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| 2. |
- Bengtsson, Fredrik, 1989, et al.
(författare)
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Modeling of tensile index using uncertain data sets
- 2020
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Ingår i: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 2000-0669 .- 0283-2631. ; 35:2, s. 231-242
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this investigation is to analyze and model tensile index. Two approaches are used, one based on training and validation data, while the other novel approach tests models using all possible combinations of data points. This approach is focused on small data sets which have here been obtained from nineteen pulp samples at different refining conditions in a full-scale TMP production line with a CD-76 refiner as a primary stage. From each pulp sample twenty handsheet strips for tensile index measurements were performed. Initially, specific energy and the external variables (dilution water feed rates and plate gaps) are used as predictors in a modeling approach based on an adjusted R 2 {R^{2}} approach. Thereafter, the resulting models are compared with a combination of specific energy and internal variables (primarily consistencies) obtained from temperature measurements inside the refining zones using a soft sensor concept. It is found that specific energy and internal variables as predictors outperform the external variables when estimating tensile index.
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| 3. |
- Bengtsson, Fredrik, 1989, et al.
(författare)
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On the modeling of pulp properties in CTMP processes
- 2021
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Ingår i: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 2000-0669 .- 0283-2631. ; 36:2, s. 234-248
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Tidskriftsartikel (refereegranskat)abstract
- The goal of this paper is to model the pulp properties fiber length, shives width and freeness. This will be done utilizing specific energy, flat zone inlet consistency and the internal variables, consistencies and fiber residence times estimated from refining zone soft sensors. The models are designed using more than 3600 hours of data from a RGP82CD refiner. The pulp properties are sampled using a measurement device positioned after the latency chest. Such measurements are noisy and irregularly sampled which opens for a number of challenges to overcome in modeling procedures. In this paper it is shown that the models for shives width and fiber length are capable of predicting most of the major dynamics. However, for freeness no reliable linear models can be derived. When estimating fiber length, the specific energy together with flat zone inlet consistency, fiber residence times and the consistency in the conical zone were the dominant inputs. For shives width it was found that a similar set of inputs resulted in the best models, except that the consistencies during normal process conditions did not significantly influence shives width. Furthermore, fiber residence times were shown to have considerably more pronounced impact on fiber length compared with shives width estimates.
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| 4. |
- Fredriksson, Joel, et al.
(författare)
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Analyzing non-linear contributions to predictive performance in a neural network based scheduling model
- 2023
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Ingår i: Proceedings 14th International Conference on Ambient Systems, Networks and Technologies Networks, ANT 2023 and The 6th International Conference on Emerging Data and Industry 4.0, EDI40 2023. - : Elsevier BV. ; , s. 680-685
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Konferensbidrag (refereegranskat)abstract
- This paper aims to investigate whether increasing non-linear opportunities in a neural network-based scheduling model improves its predictive performance. More specifically, this paper experiments on a trip distribution model that is part of an activity-based scheduling model called Skyline-seqNN from the ongoing thesis A neural network scheduling model. The motivation behind that model s proposed structure is to lay the groundwork for a neural network discrete choice model (DCM) that achieves to model travel demand on a detailed level while also being suitable for experimental analysis. Similar to a four-step model framework in the sequential aspect, the model system from the referenced paper utilizes the three sub-models; trip generation, trip distribution, and mode choice using a utility-maximizing micro-simulation approach. The trip generation model first decides whether, at every 10-minute interval between 05:00 am and 11:00 pm, an individual in the next time step should stay and continue the current activity or take an activity-defined trip. The distribution and mode choice models are used whenever a trip is selected. The trip distribution model decides the trip s destination by evaluating travel times and land use descriptions of each zone. The mode choice model learns the probability distribution of modes given each mode s travel time to the selected destination zone. Tests performed in this paper show how successive non-linear opportunities between input features in the trip distribution model increase its predictive performance. The data used for training and evaluation comes from a travel questionnaire from 2015 per-formed in Stockholm containing 10819 individuals and days.
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| 5. |
- Karlström, Anders, 1958, et al.
