liu.seSearch for publications in DiVA
1 - 4 of 4
rss atomLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
  • Public defence: 2020-02-28 09:15 Planck, F Building, Linköping
    Persson, Mia
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, Faculty of Science & Engineering.
    Pawsitive selection: Genetics of dog-human communication2020Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Through domestication and recent selection, dogs have evolved a unique set of communicative skills to attract and redirect human attention. These social skills have not been seen to the same extent in socialised wolves and are therefore believed to have a significant genetic basis. The process of domestication and breed formation has also had effects on the structure of the dog genome that are favourable for genetic mapping. With a high amount of linkage and long haplotype blocks, fewer genetic markers are needed to find gene-trait associations in dogs than in humans. Dogs serve as an important research model for us since humans and dogs share several diseases, psychiatric disorders and behavioural traits.

    In Paper I, I recorded human-directed social behaviours during a two-minute unsolvable problem task in 500 laboratory beagles. The dogs were living at a breeding facility and had been bred, kept and handled under standardised conditions. Behaviours related to task solving and human-directed contact seeking were separated in a principal component analysis, indicating that the behavioural test can be used to study dog-human interaction. Narrowsense heritability (h2) of the largest principal component related to contact seeking behaviours was estimated to 0.23. This study found a significant genetic basis to the variation seen in human-directed contact seeking behaviours recorded in this population.

    Next, in Paper II, we collected and genotyped the DNA of 190 of the previously tested beagles with an HD Canine SNP-chip. To find genes associated with human-directed contact seeking I performed a genome-wide association study (GWAS), showing one significant and two suggestive single nucleotide polymorphism (SNP) markers on chromosome 26. The significant SNP is located within a gene named SEZ6L, previously associated with autism in human studies. Two adjacent SNPs with suggestive association were found within a gene called ARVCF, which has been associated with schizophrenia. To our knowledge, this was the first genome-wide study to present regions within the dog genome associated with inter-species communication in dogs.

    However, these results could have been unique to this beagle population, so Paper III aimed to verify our previous findings in additional dog breeds. We tested 100 Labrador retrievers and 61 golden retrievers with the same unsolvable problem-task used in Paper I. Their DNA was collected and each individual was genotyped by pyrosequencing on two of the previously identified SNPs. To study the effects of recent selection, the Labrador retrievers were divided into two types. The common type is mainly bred and used for dog shows and as a pet, while the field type is mainly bred and used for hunting purposes. In this study, we found that both markers varied in both dog breeds and was significantly associated with human-directed contact-seeking behaviours. Allele frequencies differed significantly between Labrador retriever types, suggesting that these loci have been affected by recent selection. In conclusion, Paper III verifies the results found in Paper II.

    Finally, in Paper IV we investigated the association between dogs’ human-directed social skills and previously known SNP markers in the oxytocin receptor (OXTR) region. The oxytocin system plays an important role in the formation of social bonds and may therefore also be important in the bond between dogs and humans. Here, we hypothesized that dogs receiving intranasal oxytocin respond differently to the hormone, depending on the receptor type. To investigate this, 60 golden retrievers were genotyped for SNP markers in the OXTR region and tested with the unsolvable problem task used in Paper I and III. An association was found between genotype and social behaviour in response to oxytocin administration. Dogs responded differently to oxytocin treatment, depending on OXTR genotype. In summary, this thesis contributes to the knowledge on genetic influence of interspecies communication in dogs.

    List of papers
    1. Human-directed social behaviour in dogs shows significant heritability
    Open this publication in new window or tab >>Human-directed social behaviour in dogs shows significant heritability
    Show others...
    2015 (English)In: Genes, Brain and Behavior, ISSN 1601-1848, E-ISSN 1601-183X, Vol. 14, no 4, p. 337-344Article in journal (Refereed) Published
    Abstract [en]

    Through domestication and co-evolution with humans, dogs have developed abilities to attract human attention, e.g. in a manner of seeking assistance when faced with a problem solving task. The aims of this study were to investigate within breed variation in human-directed contact seeking in dogs and to estimate its genetic basis. To do this, 498 research beagles, bred and kept under standardized conditions, were tested in an unsolvable problem task. Contact seeking behaviours recorded included both eye contact and physical interactions. Behavioural data was summarized through a principal component analysis, resulting in four components: test interactions, social interactions, eye contact and physical contact. Females scored significantly higher on social interactions and physical contact and age had an effect on eye contact scores. Narrow sense heritabilities (h2) of the two largest components were estimated at 0.32 and 0.23 but were not significant for the last two components. These results show that within the studied dog population, behavioural variation in human-directed social behaviours was sex dependent and that the utilization of eye contact seeking increased with age and experience. Hence, heritability estimates indicate a significant genetic contribution to the variation found in human-directed social interactions, suggesting that social skills in dogs have a genetic basis, but can also be shaped and enhanced through individual experiences. This research gives the opportunity to further investigate the genetics behind dogs’ social skills, which could also play a significant part into research on human social disorders such as autism.

