specific energy and pulp properties
- 2016
-
Ingår i: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 2000-0669 .- 0283-2631. ; 31:2, s. 300-307
-
Tidskriftsartikel (refereegranskat)abstract
- This paper focuses on the pulp properties obtained from ThermoMechanical Pulp (TMP) CD refiners. Undersampled pulp variables are expanded into an oversampled set of process data, which makes it possible to analyze pulp properties in a dynamic time frame. It is shown that, in order to gain deeper insight into the defibration/fibrillation at a specific energy input, one needs to know the fiber residence time and the consistency profile. Moreover, the fiber residence time in the flat zone (FZ) and conical zone (CD) are intertwined with the consistency out from FZ and CD. Together with an external variable (production), these internal variables are essential for predicting the pulp properties. It is also shown that internal process conditions from different test series can be manipulated in the operating window using a low-frequency gain description obtained from an ARX model. The same mapping procedure can be applied to pulp and handsheet properties (in this paper represented by the tensile index), and this opens for implementation of new optimization routines to find more energy efficient operating points while maintaining pre-specified pulp quality.
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| 59. |
- Karlström, Anders, 1958, et al.
(författare)
-
Refiner optimization and control Part I: Fiber residence time and major dynamic fluctuations in TMP refining processes
- 2014
-
Ingår i: Nordic Pulp and Paper Research Journal. - 2000-0669 .- 0283-2631. ; 29:4, s. 635-652
-
Tidskriftsartikel (refereegranskat)abstract
- The study focuses on dynamic considerations in a mill-wide perspective showing that mill economy is closely linked to optimization of TMP and power plant. Special attention is given to stability issues in the refining processes. Describing the dynamics in such nonlinear processes is difficult and tedious and requires significant knowledge about where in the operating window to run the refiners. Results show the dynamics in the internal states, temperature profiles and the plate gap sensors responses and how they correspond to the refiner motor load. Disturbances in production affect the plate gap sensors and the temperature profiles in the same direction, while deliberate changes in the plate gap result in a dynamic situation where the motor load and temperature profile change in opposite directions. It is shown that the total residence time and the ratio between the residence time before and after the maximum temperature will be important when formulating specifications for energy efficient refining. As an example of how the refining process affects the mill economy, the start-up procedures for two different types of refiners will be penetrated. It is shown that the start-ups are most often associated with an over shoot in the motor load, which is easy to overcome.
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| 60. |
- Karlström, Anders, 1958, et al.
(författare)
-
Refiner optimization and control Part II: Test procedures for describing dynamics in TMP refining processes
- 2014
-
Ingår i: Nordic Pulp and Paper Research Journal. - 2000-0669 .- 0283-2631. ; 29:4, s. 653-662
-
Tidskriftsartikel (refereegranskat)abstract
- The present study used a system identification ARMAX modeling approach to analyze how the pulp properties can be predicted from the traditional input variables such as hydraulic pressures and dilution water feed rates at stable production. As a complement internal states from the refining zones are used as inputs in a commercial production line comprising two serially linked Twin refiners. It is shown that neither the hydraulic pressures and dilution water feed rates nor the motor loads from primary and secondary refiners are sufficient as inputs to the ARMAX model to describe the dynamics in the pulp properties. Instead, the temperature profile measurements from the refining zones outperform these traditional inputs and capture the major dynamics in the pulp property studied. It is also shown that the process should be controlled in a way that reduces as much variations inside the refining zones as possible. It is not only necessary to include the maximum temperatures in the refining zones as internal states when estimating pulp properties but also the periphery temperature since temperature profiles are affected differently depending on whether the changes are made in the hydraulic pressure, production or the dilution water feed rates. From a control perspective, refining zone temperature control is preferable to any concepts based on specific energy for minimization of pulp quality variations.
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| 61. |
- Karlström, Anders, 1958, et al.