(författare)
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Data-Driven Soft Sensors in Pulp Refining Processes Using Artificial Neural Networks
- 2024
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Ingår i: BioResources. - 1930-2126 .- 1930-2126. ; 19:1, s. 1030-1057
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Tidskriftsartikel (refereegranskat)abstract
- Pulp refining processes are most often complicated to describe using linear methodologies, and sometimes an artificial neural network (ANN) is a preferable alternative when assimilating non-linear operating data. In this study, an ANN is used to predict pulp properties, such as shives (wide), fiber length, and freeness. Both traditional process variables (external variables) and refining zone variables (internal variables) are necessary to include as model inputs. The estimation of shives (wide) results achieved an R2 (coefficient of determination) of 0.9 (0.7) for the training and (validation) sets. Corresponding measures for fiber length and freeness can be questioned using this methodology. It is shown that the maximum temperature in the flat zone can be modeled using the external variables motor load and production instead of the specific energy. This resulted in an R2 of approximately 0.9 for the training sets, while the R2 for the validation set did not reach an acceptable level – most likely due to inherent non-linearities in the process. Additional results showed that the consistency profile is difficult to estimate properly using an ANN. Instead, a model-driven sensor is preferred to be used. The main results from this study indicate that shives (wide) should be the prime candidate when introducing advanced pulp property control concepts.
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| 6. |
- Karlström, Anders, 1958, et al.
(författare)
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Data-Driven Soft Sensors in Refining Processes – Pulp Property Estimation Using ARX-Models
- 2023
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Ingår i: BioResources. - 1930-2126 .- 1930-2126. ; 18:4, s. 8163-8186
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Tidskriftsartikel (refereegranskat)abstract
- This paper focuses on estimation of shives(wide) and fiber length in RGP82CD-refiners using an AutoRegressive eXogenous (ARX) structure in a data-driven soft sensor concept. Both external and internal variables are considered as model inputs. The pulp properties were sampled every 15 min from an on-line device positioned after the latency chest, whereas other process data were sampled every 6 seconds. Notably, despite the high data sampling rate, the development of robust models necessitated a dataset spanning over two months of process information. The external variables studied in this paper were specific energy, the sawmill chip content, plate gaps, and dilution water feed rates to each refining zone. Additional internal variables, such as the inlet flat zone temperature, the maximum temperature, and the periphery temperature in the conical zone, were also used as model inputs. It was concluded that both shives(wide) and fiber length can be estimated with relatively good accuracy although large uncertainties exist in the measured properties. Finally, it was shown that fast pulp property dynamics in the blow-line can be followed, which outperforms current practices of using pulp measurement devices positioned after the latency chest. This offers implementation of more advanced future pulp property control concepts.
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| 7. |
- McCarthy, Stephen, et al.
(författare)
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Linking mode with activity purpose in a dynamic scheduling model
- 2023
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Ingår i: Proceedings 14th International Conference on Ambient Systems, Networks and Technologies Networks, ANT 2023 and The 6th International Conference on Emerging Data and Industry 4.0, EDI40 2023. - : Elsevier BV. ; , s. 674-679
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Konferensbidrag (refereegranskat)abstract
- This paper improves a dynamic scheduling model, Scaper, by including dependence between agents' mode choice and activity purpose. Observed differences in mode share across activity purposes are likely caused both by factors endogenous to the model such as differing levels of service by time of day or geography, and by factors which cannot be represented endogenously with the data available, such as perceived travel needs. The updated model introduces joint purpose- and mode-dependent parameters to account for these exogenous factors. The model improves on a reference model without joint parameters on mode share predictions of activities of different purposes, providing advantages for use in activity purpose-sensitive policy evaluation.
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| 8. |
- Myrhammar, Anders, et al.
(författare)
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Evaluation of an antibody-PNA conjugate as a clearing agent for antibody-based PNA-mediated radionuclide pretargeting
- 2020
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- Radionuclide molecular imaging of cancer-specific targets is a promising method to identify patients for targeted antibody therapy. Radiolabeled full-length antibodies however suffer from slow clearance, resulting in high background radiation. To overcome this problem, a pretargeting system based on complementary peptide nucleic acid (PNA) probes has been investigated. The pretargeting relies on sequential injections of primary, PNA-tagged antibody and secondary, radiolabeled PNA probe, which are separated in time, to allow for clearance of non-bound primary agent. We now suggest to include a clearing agent (CA), designed for removal of primary tumor-targeting agent from the blood. The CA is based on the antibody cetuximab, which was conjugated to PNA and lactosaminated by reductive amination to improve hepatic clearance. The CA was evaluated in combination with PNA-labelled trastuzumab, T-ZHP1, for radionuclide HER2 pretargeting. Biodistribution studies in normal mice demonstrated that the CA cleared ca. 7 times more rapidly from blood than unmodified cetuximab. Injection of the CA 6 h post injection of the radiolabeled primary agent [131I]I-T-ZHP1 gave a moderate reduction of the radioactivity concentration in the blood after 1 h from 8.5 ± 1.8 to 6.0 ± 0.4%ID/g. These proof-of-principle results could guide future development of a more efficient CA.
