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  • 6601.
    Antonio, Capezza
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Andersson, Richard L.
    Ström, Valter
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Wu, Qiong
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Biocomposites.
    Sacchi, Benedetta
    Univ Milan, Dept Chem, Via Golgi 19, I-20133 Milan, Italy.
    Farris, Stefano
    Univ Milan, DeFENS, Dept Food Environm & Nutr Sci, Packaging Div, Via Celoria 2, I-20133 Milan, Italy.
    Hedenqvist, Mikael S.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Olsson, Richard T.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Preparation and Comparison of Reduced Graphene Oxide and Carbon Nanotubes as Fillers in Conductive Natural Rubber for Flexible Electronics2019In: Omega, ISSN 0030-2228, E-ISSN 1541-3764, Vol. 4, no 2Article in journal (Refereed)
    Abstract [en]

    Conductive natural rubber (NR) nanocomposites were prepared by solvent-casting suspensions of reduced graphene oxide(rGO) or carbon nanotubes (CNTs), followed by vulcanization of the rubber composites. Both rGO and CNT were compatible as fillers in the NR as well as having sufficient intrinsic electrical conductivity for functional applications. Physical (thermal) and chemical reduction of GO were investigated, and the results of the reductions were monitored by X-ray photoelectron spectroscopy for establishing a reduction protocol that was useful for the rGO nanocomposite preparation. Field-emission scanning electron microscopy showed that both nanofillers were adequately dispersed in the main NR phase. The CNT composite displays a marked mechanical hysteresis and higher elongation at break, in comparison to the rGO composites for an equal fraction of the carbon phase. Moreover, the composite conductivity was always ca. 3-4 orders of magnitude higher for the CNT composite than for the rGO composites, the former reaching a maximum conductivity of ca. 10.5 S/m, which was explained by the more favorable geometry of the CNT versus the rGO sheets. For low current density applications though, both composites achieved the necessary percolation and showed the electrical conductivity needed for being applied as flexible conductors for a light-emitting diode. 

  • 6602.
    Antonio, Capezza
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Newson, W.R.
    Olsson, R.T.
    Hedenquist, M.S:
    Johansson, E
    Advances in the use of protein-based materials: towards sustainable naturally sourced absorbent materials2019In: American Chemical Society Symposium Series (ACS), ISSN 0097-6156, E-ISSN 1947-5918, Vol. 7, no 5Article in journal (Refereed)
    Abstract [en]

    Superabsorbent polymers (SAPs) are important in the health-care and personal care industries. Products like bed pads and diapers improve the comfort and sanitary conditions for people all over the world, with SAPs reaching yearly production volumes of ca. 2 million tons. However, recent sustainability issues have questioned the high negative footprint of polymers from nonrenewable resources. Biomacromolecules, especially when functionalized, have properties that make them an attractive alternative for the production of biobased SAPs. Proteins are a particularly interesting alternative due to their high variability and because of their relatively low price, being available as side streams from the agricultural industries. Due to the harsh extraction conditions, these side stream proteins are not competing with the food industry and alternative source-effective uses are advantageous in a circular bioeconomy. As the properties of a SAP material come from a combination of neutralized functional groups to promote polar liquid uptake and intermolecular cross-links to prevent dissolution, proteins offer unique opportunities due to their variability in polymerization. An increased understanding of the protein characteristics and how these can be tuned through functionalization is therefore a prerequisite for the successful development of a commercial biobased SAP that utilizes industrial and nontoxic wastes toward more sustainable products. This review focuses on proteins as biomacromolecules with relevant characteristics for superabsorbent functions, and discusses the opportunities that they may offer toward sustainable SAPs utilizing nontoxic chemicals and following the green chemistry principles.

  • 6603.
    Antoniotti, Mattia
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Optimization of the AdBlue e vaporation module for Scania V8 engines2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The aftertreatment techniques introduced to follow the emission legislations require a constant improvement process to comply with the gradually more stringent demands. SCR is the system used nowadays to deal with NOx emissions in most heavy-duty vehicles. An aqueous-urea solution, AdBlue, is sprayed into the evaporation unit, where urea should decompose to ammonia, the reducing agent. This is a critical step because the NH3 amount available heavily affects the final nitrous oxides reduction to nitrogen. Moreover the urea decomposition’s sides reactions are likely to occur, forming deposits that increase the pressure drop and in a certain time period could even foul the system.

    The evaporation module used in the silencer for Scania trucks equipped with V8 engines consists of a pipe in pipe configuration made in stainless steel 1.4509, where the exhaust gases flow heating up the inner pipe finned on its outer surface. The AdBlue is sprayed on the inner pipe’s inner surface, creating a wall film and cooling down the tube. The production of the evaporation pipe however involves a costly manufacturing process, being made of 144 flanges laser welded on a 0.355 m length, for a total of more than 52 m of welding.

    The goal of this thesis is to analyse the heat transfer from the exhaust gases to the pipe and how to improve it, in order to achieve a lower temperature drop on the pipe due to the AdBlue dosing, reducing at the same time the risk of building up deposits. The application of different materials for the evaporation unit is also considered. Furthermore many manufacturing processes are evaluated as a cost-effective alternative to the current one.

    Although the operating points have a wide range of variation, the analysis is focused on the worst conditions for urea evaporation which are low mass flow and low flow temperature.

    Stainless steel is the best trade-off between cost, thermal conductivity and corrosion resistance but the much higher conductivity of copper alloys would justify the investigation of a copper evaporation pipe coated with stainless steel.