(författare)
-
Refiner optimization and control Part III: Natural decoupling in TMP refining processes
- 2015
-
Ingår i: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 2000-0669 .- 0283-2631. ; 30:3, s. 417-425
-
Tidskriftsartikel (refereegranskat)abstract
- In TMP-refining processes, the stabilization of the fiber pad inside the refining zone requires a new control approach. Specific energy control tends to be complex and most often affected by a number of disturbances not so well specified in traditional MPC-concepts. To describe the dynamics in such nonlinear processes is difficult, tedious and requires significant maintenance support. This paper focuses on two important issues related to modeling in mechanical pulping processes: measurements of internal states inside the refining zone and in particular natural decoupling to find a model suitable for future process optimization and improved control concepts of complete refiner lines. The idea is to show how this complex process, with serially linked refiners or refining zones, can be modeled and controlled using a simplified process description. In this series of papers, data from a commercial Twin-refiner and a CD-refiner are available as inputs. As an example of internal state measurements, refining zone temperature profiles and estimated distributed consistency in the refining zone are used. We show that the characteristics of the temperature profile dynamics makes it possible to introduce a decoupling scheme where the anti-diagonal elements in the transfer function matrix describing the process can be eliminated naturally, independent of which refiner is to be controlled.
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| 62. |
- Karlström, Anders, 1958, et al.
(författare)
-
Refiner optimization and control Part IV: Long term follow up of control performance in TMP processes
- 2015
-
Ingår i: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 2000-0669 .- 0283-2631. ; 30:3, s. 426-435
-
Tidskriftsartikel (refereegranskat)abstract
- This paper focuses on three important issues; Process understanding in relation to control of nonlinear processes; Natural decoupling by using internal state measurement devices; Long term follow up procedures of process control investments. As an example, a new control system for Thermo Mechanical Pulp (TMP) refiners is used, based on a cascaded control structure. The internal states, in this case the refining zone temperature profiles, are controlled in the inner loop whereas the outer loop handles pulp properties. The characteristics of the temperature profile dynamics makes it possible to introduce a decoupling scheme where the anti-diagonal elements in the transfer function matrix describing the process, can be eliminated naturally. The system can handle several pulp propertied simultaneously but in this study mean fiber length (MFL) is the target variable. The process is followed about 200 days in manual mode control and 200 days in automatic mode. It is shown that the standard deviations in the pulp property variables freeness (CSF) and MFL were decreased about 40 and 60%, respectively. Significant reductions in variability of shives and a motor load standard deviations was achieved. On top of this, an increased production was obtained and the control system runnability was raised from 50% to 98%, levels that are far from commercial MPC-control concepts in TMP refining control.
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| 63. |
- Karlström, Anders, 1958, et al.
(författare)
-
Refining Efficiency for Future CTMP and TMP systems Co-optimizing Fundamental Wood Material Knowledge with a Soft Sensor Control Approach
- 2016
-
Ingår i: International Mechanical Pulp conference. - : TAPPI Press. - 9781510830738 ; , s. 304-316
-
Konferensbidrag (refereegranskat)abstract
- Internal variables in (C)TMP-refining processes (e.g. temperature, consistency, fiber residence time, backward flowing steam and forces acting upon the chips and pulp) are defined as physical states obtained in different parts of the refining zones. In short, they differ from the traditional external variables (e.g. dilution water feed rate, load and gap distance) which are not available as distributed variables from refining zone measurements. The internal variables are the backbone of physical models and such models can be used for on-line implementation of soft sensors and advanced process control. Of special interest are the temperature and consistency profiles together with fiber residence time, which are the internal variables in focus of (in) this study. Moreover, they are directly linked to pulp and handsheet property development. To illustrate the capability to use a modeling strategy, two examples are given; one where it is shown how to reach a 40% reduction in specific energy in a CD82-refiner using a new control strategy without violating the pulp properties studied and one example where the consistency can be controlled individually in two parallel Twin refining zones. Hence, the article comprises both temperature and consistency control to reach optimal process conditions. We believe that increased fundamental understanding of the role of the spatially dependent viscosity in refining in general will be a key factor to find ways to further improve energy efficiency of refining.