    Place, publisher, year, edition, pages
    John Wiley & Sons, 2015
    Keywords
    Beagles, canine behaviour, dogs, domestic dog, eye contact, genetics, heritability, human-directed communication, problem-solving, social behaviour
    National Category
    Human Computer Interaction
    Identifiers
    urn:nbn:se:liu:diva-117523 (URN)10.1111/gbb.12194 (DOI)000353405000003 ()25703740 (PubMedID)
    Funder
    EU, European Research Council, 1242001390
    Available from: 2015-04-30 Created: 2015-04-30 Last updated: 2020-01-21
    2. Genomic Regions Associated With Interspecies Communication in Dogs Contain Genes Related to Human Social Disorders
    Open this publication in new window or tab >>Genomic Regions Associated With Interspecies Communication in Dogs Contain Genes Related to Human Social Disorders
    Show others...
    2016 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, article id 33439Article in journal (Refereed) Published
    Abstract [en]

    Unlike their wolf ancestors, dogs have unique social skills for communicating and cooperating with humans. Previously, significant heritabilities for human-directed social behaviors have been found in laboratory beagles. Here, a Genome-Wide Association Study identified two genomic regions associated with dog's human-directed social behaviors. We recorded the propensity of laboratory beagles, bred, kept and handled under standardized conditions, to initiate physical interactions with a human during an unsolvable problem-task, and 190 individuals were genotyped with an HD Canine SNP-chip. One genetic marker on chromosome 26 within the SEZ6L gene was significantly associated with time spent close to, and in physical contact with, the human. Two suggestive markers on chromosome 26, located within the ARVCF gene, were also associated with human contact seeking. Strikingly, four additional genes present in the same linkage blocks affect social abilities in humans, e.g., SEZ6L has been associated with autism and COMT affects aggression in adolescents with ADHD. This is, to our knowledge, the first genome-wide study presenting candidate genomic regions for dog sociability and inter-species communication. These results advance our understanding of dog domestication and raise the use of the dog as a novel model system for human social disorders.

    Place, publisher, year, edition, pages
    Nature Publishing Group, 2016
    National Category
    Genetics
    Identifiers
    urn:nbn:se:liu:diva-131644 (URN)10.1038/srep33439 (DOI)000384172800001 ()27685260 (PubMedID)
    Note

    Funding agencies: European Research Council (ERC) [322206]; Formas

    Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2020-01-21Bibliographically approved
    3. Sociality genes are associated with human-directed social behaviour in golden and Labrador retriever dogs
    Open this publication in new window or tab >>Sociality genes are associated with human-directed social behaviour in golden and Labrador retriever dogs
    Show others...
    2018 (English)In: PeerJ, ISSN 2167-8359, E-ISSN 2167-8359, Vol. 6, article id e5889Article in journal (Refereed) Published
    Abstract [en]

    Background: Dogs have human-directed social skills that allow them to communicate and cooperate with humans. We have previously identified two loci on chromosome 26 associated with human contact-seeking behaviors during an unsolvable problem task in laboratory beagles (Persson et A, 2016). The aim of the present study was to verify the single nucleotide polymorphisms (SNPs) in additional dog breeds. We also studied how the allele frequencies have changed during domestication and recent selection. Methods: Dogs of two breeds, 61 golden retrievers and 100 Labrador retrievers, were phenotyped and genotyped, and 19 wolves were genotyped. The Labrador retrievers were divided into common and field type by pedigree data to make it possible to study the effects of recent selection. All dogs were tested in an unsolvable problem task where human-directed social behaviors were scored. DNA from dogs (buccal swabs) and wolves (blood or brain tissue) was analyzed for genotype on two of the previously identified SNP markers, BICF2G630798942 (SNP1) and BICF2S23712114 (SNP2), by pyrosequencing. Results: There was genetic variation for SNP1 in both dog breeds whereas the wolves were fixed for this polymorphism, and for SNP2 there was variation in both dogs and wolves. For both SNPs, Labrador retriever types differed significantly in allele frequencies. We found associations between SNPs and human-directed social behavior in both dog breeds. In golden retrievers, SNP I was associated with physical contact variables, for example, with the duration of physical contact with the owner (F-2,F-56 = 4.389, p = 0.017). SNP2 was associated with several behavioral variables in both breeds, among others owner gazing frequency in both golden retrievers (F-2,F-55 = 6.330, p = 0.003) and Labradors (F-1,F-93 = 5.209, p = 0.025). Discussion: Our results verify the association between the previously identified SNPs and human-directed social behavior scored in an unsolvable problem task. Differences in allele frequencies suggest that these loci have been affected by selection. The results indicate that these genomic regions are involved in human-directed social behavior in not only beagles but in other dog breeds as well. We hypothesize that they may have been important during dog domestication.