    Different designs of the heat flanges are assessed, first with correlations and FEA and then through a CFD analysis, where 62 different solutions are compared. The fins height results to be the most influencing parameter, requiring an increment from 7.5 mm to 11 mm to improve the heat transfer performances of the evaporation unit. The gap between each fin is also important, leading to a flanges quantity reduction suggestion. With the current fin design and half of the number of flanges, 11 mm high, the performances would improve by almost 40% (at 800 kg/h and 300℃). Furthermore both the Abstract pipe thickness and thermal conductivity are affecting the temperature drop, with different weight depending on the design and the operating point. It is however always advantageous to use a thicker wall and a material with a higher thermal conductivity.

    Lastly the tests performed on the specifically developed test rig show a good accordance with the simulations in comparing different materials but are not suitable to compare finned designs.

  • 6604. Antoniou, C
    et al.
    Balakrishna, R
    Koutsopoulos, Haris
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    A synthesis of emerging data collection technologies and their impact on traffic management applications2011In: European Transport Research Review, ISSN 1867-0717, Vol. 3, no 3, p. 139-148Article in journal (Refereed)
    Abstract [en]

    act

    Purpose: The objective of this research is to provide an overview of emerging datacollection technologies and their impact on traffic management applications. Methods: Several existing and emerging surveillance technologies are being used for traffic datacollection. Each of these technologies has different technical characteristics and operating principles, which determine the types of data collected, accuracy of the measurements, levels of maturity, feasibility and cost, and network coverage. This paper reviews the different sources of traffic surveillance data currently employed, and the types of traffic management applications they may support. Results: Automated Vehicle Identification data have several applications in traffic management and many more are certain to emerge as these data become more widely available, reliable, and accessible. Representative examples in this field are presented. Furthermore, the fusion of condition information with traffic data can result in better and more responsive dynamic trafficmanagement applications with a richer data background. Conclusions: The current state-of-the-art of traffic modeling is discussed, in the context of using emerging data sources for better planning, operations and dynamic management of road networks. 

  • 6605. Antoniou, C
    et al.
    Balakrishna, R
    Koutsopoulos, Haris
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301), Traffic and Logistics (closed 20110301).
    Emerging Data Collection Technologies and their Impact on Traffic Management Applications2008Conference paper (Refereed)
  • 6606. Antoniou, C.
    et al.
    Balakrishna, R.
    Koutsopoulos, Haris
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301), Traffic and Logistics (closed 20110301).
    Exploiting emerging data collection technologies for dynamic traffic management applications2010In: Proceedings of World Conference on Transport Research (WCTR), 2010Conference paper (Refereed)
    Abstract [en]

    Several existing and emerging surveillance technologies are being used for traffic datacollection. Each of these technologies has different technical characteristics and operatingprinciples, which determine the types of data collected, accuracy of the measurements,levels of maturity, feasibility and cost, and network coverage. This paper reviews the differentsources of traffic surveillance data currently employed, and the types of traffic managementapplications they may support. The current state-of-the-art of traffic modeling is alsodiscussed, in the context of using emerging data sources for better planning, operations anddynamic management of road networks.

  • 6607. Antoniou, C
    et al.
    Balakrishna, R
    Koutsopoulos, Haris
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Ben-Akiva, Moshe
    Calibration Methods for Simulation-Based Dynamic Traffic Assignment Systems2011In: International Journal of Modelling and Simulation, ISSN 0228-6203, Vol. 31, no 3, p. 227-233Article in journal (Refereed)
    Abstract [en]

    Dynamic Traffic Assignment (DTA) integrates complex transportation demand and network supply simulation models to estimate prevailing traffic conditions, predict future network performance and generate consistent, anticipatory route guidance. Prior to deployment, the DTA's parameters and inputs must be calibrated to accurately reflect travel behaviour and traffic dynamics. This paper presents a unified framework for off-line and on-line DTA calibration. Off-line calibration simultaneously estimates demand and supply model parameters. On-line calibration jointly updates - in real-time - the off-line estimates in order to more accurately capture current conditions. The developed methodsare flexible and can be applied to any simulation model and may utilize any availabletraffic surveillance information (including Automated Vehicle Identification systems, probe vehicles and other emerging data sources). The off-line and on-line components complement each other to efficiently combine historical and real-time information. Thecalibration approaches are demonstrated with DynaMIT (Dynamic network assignmentfor the Management of Information to Travelers), using time-varying count, speed and density data from conventional traffic sensors.

  • 6608. Antoniou, C
    et al.
    Balakrishna, R
    Koutsopoulos, Haris
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Ben-Akiva, Moshe
    Off-Line and On-Line Calibration of Dynamic Traffic Assignment Systems2009In: IFAC Proceedings Volumes, 2009, p. 104-111Conference paper (Refereed)
    Abstract [en]

    Dynamic traffic assignment (DTA) systems integrate complex transportation demand and network supply simulation models to estimate current traffic conditions, predictfuture network performance and generate consistent, anticipatory route guidance. Before they are applied, DTA system parameters and inputs must be calibrated to accurately reect travel behavior and traffic dynamics. This paper presents a systematic approach that unifies the offline and on-line calibration of DTA systems through a common framework.Off-line calibration simultaneously estimates demand and supply model parameters. The on-line calibration jointly updates in real-time the demand and supply parameter values estimated during the of-line step to better reect prevailing conditions. The methods are general and can utilize any available traffic surveillance information (including emerging data sources, such as Automated Vehicle Identification systems or probe vehicles). The two components complement each other so that the calibration of the DTAsystem parameters efficiently utilizes both historical as well as real-time information. Thecalibration approaches are demonstrated with DynaMIT (Dynamic network assignmentfor the Management of Information to Travelers), using time-varying count, speed and density data obtained from standard loop detectors.