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| 64. |
- Karlström, Anders, 1958, et al.
(författare)
-
Refining models for control purposes
- 2008
-
Ingår i: Nordic Pulp and Paper Research Journal. - 2000-0669 .- 0283-2631. ; 23:1, s. 129-138
-
Tidskriftsartikel (refereegranskat)abstract
- Many studies have been carried out with the goalof improving pulp quality control in TMP refining processeswithout a deeper understanding about the physical conditionsinside the refining zone. The refiner is thereby considered as a black box where the chips are defibrated to fibers. In this paper, a non-linear model for the estimation of thermodynamic and defibration/fibrillation work is presented. It is shown that the model requires temperature measurements to span the energy balances and obtain reliable pressure gradients inside the refiningzone. Based on process data from a single disc refiner, it is shown that the defibration/fibrillation work varies substantially along the radius of the refining segments, even though the total work, i.e. the motor load, is almost the same over the specific time sequences. This is a consequence of variations in the concentration of the fiber pad built up inside the refining zone. Moreover, it is shown that the commonly used control concept, where the traditional specific energy is used as a control variableshould be reconsidered. Besides a deeper analysis about theassumptions made in the refiner modeling procedure, obtainedresults regarding estimated fiber concentration along the radius, consistency and steam efficiency are discussed.
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| 65. |
- Lindh, Roland, 1958-, et al.
(författare)
-
On the use of a Hessian model function in molecular geometry optimizations
- 1995
-
Ingår i: Chemical Physics Letters. - 0009-2614 .- 1873-4448. ; 241:4, s. 423-428
-
Tidskriftsartikel (refereegranskat)abstract
- When a molecular equilibrium geometry is determined by minimizing the energy by a quasi-Newton-Raphson method, the number of iterations required depends critically on the choice of an approximate molecular Hessian matrix. We find that a simple 15-parameter function of the nuclear positions gives a good choice for any molecule with atoms from the first three rows of the periodic table. This Hessian is used for ah initio geometry optimizations with the quasi-Newton-Raphson method, with or without update. The equilibrium geometries of 30 molecules, with a variety of sizes and symmetries, is obtained with the new scheme, which is shown to converge significantly faster than other methods.
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| 66. |
- Lindh, Roland, 1958-, et al.
(författare)
-
Research Article Extended ab Initio and Theoretical Thermodynamics Studies of the Bergman Reaction and the Energy Splitting of the Singlet o-, m-, and p-Benzynes
- 1995
-
Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 117:27, s. 7186-7194
-
Tidskriftsartikel (refereegranskat)abstract
- The autoaromatization of (Z)-hex-3-ene-1,5-diyne to the singlet biradical p-benzyne has been reinvestigated by state of the art ab initio methods. Previous CCSD(T)/6-31G(d,p) and CASPT2[0]/ANO[C(5s4p2dlf)/H(3s2p)] calculations estimated the reaction heat at 298 K to be 8-10 and 3.9 +/- 3.2 kcal/mol, respectively. Recent NO- and oxygen-dependent trapping experiments and collision-induced dissociation threshold energy experiments estimate the heat of reaction to be 8.5 +/- 1.0 kcal/mol at 470 K (corrected to 9.5 +/- 1.0 kcal/mol at 298 K) and 8.4 +/- 3.0 kcal/mol at 298 K, respectively. New theoretical estimates at 298 K predict the values at the basis set Limit for the CCSD(T) and CASPT2[gl] methods to be 12.7 +/- 2.0 and 5.4 +/- 2.0 kcal/mol, respectively. The experimentally predicted electronic contribution to the heat of activation is 28.6 kcal/mol. This can be compared with 25.5 and 29.8 kcal/mol from the CASPT2[gl] and the CCSD(T) methods, respectively. The new study has a much larger one-particle basis set for the CCSD(T) method as compared to earlier studies. For the CASPT2 investigation the better suited CASPT2[gl] approximation is utilized. The original CASPT2 method, CASPT2[0], systematically favors open-shell systems relative