    Place, publisher, year, edition, pages
    PEERJ INC, 2018
    Keywords
    Genetics; Dog genetics; Dog behavior; Human-dog communication; Human-directed social behavior; Golden retrievers; Labrador retrievers; Wolf; Domestication; Behavior genetics
    National Category
    Evolutionary Biology
    Identifiers
    urn:nbn:se:liu:diva-153536 (URN)10.7717/peerj.5889 (DOI)000452327000008 ()30416887 (PubMedID)
    Note

    Funding Agencies|European Research Council (ERC) [322206]

    Available from: 2018-12-20 Created: 2018-12-20 Last updated: 2020-01-21
    4. Intranasal oxytocin and a polymorphism in the oxytocin receptor gene are associated with human-directed social behavior in golden retriever dogs
    Open this publication in new window or tab >>Intranasal oxytocin and a polymorphism in the oxytocin receptor gene are associated with human-directed social behavior in golden retriever dogs
    Show others...
    2017 (English)In: Hormones and Behavior, ISSN 0018-506X, E-ISSN 1095-6867, Vol. 95, p. 85-93Article in journal (Refereed) Published
    Abstract [en]

    The oxytocin system may play an important role in dog domestication from the wolf. Dogs have evolved unique human analogue social skills enabling them to communicate and cooperate efficiently with people. Genomic differences in the region surrounding the oxytocin receptor (OXTR) gene have previously been associated with variation in doge communicative skills. Here we have utilized the unsolvable problem paradigm to investigate the effects of oxytocin and OXTR polymorphisms on human-directed contact seeking behavior in 60 golden retriever dogs. Human-oriented behavior was quantified employing a previously defined unsolvable problem paradigm. Behaviors were tested twice in a repeated, counterbalanced design, where dogs received a nasal dose of either oxytocin or saline 45 min before each test occasion. Buccal DNA was analysed for genotype on three previously identified SNP-markers associated with OXTR. The same polymorphisms were also geno-typed in 21 wolf blood samples to explore potential genomic differences between the species. Results showed that oxytocin treatment decreased physical contact seeking with the experimenter and one of the three polymorphisms was associated with degree of physical contact seeking with the owner. Dogs with the AA-genotype at this locus increased owner physical contact seeking in response to oxytocin while the opposite effect was found in GG-genotype individuals. Hence, intranasal oxytocin treatment, an OXTR polymorphism and their interaction are associated with doge human-directed social skills, which can explain previously described breed differences in oxytocin response. Genotypic variation at the studied locus was also found in wolves indicating that it was present even at the start of dog domestication.

    Place, publisher, year, edition, pages
    ACADEMIC PRESS INC ELSEVIER SCIENCE, 2017
    Keywords
    Oxytocin; Oxytocin receptor gene; OXTR; Domestic dog; Canine; Wolf; Canis lupus; Behavior genetics; Canine behavior; Social behavior
    National Category
    Other Biological Topics
    Identifiers
    urn:nbn:se:liu:diva-142438 (URN)10.1016/j.yhbeh.2017.07.016 (DOI)000412863500010 ()28765081 (PubMedID)
    Note

    Funding Agencies|European Research Council (ERC) [322206]

    Available from: 2017-10-31 Created: 2017-10-31 Last updated: 2020-01-21
  • Public defence: 2020-02-28 10:15 K3, Kåkenhus, Norrköping
    Shiran Chaharsoughi, Mina
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Hybrid Plasmonics for Energy Harvesting and Sensing of Radiation and Heat2020Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The special optical properties of subwavelength metallic structures have opened up for numerous applications in different fields. The interaction of light with metal nanostructures leads to the excitation of collective oscillations of conduction-band electrons, known as plasmons. These plasmon excitations are responsible for the high absorption and high scattering of light in metallic nanostructures. High absorption of light and the subsequent temperature increase in the nanostructures make them suitable as point-like heat sources that can be controlled remotely by light.