  • 6609.
    Antoniou, C
    et al.
    MIT.
    Ben-Akiva, Moshe
    Koutsopoulos, Haris
    Northeastern University, 437 Snell Engineering Center.
    Incorporating Automated Vehicle Identification Data into Origin-Destination Estimation2004In: TRANSPORTATION NETWORK MODELING 2004, Istanbul, Turkey, 2004, p. 37-44Conference paper (Refereed)
    Abstract [en]

    A methodology for the incorporation of automated vehicle identification (AVI) data into origin-destination (O-D) estimation and prediction is presented. AVI technologies facilitate the collection of useful data, such as point-to-point travel times and subpath flows. A framework for the incorporation of AVI data into the well-established O-D estimation and prediction process is presented. Improvements are proposed for both the formulation and the inputs to the O-D estimation and prediction model. Furthermore, as the O-D estimation and prediction process is often used in the traffic estimation and prediction context, approaches to the incorporation of AVI data into other areas of the dynamic traffic assignment framework are outlined. Performance and computational issues are also considered, and the results of a case study are presented to demonstrate the approach.

  • 6610. Antoniou, C
    et al.
    Ben-Akiva, Moshe
    Koutsopoulos, Haris
    Department of Civil Engineering, North-eastern University.
    Non-Linear Kalman Filtering Algorithms for On-Line Calibration of Dynamic Traffic Assignment Models2006In: IEEE Conference on Intelligent Transportation Systems, Proceedings, ITSC, Toronto, Canada, 2006, p. 833-838Conference paper (Refereed)
    Abstract [en]

    The problem of on-line calibration of Dynamic Traffic Assignment (DTA) models is receiving increasing attention from researchers and practitioners. The problem can be formulated as a non-linear state-space model. Because of its nonlinear nature, the resulting model cannot be solved by the Kalman Filter and therefore non-linearextensions need to be considered. In this paper, three extensions to the Kalman Filteralgorithm are presented: Extended Kalman Filter (EKF), Limiting EKF (LimEKF), and Unscented Kalman Filter (UKF). The solution algorithms are applied to the calibration of the state-of-the-art DynaMIT-R DTA model and their use is demonstrated in a freeway network in Southampton, U.K. The LimEKF shows accuracy comparable to that of the bestalgorithm, but vastly superior computational performance. 

  • 6611. Antoniou, C
    et al.
    Ben-Akiva, Moshe
    Koutsopoulos, Haris
    Northeastern University, 437 Snell Engineering Center.
    Online Calibration of Dynamic Traffic Models2004In: Proceedings of the 2nd International Congress in Transport Research, 2004, p. 37-44Conference paper (Refereed)
  • 6612.
    Antoniou, C
    et al.
    MIT.
    Ben-Akiva, Moshe
    Koutsopoulos, Haris
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    On-line Calibration of Traffic Prediction Models2004In: Intelligent Transportation Systems, 2004. Proceedings. The 7th International IEEE Conference on, Washington, D.C., 2004, p. 82-87Conference paper (Refereed)
    Abstract [en]

    A methodology for the on-line calibration of the speed-density relationship is formulated as a flexible state-space model. Applicable solution approaches are discussed and three of them (extended Kalman filter (EKF), iterated EKF, and unscented Kalman filter (UKF) are selected and presented in detail. An application of the methodology with freeway sensor data from two networks in Europe and the U.S. is presented. The improvement in the estimation and prediction of speeds due to on-line calibration (compared with the speeds obtained from the off-line calibrated relationship) is demonstrated. The EKF provides the most straightforward solution to this problem, and indeed achieves considerable improvements in estimation and prediction accuracy. The benefits obtained from the -more computationally expensive-iterated EKF algorithm are shown. An innovative solution technique (the UKF) is also presented. The UKF has a number of unique qualities and advantages over the EKF, including no assumption of analytical representation of the model and no need for explicit computation of derivatives. Empirical results suggest that the UKF outperforms the other two solution techniques in prediction accuracy.

  • 6613. Antoniou, C
    et al.
    Ben-Akiva, Moshe
    Koutsopoulos, Haris
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Practical considerations for on-line calibration of traffic simulation models2011In: Proceedings of ITS2011: Intelligent Transportation Systems, 2011Conference paper (Refereed)
  • 6614. Antoniou, C.
    et al.
    Koutsopoulos, Harilaos N.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Yannis, G.
    Dynamic data-driven local traffic state estimation and prediction2013In: Transportation Research Part C: Emerging Technologies, ISSN 0968-090X, E-ISSN 1879-2359, Vol. 34, p. 89-107Article in journal (Refereed)
    Abstract [en]

    Traffic state prediction is a key problem with considerable implications in modern traffic management. Traffic flow theory has provided significant resources, including models based on traffic flow fundamentals that reflect the underlying phenomena, as well as promote their understanding. They also provide the basis for many traffic simulation models. Speed-density relationships, for example, are routinely used in mesoscopic models. In this paper, an approach for local traffic state estimation and prediction is presented, which exploits available (traffic and other) information and uses data-driven computational approaches. An advantage of the method is its flexibility in incorporating additional explanatory variables. It is also believed that the method is more appropriate for use in the context of mesoscopic traffic simulation models, in place of the traditional speed-density relationships. While these general methods and tools are pre-existing, their application into the specific problem and their integration into the proposed framework for the prediction of traffic state is new. The methodology is illustrated using two freeway data sets from Irvine, CA, and Tel Aviv, Israel. As the proposed models are shown to outperform current state-of-the-art models, they could be valuable when integrated into existing traffic estimation and prediction models.

