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  • Jakobsson, Erik, et al. (creator_code:aut_t)
  • Automated Usage Characterization of Mining Vehicles For Life Time Prediction
  • 2020
  • record:In_t: IFAC PAPERSONLINE. - : ELSEVIER. - 2405-8963. ; , s. 11950-11955
  • swepub:Mat_conferencepaper_t (swepub:level_refereed_t)abstract
    • The life of a vehicle is heavily influenced by how it is used, and usage information is critical to predict the future condition of the machine. In this work we present a method to categorize what task an earthmoving vehicle is performing, based on a data driven model and a single standalone accelerometer. By training a convolutional neural network using a couple of weeks of labeled data, we show that a three axis accelerometer is sufficient to correctly classify between 5 different classes with an accuracy over 96% for a balanced dataset with no manual feature generation. The results are also compared against some other machine learning techniques, showing that the convolutional neural network has the highest performance, although other techniques are not far behind. An important conclusion is that methods and ideas from the area of Human Activity Recognition (HAR) are applicable also for vehicles. Copyright (C) 2020 The Authors.
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  • Jakobsson, Erik, 1987-, et al. (creator_code:aut_t)
  • Data driven modeling and estimation of accumulated damage in mining vehicles using on-board sensors
  • 2017
  • record:In_t: PHM 2017. Proceedings of the Annual Conference of the Prognostics and Health Management Society 2017, St. Petersburg, Florida, USA, October 2–5, 2017. - : Prognostics and Health Management Society. - 9781936263264 ; , s. 98-107
  • swepub:Mat_conferencepaper_t (swepub:level_refereed_t)abstract
    • The life and condition of a MT65 mine truck frame is to a large extent related to how the machine is used. Damage from different stress cycles in the frame are accumulated over time, and measurements throughout the life of the machine are needed to monitor the condition. This results in high demands on the durability of sensors used. To make a monitoring system cheap and robust enough for a mining application, a small number of robust sensors are preferred rather than a multitude of local sensors such as strain gauges. The main question to be answered is whether a low number of robust on-board sensors can give the required information to recreate stress signals at various locations of the frame. Also the choice of sensors among many different locations and kinds are considered. A final question is whether the data could also be used to estimate road condition. By using accelerometer, gyroscope and strain gauge data from field tests of an Atlas Copco MT65 mine truck, coherence and Lasso-regression were evaluated as means to select which signals to use. ARX-models for stress estimation were created using the same data. By simulating stress signals using the models, rain flow counting and damage accumulation calculations were performed. The results showed that a low number of on-board sensors like accelerometers and gyroscopes could give enough information to recreate some of the stress signals measured. Together with a linear model, the estimated stress was accurate enough to evaluate the accumulated fatigue damage in a mining truck. The accumulated damage was also used to estimate the condition of the road on which the truck was traveling. To make a useful road monitoring system some more work is required, in particular regarding how vehicle speed influences damage accumulation.
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  • Jakobsson, Erik, et al. (creator_code:aut_t)
  • Fault Identification in Hydraulic Rock Drills from Indirect Measurement During Operation
  • 2021
  • record:In_t: IFAC PAPERSONLINE. - : ELSEVIER. - 2405-8963. ; , s. 73-78
  • swepub:Mat_conferencepaper_t (swepub:level_refereed_t)abstract
    • This work presents a method for on-line condition monitoring of a hydraulic rock drill, though some of the findings can likely be applied in other applications. A fundamental difficulty for the rock drill application is discussed, namely the similarity between frequencies of internal standing waves and rock drill operation. This results in unpredictable pressure oscillations and superposition, which makes synchronization between measurement and model difficult. To overcome this, a data driven approach is proposed. The number and types of sensors are restricted due to harsh environmental conditions, and only operational data is available. Some faults are shown to be detectable using hand-crafted engineering features, with a direct physical connection to the fault of interest. Such features are easily interpreted and are shown to be robust against disturbances. Other faults are detected by classifying measured signals against a known reference. Dynamic Time Warping is shown to be an efficient way to measure similarity for cyclic signals with stochastic elements from disturbances, wave propagation and different durations, and also for cases with very small differences in measured pressure signals. Together, the two methods enables a step towards condition monitoring of a rock drill, robustly detecting very small changes in behaviour using a minimum amount of sensors. Copyright (C) 2021 The Authors.