    The research presented in this thesis focuses on the development and studies of hybrid devices that combine light-induced heating in plasmonic nanostructures with other materials and systems. Particular focus is put on hybrid organic-inorganic systems for applications in energy harvesting as well as in heat and radiation sensing. Harvesting energy from light fluctuations was achieved in a hybrid device consisting of plasmonic gold nanodisk arrays and a pyroelectric copolymer. In this concept, fast and efficient light-induced heating in the gold nanodisks modulated the temperature of the pyroelectric layer, which could be used to extract electrical energy from fluctuations in simulated sunlight.

    Integrating plasmonic nanostructures with complementary materials can also provide novel hybrid sensors, for monitoring of temperature, heat flux and radiation. In this thesis work, a hybrid sensor was designed based on the combination of a plasmonic gold nanohole layer with a pyroelectric copolymer and an ionic thermoelectric gel. The gold nanohole arrays acted both as broadband light absorbers in the visible to near-infrared spectral range of the solar spectrum and also as one of the electrodes of the sensor. In contrast to the constituent components when used separately, the hybrid sensor could provide both fast and stable signals upon heat or radiation stimuli, as well as enhanced equilibrium signals.

    Furthermore, a concept for heat and radiation mapping was developed that was highly sensitive and stable despite its simple structure. The concept consisted of a gel-like electrolyte connecting two separated metal nanohole electrodes on a substrate. Resembling traditional thermocouples, this concept could autonomously detect temperature changes but with several orders of magnitudes higher sensitivity. Owing to its promising sensing properties as well as its compatibility with inexpensive mass production methods on flexible substrates, such concept may be particularly interesting for electronic skin applications for health monitoring and for humanoid robotics. Finally, we improved the possibilities for the temperature mapping of the concept by modifying the structure from lateral to vertical form. Similar to the lateral device, the vertical temperature sensor showed high temperature sensitivity and stability in producing signals upon temperature changes.

    List of papers
    1. Hybrid Plasmonic and Pyroelectric Harvesting of Light Fluctuations
    Open this publication in new window or tab >>Hybrid Plasmonic and Pyroelectric Harvesting of Light Fluctuations
    Show others...
    2018 (English)In: Advanced Optical Materials, ISSN 2162-7568, E-ISSN 2195-1071Article in journal (Refereed) Published
    Abstract [en]

    State-of-the-art solar energy harvesting systems based on photovoltaic technology require constant illumination for optimal operation. However, weather conditions and solar illumination tend to fluctuate. Here, a device is presented that extracts electrical energy from such light fluctuations. The concept combines light-induced heating of gold nanodisks (acting as plasmonic optical nanoantennas), and an organic pyroelectric copolymer film (poly(vinylidenefluoride-co-trifluoroethylene)), that converts temperature changes into electrical signals. This hybrid device can repeatedly generate current pulses, not only upon the onset of illumination, but also when illumination is blocked. Detailed characterization highlights the key role of the polarization state of the copolymer, while the copolymer thickness has minor influence on performance. The results are fully consistent with plasmon-assisted pyroelectric effects, as corroborated by combined optical and thermal simulations that match the experimental results. Owing to the tunability of plasmonic resonances, the presented concept is compatible with harvesting near infrared light while concurrently maintaining visible transparency.

    Place, publisher, year, edition, pages
    Wiley-Blackwell, 2018
    Keywords
    Gold nanodisks, Plasmonic heating, Pyroelectric copolymers, Solar energy harvesting
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-148574 (URN)10.1002/adom.201701051 (DOI)000434349300001 ()
    Note

    Funding agencies: Wenner-Gren Foundations; Swedish Research Council [2015-05070]; Swedish Foundation for Strategic Research; AForsk Foundation; Royal Swedish Academy of Sciences; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Lin

    Available from: 2018-06-13 Created: 2018-06-13 Last updated: 2020-01-31
    2. Thermodiffusion-Assisted Pyroelectrics-Enabling Rapid and Stable Heat and Radiation Sensing
    Open this publication in new window or tab >>Thermodiffusion-Assisted Pyroelectrics-Enabling Rapid and Stable Heat and Radiation Sensing
    Show others...
    2019 (English)In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 29, no 28, article id 1900572Article in journal (Refereed) Published
    Abstract [en]