  • 6615. Antoniou, C
    et al.
    Koutsopoulos, Haris
    Northeastern University.
    A Comparison of Machine Learning Models for Speed Estimation2006In: IFAC Proceedings Volumes, Delft, The Netherlands, 2006, p. 55-60Conference paper (Refereed)
    Abstract [en]

    Speed-density relationships are a classic way of modeling stationary traffic relationships. Besides offering valuable insight in traffic stream flows, such relationships are widely used in simulation-based Dynamic Traffic Assignment (DTA) systems. In this paper, alternative approaches for modeling traffic dynamics, appropriate for traffic simulation, are proposed. Their basic premise is the wide availability of sensor data. The approaches are based on machine learning methods such as locally weighted regression and support vector regression. Neural networks are also considered, as they are a well-established approach, successful in many applications. While such models may not provide as much insight into traffic flow theory, they allow for easy incorporation of additional information tospeed estimation, and hence, may be more appropriate for use in DTA models, especially simulation based. In particular, in this paper, it is demonstrated (using data from a network in Irvine, CA) that the use of such machine learning methods can improve the accuracy of speed estimation. 

  • 6616. Antoniou, C
    et al.
    Koutsopoulos, Haris
    Northeastern University.
    Comparison of Parametric and Non-parametric Regression Models for Speed Estimation2006Conference paper (Refereed)
  • 6617. Antoniou, C.
    et al.
    Koutsopoulos, Haris
    Northeastern University.
    Simulation-based, Real-time Traffic Flow Prediction for Congestion Pricing2007Conference paper (Refereed)
    Abstract [en]

    Traffic congestion is one of the major problems plaguing modern cities, resulting in huge productivity losses, psychological disturbance for the citizens, and adverse direct and indirect impacts to the environment. Congestion pricing is one approach that has been long considered as a promising tool for managing congestion. As the thought matures, more advanced alternatives emerge, e.g. spot pricing or dynamic congestion pricing. However, the complexity of such congestion management methods requires the ability to dynamically predict short-term traffic flows, both without any intervention but –perhaps more importantly– resulting from alternative considered congestion pricing schemes. Simulation-based, real-time traffic flow and prediction systems are appropriate for such uses, as they provide the ability to perform short-term traffic flow predictions in real-time, while explicitly modeling the response of the drivers to the proposed congestion management schemes. This paper outlines the use of traffic flow prediction systems for the development and evaluation of congestion pricing schemes.

  • 6618. Antoniou, C
    et al.
    Koutsopoulos, Haris
    Northeastern University.
    Yannis, George
    An Efficient Non-linear Kalman Filtering Algorithm Using Simultaneous Perturbation and Applications in Traffic Estimation and Prediction2007In: IEEE Conference on Intelligent Transportation Systems, Proceedings, ITSC, 2007, p. 217-222Conference paper (Refereed)
    Abstract [en]

    The Extended Kalman Filter, a well-established and straightforward extension of theKalman filter, requires a computationally intensive linearization step. In this paper, the use of the simultaneous perturbation is proposed for the computation of the gradient in a far more efficient way than the usual numerical derivatives. The resulting algorithm is applied to the problem of on-line calibration of traffic dynamics models and empirical results are presented. The use of the simultaneous perturbation gradient approximation provides significant improvement over the base case, and comparable results to those obtained by the more computationally intensive finite difference gradient approximation. 

  • 6619. Antoniou, C
    et al.
    Koutsopoulos, Haris
    Northeastern University.
    Yannis, George
    Traffic State Prediction Using Markov Chain Models2007In: Proceedings of the European Control Conference 2007, 2007, p. 2428-2435Conference paper (Refereed)
    Abstract [en]

    Motorway traffic management and control relieson models that estimate and predict traffic conditions. In thispaper, a methodology for the identification and short-termprediction of the traffic state is presented. The methodologycombines model-based clustering, variable-length Markovchains and nearest neighbor classification. An application ofthe methodology for short-term speed prediction in a freewaynetwork in Irvine, CA, shows encouraging results.

  • 6620. Antoniou, Constantinos
    et al.
    Ben-Akiva, Moshe
    Koutsopoulos, Haris N.
    Dynamic Traffic Demand Prediction Using Conventional and Emerging Data Sources2006In: IEE Proceedings Intelligent Transport Systems, ISSN 1748-0248, Vol. 153, no 1, p. 97-104Article in journal (Refereed)
    Abstract [en]

    Origin-destination (OD) flow estimation and prediction is an important problem with applications in Dynamic Traffic Management, and traffic estimation and prediction systems. Recent developments in traffic data collection technologies provide data that have not yet been used in OD estimation and prediction. In this paper, a new, flexible, and general methodology for OD estimation and prediction is presented. The methodology can incorporate any available information from conventional and emerging traffic data collection technologies (such as automatic vehicle identification systems and probe vehicles). The application of the methodology is presented through a case study. The results support the importance of incorporating additional data in the OD estimation problem. An overall improvement for estimation and one-step prediction exceeds 45 when point-to-point information is added to the model (over the base case when only point link flows are available), while an improvement of more than 35 is maintained even for four-step prediction (i.e. 1 h into the future).

  • 6621. Antoniou, Constantinos
    et al.
    Ben-Akiva, Moshe
    Koutsopoulos, Haris N.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301).
    Non–linear Kalman Filtering Algorithms for On–line Calibration of Dynamic Traffic Assignment Models2007In: IEEE transactions on intelligent transportation systems (Print), ISSN 1524-9050, E-ISSN 1558-0016, Vol. 8, no 4, p. 661-670Article in journal (Refereed)
    Abstract [en]

    An online calibration approach that jointly estimates demand and supply parameters of dynamic traffic assignment (DTA) systems is presented and empirically validated through an extensive application. The problem can be formulated as a nonlinear state-space model. Because of its nonlinear nature, the resulting model cannot be solved by the Kalman filter, and therefore, nonlinear extensions need to be considered. The following three extensions to the Kalman filtering algorithm are presented: 1) the extended Kalman filter (EKF); 2) the limiting EKF (LimEKF); and 3) the unscented Kalman filter. The solution algorithms are applied to the on-line calibration of the state-of-the-art DynaMIT DTA model, and their use is demonstrated in a freeway network in Southampton, U.K. The LimEKF shows accuracy that is comparable to that of the best algorithm but with vastly superior computational performance. The robustness of the approach to varying weather conditions is demonstrated, and practical aspects are discussed.