to closed-shell systems. This was previously corrected empirically. The current study shows that the energy difference between CCSD(T) and CASPT2[gl] at the basis set limit is estimated to be 7 +/- 2 kcal/mol. The study also demonstrates that the estimated heat of reaction is very sensitive to the quality of the basis set. In particular CCSD(T)/6-31G(d,p) approach underestimates the basis set limit of the enthalpy by approximately 5 kcal/mol. Furthermore, the relative energies of the p-, m-, and o-benzynes are computed at the CASPT2[gl] and CCSD(T) levels of theory. These results help to explain the discrepancy between the two methods in the case of the Bergman reaction. The deficiency of the CASPT2 method is mainly attributed to the approximate way in which the dynamic correlation is included by perturbation theory. A similar sized error is attributed to the CCSD(T) method due to the approximate way in which near degeneracy effects are included. This combined CCSD(T) and CASPT2[gl] study indicates that the most recent experimental value of the p-benzyne-o-benzyne energy splitting is overestimated.
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| 67. |
- Logenius, Louise, et al.
(författare)
-
Improved hydrogen peroxide bleaching of mechanical pulps using carbon dioxide in combination with sodium and magnesium based alkali sources
- 2011
-
Ingår i: 16th International Symposium on Wood, Fiber and Pulping Chemistry - Proceedings, ISWFPC. ; 1, s. 741-745, s. 741-745
-
Konferensbidrag (refereegranskat)abstract
- The pH-profile in the hydrogen peroxide bleaching stage of a Norway spruce thermomechanical pulp was levelled out by using carbon dioxide in combination with sodium or magnesium based alkali sources. Addition of carbon dioxide when magnesium hydroxide was used as the alkali source increased the pulp brightness with up to 1.5 brightness units when the bleaching was performed at 70 °C. When the temperature was increased from 70°C to 90 °C the brightness was increased with about two brightness units, addition of carbon dioxide increased it further. The residual hydrogen peroxide and the chemical oxygen demand (COD) levels were not affected as a consequence of the carbon dioxide addition. In the experiments where sodium hydroxide was used as the alkali source, addition of carbon dioxide lowered the pH that resulted in a decreased COD level, a slightly lower brightness level and, to some extent, an increased residual hydrogen peroxide level.
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| 68. |
- Lundström, Dag, 1968, et al.
(författare)
-
Transient identification using a fractional derivative model
- 1999
-
Ingår i: European Control Conference, ECC 1999 - Conference Proceedings. - : IEEE. - 9783952417355 ; , s. 2865 - 2868
-
Konferensbidrag (refereegranskat)abstract
- Characterizations, control or analyses of dynamic systems often demand low order models in order to be feasible. Dynamic system studies that involve phenomena such as in-elasticity or energy dissipation yields reasonably low order models when fractional derivatives is used. Properties of impulse responses from such models are presented. The results show that both frequency and envelope changes are functions of the derivative order and can thus be used in a function approximation. A suboptimal parameter estimator for such model is presented. © 1999 EUCA.
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| 69. |
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| 70. |
- Rosenqvist, Fredrik, 1972, et al.
(författare)
-
Controllability of direction dependent processes
- 2003
-
Ingår i: 42nd IEEE Conference on Decision and Control, 9-12 Dec. 2003.. - 0191-2216. - 0780379241 ; 4
-
Konferensbidrag (refereegranskat)abstract
- In a direction-dependent process, the dynamic response depends on the input or output direction. In this paper, controllability analysis of these processes investigates the ability to govern the output in any direction, even though the input signal is bounded. A sufficient condition for the controllability of single-input, single-output, direction-dependent processes is stated and proven.
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| 71. |
- Rosenqvist, Fredrik, 1972, et al.