    Sensors for monitoring temperature, heat flux, and thermal radiation are essential for applications such as electronic skin. While pyroelectric and thermoelectric effects are suitable candidates as functional elements in such devices, both concepts show individual drawbacks in terms of zero equilibrium signals for pyroelectric materials and small or slow response of thermoelectric materials. Here, these drawbacks are overcome by introducing the concept of thermodiffusion-assisted pyroelectrics, which combines and enhances the performance of pyroelectric and ionic thermoelectric materials. The presented integrated concept provides both rapid initial response upon heating and stable synergistically enhanced signals upon prolonged exposure to heat stimuli. Likewise, incorporation of plasmonic metasurfaces enables the concept to provide both rapid and stable signals for radiation-induced heating. The performance of the concept and its working mechanism can be explained by ion-electron interactions at the interface between the pyroelectric and ionic thermoelectric materials.

    Place, publisher, year, edition, pages
    Wiley-VCH Verlagsgesellschaft, 2019
    Keywords
    heat sensing; ionic thermodiffusion; plasmonic heating; pyroelectric copolymer
    National Category
    Other Materials Engineering
    Identifiers
    urn:nbn:se:liu:diva-159730 (URN)10.1002/adfm.201900572 (DOI)000478851700007 ()2-s2.0-85064476505 (Scopus ID)
    Note

    Funding Agencies|Swedish Foundation for Strategic Research; Swedish Research Council; AForsk Foundation; Wenner-Gren Foundations; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [200900971]

    Available from: 2019-08-19 Created: 2019-08-19 Last updated: 2020-01-31Bibliographically approved
  • Public defence: 2020-03-06 10:15 Ada Lovelace, Building B, Linköping
    Voronov, Sergii
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Machine Learning Models for Predictive Maintenance2020Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The amount of goods produced and transported around the world each year increases and heavy-duty trucks are an important link in the logistic chain. To guarantee reliable delivery a high degree of availability is required, i.e., avoid standing by the road unable to continue the transport mission. Unplanned stops by the road do not only cost due to the delay in delivery, but can also lead to damaged cargo. Vehicle downtime can be reduced by replacing components based on statistics of previous failures. However, such an approach is both expensive due to the required frequent visits to a workshop and inefficient as many components from the vehicles in the fleet are still operational. A prognostic method, allowing for vehicle individualized maintenance plans, therefore poses a significant potential in the automotive field. The prognostic method estimates component degradation and remaining useful life based on recorded data and how the vehicle has been operated.

    Lead-acid batteries is a part of the electrical power system in a heavy-duty truck, primarily responsible for powering the starter motor but also powering auxiliary units, e.g., cabin heating and kitchen equipment, which makes the battery a vital component for vehicle availability. Developing physical models of battery degradation is a difficult process which requires access to battery health sensing that is not available in the given study as well a detailed knowledge of battery chemistry.

    An alternative approach, considered in this work, is data-driven methods based on large amounts of logged data describing vehicle operation conditions. In the use-case studied, recorded data is not closely related to battery health which makes battery prognostic challenging. Data is collected during infrequent and non-equidistant visits to a workshop and there are complex dependencies between variables in the data. The main aim of this work has been to develop a framework and methods for estimating lifetime of lead-acid batteries using data-driven methods for condition-based maintenance. The methodology is general and can be applicable for prognostics of other components.

    A main contribution of the thesis is development of machine learning models for predictive maintenance, estimating conditional reliability functions, using Random Survival Forests (RSF) and recurrent neural networks (RNN). An important property of the data is that for a specific vehicle there may be multiple data readouts, but also one single data readout which makes predictive modeling challenging and dealing with this situation is discussed for both RSF and neural networks models. Data quality is important when building data-driven models, and here the data is imbalanced since there are few battery failures relative to the number of vehicles. Further, the data includes many uninformative variables and among those that are informative, there are complex dependencies and correlation. Methods for selecting which data features to use in the model in this situation is also a key contribution. When a point estimation of the conditional reliability functions is available, it is of interest to know how uncertain the estimate is as it allows to take quality of the prediction into account when deciding on maintenance actions. A theory for estimating the variance of the RSF predictor is another contribution in the thesis. To conclude, the results show that Long Short-Term Memory networks, which is a type of RNN, is the most suitable for the vehicle operational data and give the best performance among methods evaluated in the thesis.