  • 6622. Antoniou, Constantinos
    et al.
    Ben-Akiva, Moshe
    Koutsopoulos, Haris N.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301).
    On-line Calibration of Traffic Prediction Models2005In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, Vol. 1934, p. 235-245Article in journal (Refereed)
    Abstract [en]

    A methodology for the on-line calibration of the speed-density relationship is formulated as a flexible state-space model. Applicable solution approaches are discussed and three of them (extended Kalman filter (EKF), iterated EKF, and unscented Kalman filter (UKF) are selected and presented in detail. An application of the methodology with freeway sensor data from two networks in Europe and the U.S. is presented. The improvement in the estimation and prediction of speeds due to on-line calibration (compared with the speeds obtained from the off-line calibrated relationship) is demonstrated. The EKF provides the most straightforward solution to this problem, and indeed achieves considerable improvements in estimation and prediction accuracy. The benefits obtained from the -more computationally expensive-iterated EKF algorithm are shown. An innovative solution technique (the UKF) is also presented. The UKF has a number of unique qualities and advantages over the EKF, including no assumption of analytical representation of the model and no need for explicit computation of derivatives. Empirical results suggest that the UKF outperforms the other two solution techniques in prediction accuracy.

  • 6623. Antoniou, Constantinos
    et al.
    Koutsopoulos, Haris N.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301).
    Estimation of Traffic Dynamics Models with Machine Learning Methods2006In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, Vol. 1965, p. 103-111Article in journal (Refereed)
    Abstract [en]

    Speed-density relationships are a classic way of modeling stationary traffic relationships. Besides offering valuable insight into traffic stream flows, such relationships are widely used in dynamic traffic assignment (DTA) systems. In this research, an alternative paradigm for traffic dynamics models, appropriate for traffic simulation models and based on machine-learning approaches such as k-means clustering, k-nearest-neighborhood classification, and locally weighted regression is proposed. Although these models may not provide as much insight into traffic flow theory as speed-density relationships do, they allow for easy incorporation of additional information to speed estimation and hence may be more appropriate for use in DTA models, especially simulation-based models. This paper (with data from a network in Irvine, California) demonstrates that such machine-learning methods can considerably improve the accuracy of speed estimation.

  • 6624. Antoniou, Constantinos
    et al.
    Koutsopoulos, Haris N.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Ben-Akiva, Moshe
    Chauhan, Akhilendra S.
    Evaluation of diversion strategies using dynamic traffic assignment2011In: Transportation planning and technology (Print), ISSN 0308-1060, E-ISSN 1029-0354, Vol. 34, no 3, p. 199-216Article in journal (Refereed)
    Abstract [en]

    A framework for the evaluation of the effectiveness of traffic diversion strategies for non-recurrent congestion, based on predictive guidance and using dynamic traffic assignment, is presented. Predictive guidance is based on a short-term prediction of traffic conditions, incorporating user reaction to information and guidance. A case study of the Lower Westchester County network in New York State, using DynaMIT-P, is presented to illustrate the application of the framework. DynaMIT-P is capable of evaluating diversion strategies based on predicted conditions, which take into account drivers' response to traffic information. The case study simulates the operations of predictive variable message signs positioned in strategic locations. DynaMIT-P is calibrated for the study network and used to establish base conditions for two incident scenarios in the absence of advanced traveller information systems. The effectiveness of predictive diversion strategies is evaluated (using rigorous statistical tests) by comparing traffic conditions with and without diversion strategies. The empirical findings suggest that incident diversion strategies based on predictive guidance result in travel time savings and increased travel time reliability.

  • 6625.
    Antonopoulos, Antonios
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.
    Control, Modulation and Implementation of Modular Multilevel Converters2011Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis deals with the analysis and control of the modular multilevel converter (M2C). The M2C is a promising converter technology for various high-voltage high-power applications. The reason to this is that low-distortion output quantities can be achieved with low average switching frequencies per switch and without output filters. With the M2C the output voltage has such a low harmonic content that high-power motors can be operated without any derating. However, the apparent large number of devices, requires more complex converter control techniques than a two-level counterpart. The internal control of an M2C must be designed so that the submodule capacitor voltages are equalized and stable independent of the loading conditions. An active submodule selection mechanism, included in the modulator, has been shown able to provide voltage sharing inside the converter arm. Apart from the individual capacitor voltage sharing, a strategy has to be designed to ensure that the total amount of energy stored inside the converter will always be controlled. Based on an analytical description of the converter, both feedback and open-loop control methods are suggested, simulated and experimentally evaluated, which will ensure stable operation in the whole operation range. The potential interaction of the internal controllers with an external motor current controller is also investigated. Both simulation and experimental results show that any interaction will not result in any problems neither for the converter nor for the motor control itself. A hardware implementation of a down-scaled 10 kVA three-phase laboratory prototype converter is performed, in order to evaluate the modeling and the controllers developed. The controller implementation is described in detail, as it exhibits remarkably fast response, and can be expanded up to an arbitrary number of levels. Therefore it can be used even by a full-scale converter implementation in the MW range.