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  • Olsson, Mattias, 1975, et al. (creator_code:aut_t)
  • Sorption of Pu(III-IV) onto TiO2: A Preliminary Study
  • 2003
  • record:In_t: Materials Research Society Symposium Proceedings. - 155899694X ; 757, s. 517-522
  • swepub:Mat_conferencepaper_t (swepub:level_refereed_t)abstract
    • A preliminary study of the sorption of reduced plutonium (III-IV) onto TiO2 has been done under anoxic conditions at varying pH and ionic strength. The first approach was to study tetravalent Pu, but the sorption decreases with time in this case. This is probably due to disproportionation of Pu(IV) at the TiO2 surface, which then acts as a catalyst. A further observation that supports this explanation is that the sorption of Pu(IV) onto the walls of the experimental equipment is in some cases higher than the sorption of (disproportioned) Pu onto the oxide.Pu(III) sorption onto the oxide was also investigated and showed similarities with the previously investigated sorption of Pm(III) in a similar system.
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  • Sandberg, Mattias, 1982, et al. (creator_code:aut_t)
  • EU tree density limitations, socio-ecological paradoxes and farmers’ management of woody pastures in Sweden
  • 2016
  • record:In_t: World Congress Silvo-Pastoral Systems 2016 Silvo-Pastoral Systems in a changing world: functions, management and people. Portugal, Évora, 27th to 30th September 2016.
  • swepub:Mat_conferencepaper_t (swepub:level_scientificother_t)abstract
    • Silvo-pastoral systems are threatened worldwide by agricultural intensification and abandonment, leading to homogenised rural landscapes. Nevertheless, numerous lifeforms in these landscapes depend upon trees for their survival and silvo-pastoral habitats are therefore essential habitats for biodiversity conservation. Society also puts faith in multiple values of trees, ranging from climate change mitigation to socio-cultural traditions and views of the landscape. Therefore, the seemingly arbitrary and paradoxical tree density limit for pasture environments imposed by the EU through its Common Agricultural Policy (CAP) may put both biological and societal values aside. In this study, we target the effects of the CAP tree density limit on management and biodiversity of woody pastures in a low-intensively managed agricultural landscape of southern Sweden. The case of simplifying nature by using simple number limitations is used as an entry point for talking with farmers about their relationship to trees and how the management of woody pastures is influenced by policy directives. We made semi-structured, open-ended interviews with seventeen farmers and three officials working with the subsidy system and counselling. We put this in relation to previous work on biodiversity, including trees, plants and birds, in woody pastures within the same area. The interviews show that the new policy incentive shifted the management focus from grazing quality to the number of trees. The farmers are willing to cut in order to get subsidies and timber revenues, however not unreflectingly. Interesting overlaps were found between the tree species preferred by the farmers, with reference to aesthetics and traditions, and official recommendations based on biological values. Another reason for leaving trees was the care of grazing animals as they used certain tree groups as shelter. This insight further reveals the difficulties of managing the complex relations within landscapes with simplified legal measures. In the study area, woody pastures with high tree densities contribute substantially to biodiversity as species with different characteristics and tolerance/dependency of trees can co-exist in the heterogeneous environments. However, with this study we show that high biological values are not the only incentive to preserve trees in pastures. Farmers know the wide ranging social, cultural and natural values of trees, and may often themselves be as good regulators of tree management as policies intend to be. These results demonstrate a mismatch between subsidy systems, management and biodiversity of woody pastures that needs to be further scrutinised to preserve the high socio-ecological values of agricultural landscapes.
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