    List of papers
    1. Heavy-duty truck battery failure prognostics using random survival forests
    Open this publication in new window or tab >>Heavy-duty truck battery failure prognostics using random survival forests
    2016 (English)In: IFAC PAPERSONLINE, ELSEVIER SCIENCE BV , 2016, Vol. 49, no 11, p. 562-569Conference paper, Published paper (Refereed)
    Abstract [en]

    Predicting lead-acid battery failure is important for heavy-duty trucks to avoid unplanned stops by the road. There are large amount of data from trucks in operation, however, data is not closely related to battery health which makes battery prognostic challenging. A new method for identifying important variables for battery failure prognosis using random survival forests is proposed. Important variables are identified and the results of the proposed method are compared to existing variable selection methods. This approach is applied to generate a prognosis model for lead-acid battery failure in trucks and the results are analyzed. (C) 2016, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved.

    Place, publisher, year, edition, pages
    ELSEVIER SCIENCE BV, 2016
    Keywords
    Battery failure prognosis; Random survival forests; Variable selection
    National Category
    Transport Systems and Logistics
    Identifiers
    urn:nbn:se:liu:diva-132240 (URN)10.1016/j.ifacol.2016.08.082 (DOI)000383464400082 ()
    Conference
    8th IFAC Symposium on Advances in Automotive Control (AAC)
    Available from: 2016-10-24 Created: 2016-10-21 Last updated: 2020-01-24
    2. Variable selection for heavy-duty vehicle battery failure prognostics using random survival forests
    Open this publication in new window or tab >>Variable selection for heavy-duty vehicle battery failure prognostics using random survival forests
    2016 (English)In: PHME 2016 Proceedings of the Third European Conference of the Prognostics and Health Management Society 2016, Bilbao, Spain July 5–8, 2016 / [ed] Ioana Eballard and Anibal Bregon, 2016, p. 649-659Conference paper, Published paper (Refereed)
    Abstract [en]

    Prognostics and health management is a useful tool for more flexible maintenance planning and increased system reliability. The application in this study is lead-acid battery failure prognosis for heavy-duty trucks which is important to avoid unplanned stops by the road. There are large amounts of data available, logged from trucks in operation. However, datais not closely related to battery health which makes battery prognostic challenging. When developing a data-driven prognostics model and the number of available variables is large,variable selection is an important task, since including non-informative variables in the model have a negative impact on prognosis performance. Two features of the dataset has been identified, 1) few informative variables, and 2) highly correlated variables in the dataset. The main contribution is a novel method for identifying important variables, taking these two properties into account, using Random Survival Forests to estimate prognostics models. The result of the proposed method is compared to existing variable selection methods,and applied to a real-world automotive dataset. Prognostic models with all and reduced set of variables are generated and differences between the model predictions are discussed, and favorable properties of the proposed approach are highlighted.

    Keywords
    variable selection, random survival forest, battery failure prognostics
    National Category
    Other Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:liu:diva-131788 (URN)978-1-936263-21-9 (ISBN)
    Conference
    Third European Conference of the Prognostics and Health Management Society 2016, Bilbao, July 5-8, 2016
    Available from: 2016-10-06 Created: 2016-10-06 Last updated: 2020-01-24Bibliographically approved
    3. Data-Driven Battery Lifetime Prediction and Confidence Estimation for Heavy-Duty Trucks
    Open this publication in new window or tab >>Data-Driven Battery Lifetime Prediction and Confidence Estimation for Heavy-Duty Trucks
    2018 (English)In: IEEE Transactions on Reliability, ISSN 0018-9529, E-ISSN 1558-1721, Vol. 67, no 2, p. 623-639Article in journal (Refereed) Published
    Abstract [en]

    Maintenance planning is important in the automotive industry as it allows fleet owners or regular customers to avoid unexpected failures of the components. One cause of unplanned stops of heavy-duty trucks is failure in the lead-acid starter battery. High availability of the vehicles can be achieved by changing the battery frequently, but such an approach is expensive both due to the frequent visits to a workshop and also due to the component cost. Here, a data-driven method based on random survival forest (RSF) is proposed for predicting the reliability of the batteries. The dataset available for the study, covering more than 50 000 trucks, has two important properties. First, it does not contain measurements related directly to the battery health; second, there are no time series of measurements for every vehicle. In this paper, the RSF method is used to predict the reliability function for a particular vehicle using data from the fleet of vehicles given that only one set of measurements per vehicle is available. A theory for confidence bands for the RSF method is developed, which is an extension of an existing technique for variance estimation in the random forest method. Adding confidence bands to the RSF method gives an opportunity for an engineer to evaluate the confidence of the model prediction. Some aspects of the confidence bands are considered: their asymptotic behavior and usefulness in model selection. A problem of including time-related variables is addressed in this paper with the argument that why it is a good choice not to add them into the model. Metrics for performance evaluation are suggested, which show that the model can be used to schedule and optimize the cost of the battery replacement. The approach is illustrated extensively using the real-life truck data case study.