  • 6626.
    Antonopoulos, Antonios
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    On the Internal Dynamics and AC-Motor Drive Application of Modular Multilevel Converters2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis is an effort to investigate the operation and the performanceof modular multilevel converters (M2Cs). Proven to be the most promisingtopology in high-voltage high-power applications, it is necessary to put aneffort in understanding the physical laws that govern the internal dynamicsof such converters, in order to design appropriate control methods. AlthoughM2Cs belong to the well-studied family of voltage-source converters (VSCs),and claim a modular structure, their control is significantly more complicatedcompared to two- or three-level VSCs, due to the fact that a much highernumber of switches and capacitors are needed in such a topology. This thesishighlights the important parameters that should be considered when designingthe control for an M2C, through analyzing its internal dynamics, and alsosuggests ways to control such converters ensuring stable operation withoutcompromising the performance of the converter.Special focus is given on ac motor-drive applications as they are very demandingand challenging for the converter performance. Interactions betweenthe internal dynamics and the dynamics of the driven motor are experimentallyinvestigated. The problem of operating the converter when connectedto a motor standing still is visited, even under the condition that a greatamount of torque and current are requested, in order to provide an idea forthe converter requirements under such conditions. Finally, an optimization ofthe converter operation is suggested in order to avoid overrating the convertercomponents in certain operation areas that this is possible.All analytical investigations presented in this thesis are confirmed by experimentalresults on a laboratory prototype converter, which was developedfor the purposes of this project. Experimental verification proves the validityof the theoretical investigations, as well as the correct performance of thecontrol methods developed during this project on a real, physical converter,hoping that the results of this thesis will be useful for large-scale implementations,in the mega- or even giga-watt power range.

  • 6627.
    Antonopoulos, Antonios
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.
    Ilves, Kalle
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.
    Ängquist, Lennart
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.
    On Interaction between Internal Converter Dynamics and Current Control of High-Performance High-Power AC Motor Drives with Modular Multilevel Converters2010In: Proc. IEEE Energy Conversion Congress and Exposition (ECCE), 2010, p. 4293-4298Conference paper (Refereed)
    Abstract [en]

    The modular multilevel converter (M2C) is a promising converter technology for various high-voltage highpower applications. The reason to this is that low-distortion output quantities can be achieved with low average switching frequencies per switch and without output filters. With the M2C the output voltage has such a low harmonic content that highpower motors can be operated without any derating. However, the apparent large number of devices, requires more complex converter control techniques than a two-level counterpart. Even though there have been several ways suggested to control the converter itself, it is still a challenge to investigate the interaction of these controllers with an external motor current controller. It is shown in the paper that the anticipated interaction will not result in any problems neither for the converter nor for the motor control itself.

  • 6628.
    Antonopoulos, Antonios
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Mörée, Gustav
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Soulard, Juliette
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Ängquist, Lennart
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Experimental evaluation of the impact of harmonics on induction motors fed by modular multilevel converters2014In: Proceedings - 2014 International Conference on Electrical Machines, ICEM 2014, 2014, p. 768-775Conference paper (Refereed)
    Abstract [en]

    Inverter-based electrical-machine drives suffer from significantly higher losses compared to sinusoidal-supply-based alternatives, fed directly from the grid. Using multilevel inverters it becomes possible to partially mitigate the effects of the switched supply waveform, while keeping the advantages of variable-speed operation. This paper aims to evaluate the increase of the losses occurring in an induction motor (IM) fed by a modular multilevel converter (M2C), when compared to grid-connected operation, in order to evaluate the impact of the inverter-generated harmonics in the machine. It is confirmed that the losses created in the motor due to the harmonic content of the inverter-generated waveforms are very low, and almost equivalent to a purely sinusoidal supply. The investigation includes an analysis of the harmonic content from experimental waveforms obtained by an 11-kW IM laboratory setup, and it is further supported by measurements of the temperature rise in the IM-stator windings. It is concluded that the M2C could create the conditions even for high-power motors to be operated without any derating.

  • 6629.
    Antonopoulos, Antonios
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.
    Siemaszko, Daniel
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.
    Ilves, Kalle
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.
    Vasiladiotis, Michail
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.
    Ängquist, Lennart
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.
    Evaluation of Control and Modulation Methods forModular Multilevel Converters2010In: Proc. Int. Power Electronics Conf. (IPEC), 2010, p. 746-753Conference paper (Refereed)
    Abstract [en]

    The modular multilevel converter is a promising converter technology for various high-voltage high-power applications. Despite the apparent simplicity of the circuit, the inherent dynamics of the converter and the balancing of the sub-module capacitor voltages impose high requirements on the control system, which can be implemented in quite different ways. To illustrate this, and to provide a guidance for future research on the subject, this paper presents an evaluation of four different control and modulation methods. The investigation is based on experiments on a down-scaled 10 kVA converter having 10 submodules per phase leg. The main items to be investigated are dynamics within the sub-modules, arm voltages and circulating currents. It is found that the suggested open-loop control method provides the fastest arm-voltage response and that the balancing approach based on a sorting algorithm is substantially faster and less complicated to implement than the method using a dedicated voltage controller for each sub-module.

     

     

  • 6630.
    Antonopoulos, Antonios
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Ängquist, Lennart
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Harnefors, Lennart
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion. ABB, Sweden.
    Ilves, Kalle
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Global Asymptotic Stability of Modular Multilevel Converters2014In: IEEE transactions on industrial electronics (1982. Print), ISSN 0278-0046, E-ISSN 1557-9948, Vol. 61, no 2, p. 603-612Article in journal (Refereed)
    Abstract [en]

    Modular multilevel converters require that the controller is designed so that the submodule capacitor voltages are equalized and stable, independent of the loading conditions. Assuming that the individual capacitor-voltage sharing is managed effectively, an open-loop strategy has been designed to ensure that the total amount of energy stored inside the converter always will be controlled. This strategy, using the steady-state solutions of the dynamic equations for controlling the total stored energy in each converter arm, has proven to be effective. The intention of this paper is to explain in a rigorous way the mechanism behind the suggested strategy and to prove that, when this open-loop strategy is used, the system becomes globally asymptotically stable. Experimental verification on a three-phase 10-kVA prototype is presented.