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| 9. |
- Myrhammar, Anders, 1987-
(författare)
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Investigations of chemical and enzymatic functionalization of affinity proteins
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- AbstractAffinity proteins are important reagents in research, diagnostics and therapeutic settings. The focus of this thesis has been on investigating different chemical and enzymatic strategies for engineering of affinity proteins to generate affinity reagents with improved or changed functionality. The modifications introduced in affibodies, representing a class of small, three-helix engineered scaffold proteins, and antibodies were selected and implemented through rational design, using a combination of solid phase peptide synthesis, genetic engineering and enzymatic conjugation, depending on the case.In a first study, thioether crosslinks were introduced between internally positioned lysines and cysteines of the human epidermal growth factor receptor (hEGFR)-targeting affibody ZEGFR:1907, to test the possibility to increase the proteolytic stability of the affibody scaffold. Three different variants of crosslinked affibodies were produced, containing one or two crosslinks. All three variants showed similar affinities to EFGR, and secondary structure contents, as the unmodified control protein. The crosslinked affibodies were challenged with the endopeptidases pepsin, found in the stomach, and trypsin and chymotrypsin, found in the gut. All affibodies showed improved stability towards at least one of the proteases, but the largest improvement was seen for the affibody harboring two crosslinks, which displayed the greatest stability in both assays.Improvement in proteolytic stability of affibodies was further explored. In another study a sortase A-catalyzed intramolecular head-to-tail conjugation of the dimeric human epidermal growth factor 2 (HER2)-targeting affibody (ZHER2:342)2 was performed. Analysis showed no change in α-helicity for the cyclic dimer compared to the linear control, and a slight increase in melting temperature. Interestingly, in contrast to the linear variant, the cyclic dimer showed no signs of proteolytic degradation after 60 min exposure to the exopeptidase carboxypeptidase A.The ability to change protein functionality by chemical modification was explored in two studies. The immunoglobulin-binding Z domain, from which the affibody scaffold is derived, was used as a model protein in one study, where light-induced affinity modulation was investigated. An azobenzene switch that isomerizes from a trans to a cis state was introduced end-to-end to one of the helices in three different designs of the Z domain. The conformational change induced by isomerization was hypothesized to be large enough to cause a loss in binding affinity in the conjugated affibody, which was tested in an affinity chromatography assay in which one of the affibodies captured to an IgG-sepharose column showed loss of affinity during illumination.Peptide nucleic acid (PNA) probes have previously successfully been used for selective hybridization between the primary, tumor-targeting agent and the secondary agent in a pretargeting set-up for in vivo tumor imaging or directed therapy. In a last study, a Z domain-PNA conjugate produced via sortase A-mediated conjugation was photoconjugated to a lactosaminated antibody for possible use as an in vivo clearing agent for clearance of excess of primary probes via an hepatic route. The clearing agent showed partial success in a mouse model but the concept needs further work.The work in this thesis shows the diverse possibilities available for changing the functionality of affinity proteins through chemical and enzymatic methods for different applications, and provides a framework for potential further improvement of both affibody and antibody functionality.
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| 10. |
- Myrhammar, Anders, et al.
(författare)
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Photocontrolled Reversible Binding between the Protein A-Derived Z Domain and Immunoglobulin G
- 2020
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Ingår i: Bioconjugate chemistry. - : American Chemical Society (ACS). - 1043-1802 .- 1520-4812. ; 31:3, s. 622-630
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Tidskriftsartikel (refereegranskat)abstract
- Photoisomerization of the trans and cis isomers of azobenzene derivatives has been used to control the function of biomolecules in a reversible and nondestructive manner. In this study, affibody molecules, representing a class of small, helical proteins that can be engineered for binding to a wide range of target proteins, have been investigated by the incorporation of a photoswitchable azobenzene derivative in the molecule. Three different Z domain variants were produced by solid phase peptide synthesis and conjugated by thiol-directed chemistry to an azobenzene-based photoswitch. The proteins were screened for binding to and light elution from an IgG-sepharose affinity column. One of the tested Z variants, Z(C3), showed efficient binding to the column and could be eluted by irradiation with light at 400 nm. In a reverse affinity chromatography assay, where the Z(C3) variant was coupled to sepharose, human IgG1 could be captured to the column and partially eluted by light. Further studies of the azobenzene-conjugated Z(C3) domain by surface plasmon resonance (SPR) confirmed the high affinity binding to IgG, and circular dichroism (CD) spectroscopy showed that the protein has a high alpha-helical secondary structure content.
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