    Place, publisher, year, edition, pages
    IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2018
    Keywords
    Battery lifetime prognostics; data-driven prediction; flexible maintenance; infinitesimal jackknife (IJ) confidence bands; reliability
    National Category
    Other Computer and Information Science
    Identifiers
    urn:nbn:se:liu:diva-149358 (URN)10.1109/TR.2018.2803798 (DOI)000433911000015 ()
    Note

    Funding Agencies|Scania CV; FFI (Vehicle Strategic Research and Innovation)

    Available from: 2018-07-02 Created: 2018-07-02 Last updated: 2020-01-24
    4. Lead-acid battery maintenance using multilayer perceptron models
    Open this publication in new window or tab >>Lead-acid battery maintenance using multilayer perceptron models
    2018 (English)In: 2018 IEEE International Conference on Prognostics and Health Management (ICPHM), 2018, p. 1-8Conference paper, Published paper (Refereed)
    Abstract [en]

    Predictive maintenance of components has the potential to significantly reduce costs for maintenance and to reduce unexpected failures. Failure prognostics for heavy-duty truck lead-acid batteries is considered with a multilayer perceptron (MLP) predictive model. Data used in the study contains information about how approximately 46,000 vehicles have been operated starting from the delivery date until the date when they come to the workshop. The model estimates a reliability and lifetime probability function for a vehicle entering a workshop. First, this work demonstrates how heterogeneous data is handled, then the architectures of the MLP models are discussed. Main contributions are a battery maintenance planning method and predictive performance evaluation based on reliability and lifetime functions, a new model for reliability function when its true shape is unknown, the improved objective function for training MLP models, and handling of imbalanced data and comparison of performance of different neural network architectures. Evaluation shows significant improvements of the model compared to more simple, time-based maintenance plans.

    Keywords
    lead acid batteries, neural nets, preventive maintenance, reliability, lead-acid battery maintenance, MLP models, neural network architectures, reliability function, lifetime functions, predictive performance evaluation, battery maintenance planning method, heterogeneous data, lifetime probability function, multilayer perceptron predictive model, heavy-duty truck lead-acid batteries, failure prognostics, predictive maintenance, simple time-based maintenance plans, improved objective function, Batteries, Histograms, Maintenance engineering, Data models, Neural networks, Conferences
    National Category
    Transport Systems and Logistics
    Identifiers
    urn:nbn:se:liu:diva-163289 (URN)10.1109/ICPHM.2018.8448472 (DOI)
    Conference
    2018 IEEE International Conference on Prognostics and Health Management (ICPHM)
    Available from: 2020-01-24 Created: 2020-01-24 Last updated: 2020-01-24Bibliographically approved
  • Public defence: 2020-03-27 12:35 TemCAS, T-building, Linköping
    Mutter, Amelia
    Linköping University, Department of Thematic Studies, Technology and Social Change. Linköping University, Faculty of Arts and Sciences.
    Multiple Imaginaries of the Fossil Fuel Free Future: Biogas and Electricity in Swedish Urban Transport2020Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In the wake of the climate crisis, it has become increasingly evident that the fossil fuel-based transport system must undergo a global transformation. Numerous renewable fuel alternatives have been suggested, accompanied by imaginaries of how these technologies will contribute to a better future. These imaginaries have a wide-ranging impact because the implementation of each alternative technology will require the build-up of multifarious socio-technical ensembles that support their use. As a result, replacing fossil fuels with these renewable alternatives is likely to be a complex process. This dissertation considers the emergence of two such visions of renewable fuels studying imaginaries of biogas and electricity in the Swedish context. Biogas has a long history of use as a transport fuel in Sweden, where although it makes up a small percentage of total fuel use it also forms the basis of numerous municipal public transport systems. Meanwhile, electric vehicles have become increasingly attractive as more actors subscribe to an imaginary that sees the future of vehicles as shared, autonomous, and electric. This interaction is exemplified in urban public transportation as many municipalities begin to implement electric buses in an attempt to increase energy efficiency and reduce pollution. This thesis follows three case studies where the imaginaries of biogas and electric vehicles interact: urban public transport in the municipalities of Linköping and Malmö, and analysis of a comprehensive national policy document Fossil fuel freedom on the road. It contributes to a wider understanding of how visions can influence obduracy and change of transport alternatives within the wider transformation to a fossil fuel free future.  