  • 6631.
    Antonopoulos, Antonios
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Ängquist, Lennart
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Harnefors, Lennart
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Ilves, Kalle
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Stability Analysis of Modular Multilevel Converters With Open-Loop Control2013In: 39th Annual Conference of the IEEE Industrial Electronics Society, IECON 2013, IEEE , 2013, p. 6316-6321Conference paper (Refereed)
    Abstract [en]

    Modular multilevel converters (M2Cs) require that the controller is designed so that the submodule capacitor voltages are equalized and stable, independent of the loading conditions. Provided that the individual capacitor voltage sharing is managed effectively, an open-loop strategy can been designed to ensure that the total amount of energy stored inside the converter always will be controlled. This strategy, using the steady-state solutions of the dynamic equations for controlling the total stored energy in each converter arm, has proven to be effective. The intention of this paper is to explain in a rigorous way the mechanism behind the suggested strategy, and to prove that, when this open-loop strategy is used, the system becomes globally asymptotically stable.

  • 6632.
    Antonopoulos, Antonios
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Ängquist, Lennart
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Harnefors, Lennart
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Optimal selection of the average capacitor voltage for modular multilevel converters2013In: 2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013, IEEE , 2013, p. 3368-3374Conference paper (Refereed)
    Abstract [en]

    Variable-speed drives have reduced voltage requirements when operating below the base speed. In a modular-multilevel-converter-based (M2C-based) motor drive it is then possible to operate with reduced voltage in the submodule capacitors, than at the base speed. In this sense, a greater capacitor-voltage ripple can be accommodated, without exceeding the maximum peak-capacitor voltage. This paper presents an analytical investigation for the optimal selection of the average capacitor voltage for M2Cs, when the motor is operating with rated torque, below the base speed. This method does not require any power exchange between the converter arms, so it keeps the conduction losses at the minimum level. Additionally, the method decreases the switching losses, due to the decreased capacitor-voltage level. The overall ratings of the converter remain the same as in the base-speed operation. It is shown that this method can be applied at a speed range between the base speed and down to approximately one third of it, i.e, an operating range that covers the requirements for typical pump- and fan-type applications. The results obtained from the analytical investigation are experimentally verified on a down-scaled laboratory prototype M2C.

  • 6633.
    Antonopoulos, Antonios
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Ängquist, Lennart
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Harnefors, Lennart
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Optimal Selection of the Average Capacitor Voltage for Variable-Speed Drives With Modular Multilevel Converters2015In: IEEE transactions on power electronics, ISSN 0885-8993, E-ISSN 1941-0107, Vol. 30, no 1, p. 227-234Article in journal (Refereed)
    Abstract [en]

    Variable-speed drives have reduced voltage requirementswhen operating below the base speed. In a modularmultilevel-converter-based (M2C-based) motor drive it is thenpossible to operate with reduced voltage in the submodulecapacitors, than at the base speed. In this sense, a greatercapacitor-voltage ripple can be accommodated, without exceedingthe maximum peak-capacitor voltage. This paper presents ananalytical investigation for the optimal selection of the averagecapacitor voltage for M2Cs, when the motor is operating withrated torque, below the base speed. This method does not requireany power exchange between the converter arms, so it keepsthe conduction losses at the minimum level. Additionally, themethod decreases the switching losses, due to the decreasedcapacitor-voltage level. The overall ratings of the converterremain the same as in the base-speed operation. It is shownthat this method can be applied at a speed range betweenthe base speed and down to approximately one third of it,i.e, an operating range that covers the requirements for typicalpump- and fan-type applications. The results obtained from theanalytical investigation are experimentally verified on a downscaledlaboratory prototype M2C.

  • 6634.
    Antonopoulos, Antonios
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics (closed 20110930).
    Ängquist, Lennart
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics (closed 20110930).
    Nee, Hans-Peter
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics (closed 20110930).
    On Dynamics and Voltage Control of the Modular Multilevel Converter2009In: 2009 13th European Conference on Power Electronics and Applications, EPE '09, IEEE , 2009, p. 3353-3362Conference paper (Refereed)
    Abstract [en]

    This paper discusses the impact of modulation on stability issues of the Modular Multilevel Converter (M2C). The main idea is to describe the operation of this converter system mathematically, and suggest a control method that offers stable operation in the whole operation range. A possible approach is to assume a continuous model, where all the modules in each arm are represented by variable voltage sources. and as a result, all pulse width modulation effects are disregarded. After simulating this model and testing different control methods, useful conclusions on the operation of the M2C have been extracted. The control methods are then implemented on a model with discrete half-bridge modules, in order to compare the results and to validate continuous model approach. When assuring that this model functions as expected, the goal of this paper is to conclude into a self-stabilizing voltage controller. A controller is proposed, which eliminates circulating currents between the phase legs and balances the arm voltages regardless of the imposed alteranting current.

  • 6635.
    Antonopoulos, Antonios
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Ängquist, Lennart
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Norrga, Staffan
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Ilves, Kalle
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Harnefors, Lennart
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Modular multilevel converter AC motor drives with constant torque from zero to nominal speed2014In: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 50, no 3, p. 1982-1993Article in journal (Refereed)
    Abstract [en]

    Modular multilevel converters are shown to have a great potential in the area of medium-voltage drives. Low-distortion output quantities combined with low average switching frequencies for the semiconductor devices create an ideal combination for very high-efficiency drives. However, the large number of devices and capacitors that have to conduct the fundamental-frequency current require more complex converter control techniques than its two-level counterpart. Special care needs to be taken for starting and operation at low speeds, where the low-frequency current may cause significant unbalance between the submodule capacitor voltages and disturb the output waveforms. In this paper, principles for converter operation with high torque in the whole speed range are investigated. Experimental results from a down-scaled 12-kVA prototype converter running a loaded motor at various speeds between standstill and the rated speed are also provided.