(författare)
-
Direction-dependent system modeling approaches exemplified through an electronic nose system
- 2006
-
Ingår i: IEEE Transactions on Control Systems Technology. - 1063-6536 .- 1558-0865. ; 14:3, s. 526-531
-
Tidskriftsartikel (refereegranskat)abstract
- The modeling of processes exhibiting direction-dependent behavior is considered. Depending on the application, different models may be suitable. This brief is concerned with the use of Wiener models and piecewise-linear (PWL) models. These approaches are applied to data from an electronic nose system, for which knowledge of the physical principles is combined with system identification methods. Both models are found to provide close approximations to the behavior of the system itself. © 2006 IEEE.
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| 72. |
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| 73. |
- Rosenqvist, Fredrik, 1972, et al.
(författare)
-
Modelling a thermomechanical wood-chip refiner
- 2001
-
Ingår i: IASTED Conference. Modelling, Identification and Control, Innsbruck, Austria. ; II, s. 763 - 768
-
Konferensbidrag (refereegranskat)
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| 74. |
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| 75. |
- Rosenqvist, Fredrik, 1972, et al.
(författare)
-
PiEcewise-Linear Output-Error Methods for Parameter Estimation in Direction-Dependent Processes
- 2004
-
Ingår i: Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics). - Berlin, Heidelberg : Springer Berlin Heidelberg. - 1611-3349 .- 0302-9743. - 9783540212591 ; 2993, s. 493-507
-
Konferensbidrag (refereegranskat)abstract
- In direction-dependent processes, the dynamic responses depend on the direction of the system input. The parameter estimation of these processes under noisy conditions can be somewhat problematic in terms of predictor choice and asymptotic behaviour. For parameter estimation, a convenient way to model direction dependence is to use a piecewise-linear model formulation, whose switching depends on the input direction. This paper analyses a prediction-error minimisation method for direction-dependent processes in terms of piecewise-linear dynamics. In particular, the asymptotic convergence properties are investigated and relevant conditions for the utilisation of the estimation method are given. Further, it is demonstrated that a piecewise-linear output-error predictor is preferable in situations where the impact of disturbances is predominant. The main reason for this is that it separates the disturbances from the process model.
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| 76. |
- Rosenqvist, Fredrik, 1972, et al.
(författare)
-
Piecewise linear output-error models
- 2003
-
Ingår i: IFAC Symposium on System Identification, Rotterdam, the Netherlands.
-
Konferensbidrag (refereegranskat)
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| 77. |
- Rosenqvist, Fredrik, 1972, et al.
(författare)
-
Realisation and estimation of piecewise-linear output-error models
- 2005
-
Ingår i: Automatica. - : Elsevier BV. - 0005-1098. ; 41:3, s. 545-551
-
Tidskriftsartikel (refereegranskat)abstract
- Piecewise-linear systems in input/output form can have different switching schedules. In this article, two categories, instant and delayed switching, are analysed. Even though a general piecewise-linear state-space model cannot be converted into input/output form, it is shown that it is possible to find state-space models representing instant and delayed switching. In addition, a prediction-error minimisation (PEM) method for piecewise-linear output-error predictors is derived and it is concluded that the instant-switching model candidate is not necessarily the most suitable for the parameter estimation procedure.
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| 78. |
- Rosenqvist, Fredrik, 1972, et al.
(författare)
-
Time-variant modelling of TMP refining
- 2001
-
Ingår i: IEEE IAS Workshop on Advanced Process Control. ; , s. 37-42
-
Konferensbidrag (refereegranskat)
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| 79. |
- Sikter, David, et al.