    List of papers
    1. Mobilizing sociotechnical imaginaries of fossil-free futures - Electricity and biogas in public transport in Linkoping, Sweden
    Open this publication in new window or tab >>Mobilizing sociotechnical imaginaries of fossil-free futures - Electricity and biogas in public transport in Linkoping, Sweden
    2019 (English)In: Energy Research & Social Science, ISSN 2214-6296, E-ISSN 2214-6326, Vol. 49Article in journal (Refereed) Published
    Abstract [en]

    In response to concerns about climate change and fossil fuel reliance, Swedish national policy has set the ambitious goal of a fossil fuel independent transport fleet by 2030, opening up a widespread debate on renewable fuel choice. Across sectors and regions, this debate inspires competing visions for how this transition can be achieved. Using sociotechnical imaginaries for a theoretical background, this paper will examine two competing visions in the case of urban public transport in Linkoping, Sweden. While the biogas sociotechnical imaginary is based on the socio-material reality of the existing local infrastructure system, the electricity imaginary is gaining widespread support including from national and international interests. Using interviews with fourteen key actors and document analysis, this paper seeks to understand how local actors understand biogas and electric buses as competing technologies and how they mobilize these antagonistic imaginaries in their own visions of the future. Most often, actors mobilize both the biogas and the electric imaginary alongside each other, suggestion an attempt at reconciling them at the local level. This reconciliation sheds light on the challenge of applying national imaginaries to local cases and indicates that the complexity of multi-level systems must be considered in large scale sustainability transitions.

    Place, publisher, year, edition, pages
    ELSEVIER SCIENCE BV, 2019
    Keywords
    Sociotechnical imaginaries; Biogas; Electric vehicles; Local contexts
    National Category
    Social Sciences Interdisciplinary
    Identifiers
    urn:nbn:se:liu:diva-155537 (URN)10.1016/j.erss.2018.10.025 (DOI)000460444100001 ()
    Note

    Funding Agencies|Biogas Research Center; Linkoping University; Swedish Energy Agency

    Available from: 2019-03-27 Created: 2019-03-27 Last updated: 2020-02-03
    2. Obduracy and Change in Urban Transport: Understanding Competition Between Sustainable Fuels in Swedish Municipalities
    Open this publication in new window or tab >>Obduracy and Change in Urban Transport: Understanding Competition Between Sustainable Fuels in Swedish Municipalities
    2019 (English)In: Sustainability, ISSN 2071-1050, E-ISSN 2071-1050, SUSTAINABILITY, Vol. 11, no 21, article id 6092Article in journal (Refereed) Published
    Abstract [en]

    Within the renewable transport transition, a number of alternative technologies have emerged creating competing visions of how to reduce fossil fuel dependence. This paper examines the dynamics of competing fuels in two Swedish municipalities where electric buses have emerged, threatening incumbent biogas-based bus systems. While in Linkoping, actors are resistant to the promise of electrification, in Malmo the shift to electrify urban buses has already begun. Here, the theoretical perspectives of obduracy and sociotechnical imaginaries are used to analyze obduracy and change in Linkoping and Malmo, showing how the local contexts of these two municipalities influence obduracy or willingness to change. In Linkoping, perceived connections between the biogas-based bus system and local infrastructures of renewable waste management and organic food production cause actors to place biogas buses at the center of a sustainable future region, while in Malmo linkages to the gas network (which also distributes natural gas) cause actors to question the sustainability of the fuel in use and opens up the city to welcome new electric vehicle tests. These examples show how fuel alternatives interact with each other in the wider renewable energy transition.

    Place, publisher, year, edition, pages
    MDPI, 2019
    Keywords
    obduracy; sociotechnical imaginaries; urban public transport; electric vehicles; biogas
    National Category
    Energy Systems
    Identifiers
    urn:nbn:se:liu:diva-162889 (URN)10.3390/su11216092 (DOI)000501205200219 ()2-s2.0-85074853894 (Scopus ID)
    Note

    Funding Agencies|Swedish Energy Agency, Linkoping University

    Available from: 2020-01-02 Created: 2020-01-02 Last updated: 2020-02-03Bibliographically approved