(författare)
-
Using the refining zone temperature profile for quality control
- 2007
-
Ingår i: International Mechanical Pulping Conference 2007, TAPPI. - Atlanta, GA : TAPPI Press. - 9781605602936 ; , s. 894-902
-
Konferensbidrag (refereegranskat)abstract
- ABSTRACT To achieve good quality control in TMP refining, relevant information about the process is needed. In this paper, the refining zone temperature profile has been studied to investigate if this information can be used to stabilize the pulp quality. The studied system is a commercial RTS primary refiner at Hallsta Paper mill. The response of the temperature profile was examined and compared with the pulp quality disturbances after both the first and second stage. The disturbances in the radial position of the temperature peak were found to be strongly correlated with the disturbances in freeness and mean fiber length. Based on these results, a new control strategy was designed to keep the peak position constant by changing the inlet pressure. This new control strategy decreased the freeness disturbances compared to the mill�s normal strategy, and analysis suggests that the disturbances could be further reduced by including also the maximum temperature in the control concept. The potential of improvement in terms of reduced standard deviation of CSF was estimated to 11% or more. The comparison indicates that temperature parameters are better than the commonly used specific energy when it comes to predicting and reducing these quality disturbances.
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| 80. |
- Sund, Johan, et al.
(författare)
-
The effect of process design on refiner pulp quality control performance
- 2021
-
Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 36:4, s. 594-607
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, the effect of process- and online analyser configuration on pulp quality control is explored. The following parameters were included: analyser sampling interval, time delay, measurement error magnitude, and latency chest residence time. Using different values of parameters in a process model, a range of configurations were constructed. For each configuration, the achievable control performance was evaluated using an optimization approach. PI controller settings were chosen based on minimization of the integrated absolute error (IAE) in pulp quality after an input step disturbance. The results show that reducing the sampling interval improves performance also when the interval is smaller than the chest residence time or the analyser delay. Moreover, reducing the chest residence time can reduce the IAE by up to 40 %. However, reducing the residence time to lower than 1/3 of the sampling interval does not improve performance. Further improvement is possible if the analyser delay is reduced. The compromise between reducing the IAE and avoiding creating variation by acting on measurement error has a strong influence on the results. In conclusion, pulp quality control performance can be improved significantly by making changes to the studied configuration parameters.
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| 81. |
- Wanngren, Johanna, et al.
(författare)
-
Second generation γ-secretase modulators exhibit different modulation of Notch β and Aβ production.
- 2012
-
Ingår i: The Journal of biological chemistry. - 1083-351X. ; 287:39, s. 32640-50
-
Tidskriftsartikel (refereegranskat)abstract
- The γ-secretase complex is an appealing drug target when the therapeutic strategy is to alter amyloid-β peptide (Aβ) aggregation in Alzheimer disease. γ-Secretase is directly involved in Aβ formation and determines the pathogenic potential of Aβ by generating the aggregation-prone Aβ42 peptide. Because γ-secretase mediates cleavage of many substrates involved in cell signaling, such as the Notch receptor, it is crucial to sustain these pathways while altering the Aβ secretion. A way of avoiding interference with the physiological function of γ-secretase is to use γ-secretase modulators (GSMs) instead of inhibitors of the enzyme. GSMs modify the Aβ formation from producing the amyloid-prone Aβ42 variant to shorter and less amyloidogenic Aβ species. The modes of action of GSMs are not fully understood, and even though the pharmacology of GSMs has been thoroughly studied regarding Aβ generation, knowledge is lacking about their effects on other substrates, such as Notch. Here, using immunoprecipitation followed by MALDI-TOF MS analysis, we found that two novel, second generation GSMs modulate both Notch β and Aβ production. Moreover, by correlating S3-specific Val-1744 cleavage of Notch intracellular domain (Notch intracellular domain) to total Notch intracellular domain levels using immunocytochemistry, we also demonstrated that Notch intracellular domain is not modulated by the compounds. Interestingly, two well characterized, nonsteroidal anti-inflammatory drugs (nonsteroidal anti-inflammatory drug), R-flurbiprofen and sulindac sulfide, affect only Aβ and not Notch β formation, indicating that second generation GSMs and nonsteroidal anti-inflammatory drug-based GSMs have different modes of action regarding Notch processing.
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