  • 6636.
    Antonopoulos, Antonios
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Ängquist, Lennart
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Norrga, Staffan
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Ilves, Kalle
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Modular multilevel converter ac motor drives with constant torque form zero to nominal speed2012In: 2012 IEEE Energy Conversion Congress and Exposition, ECCE 2012, IEEE , 2012, p. 739-746Conference paper (Refereed)
    Abstract [en]

    Modular multilevel converters (M2Cs) are shown to have a great potential in the area of medium-voltage drives. Low-distortion output quantities, combined with low average switching frequencies for the semiconductor devices create the ideal combination for very high-efficiency drives, both from an electric motor and an inverter point of view. With M2Cs the output voltage has such a low harmonic content that high-power motors can be operated without any derating. However, the large number of devices and the existence of capacitors that have to conduct the fundamental frequency current, requires more complex converter control techniques than its two-level counterpart. Special care needs to be taken under starting and operation with low frequency, where the low-frequency current may cause significant unbalance between the submodule capacitor voltages, disturb the output waveforms, and eventually cause the converter to trip. In this paper, principles for converter operation with high torque in the whole speed range, from standstill to rated speed will be investigated. The converter-control method utilizes estimation of the capacitor voltage variation, based on equations describing steady-state conditions. Experimental results from a down-scaled 12 kVA prototype converter running a loaded motor from zero up to the rated speed are provided in the paper.

  • 6637.
    Antonopoulos, Antonios
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.
    Ängquist, Lennart
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.
    Siemaszko, Daniel
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.
    Ilves, Kalle
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.
    Vasiladiotis, Michail
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.
    Inner Control of Modular Multilevel Converters - An Approach using Open-loop Estimation of Stored Energy2010In: Proc. Int. Power Electronics Conf. (IPEC), 2010, p. 1579-1585Conference paper (Refereed)
  • 6638.
    Antonopoulos, Charalampos
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology.
    Low slope roofs: Moisture transfer in inverted roofs constantly exposed to high moisture loads and drainage systems2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Low slope roofs are roofs with an inclination between 1:16 and 1:4 and have been constructed and preferred for many years due to the benefits they present. The goal of the present work is to study the following problems of low slope roofs, as they are suggested by previous relevant theses and the current needs of the market.

    1. Moisture transfer in low slope roofs with constant exposure to high levels of relative humidity. Is protection against corrosion required for steel beams placed directly under the external membranes? If yes, what kind of protection is that?
    2. Roof drainage on low slope roofs

    The study of the first subject was based on simulations of this type of structures in order to see how external moisture affects the moisture level and the potential for corrosion on steel beams. The main goal was to conclude whether we can actually build inverted roofs with steel plates or beams lying right under the roof membrane and what kind of protection is more appropriate to apply, in case it is required.

    According to the literature review conducted on roof structures, corrosion and corrosion protection, as well as the results of the simulations, the main factor defining the corrosion potential is the indoor environment. Moreover, paint coating seems to be the indicated anticorrosive protection.

    Regarding drainage, the study focused on the literature review of the current situation, the solutions applied, the existing regulations and guidelines regarding the type of systems used (full flow or gravity, internal or external), the construction of drainage valleys (inclined or horizontal) and the placement and dimensioning of drains and overflows, in order to create a short handbook with issues to be considered by the roof engineer.

    The main conclusions are that drain valleys are suggested to be constructed completely horizontal, in order to facilitate the cooperation between drains, and that full-flow systems are more efficient than gravity ones and should be preferred, as long as the roof is not exposed to solid material and prone to its accumulation around drains (e.g. roofs covered with vegetation or stone ballast, with overhanging or nearby trees).

  • 6639.
    Antonova, Rika
    et al.
    KTH, School of Computer Science and Communication (CSC), Robotics, perception and learning, RPL.
    Cruciani, Silvia
    KTH, School of Computer Science and Communication (CSC), Robotics, perception and learning, RPL.
    Smith, Christian
    KTH, School of Computer Science and Communication (CSC), Robotics, perception and learning, RPL.
    Kragic, Danica
    KTH, School of Computer Science and Communication (CSC), Robotics, perception and learning, RPL.
    Reinforcement Learning for Pivoting TaskManuscript (preprint) (Other academic)
    Abstract [en]

    In this work we propose an approach to learn a robust policy for solving the pivoting task. Recently, several model-free continuous control algorithms were shown to learn successful policies without prior knowledge of the dynamics of the task. However, obtaining successful policies required thousands to millions of training episodes, limiting the applicability of these approaches to real hardware. We developed a training procedure that allows us to use a simple custom simulator to learn policies robust to the mismatch of simulation vs robot. In our experiments, we demonstrate that the policy learned in the simulator is able to pivot the object to the desired target angle on the real robot. We also show generalization to an object with different inertia, shape, mass and friction properties than those used during training. This result is a step towards making model-free reinforcement learning available for solving robotics tasks via pre-training in simulators that offer only an imprecise match to the real-world dynamics.

  • 6640.
    Antonova, Rika
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Robotics, perception and learning, RPL.
    Kokic, Mia
    KTH, School of Electrical Engineering and Computer Science (EECS), Robotics, perception and learning, RPL.
    Stork, Johannes A.
    KTH, School of Electrical Engineering and Computer Science (EECS), Robotics, perception and learning, RPL.
    Kragic, Danica
    KTH, School of Electrical Engineering and Computer Science (EECS), Robotics, perception and learning, RPL.
    Global Search with Bernoulli Alternation Kernel for Task-oriented Grasping Informed by Simulation2018Conference paper (Refereed)
    Abstract [en]

    We develop an approach that benefits from large simulated datasets and takes full advantage of the limited online data that is most relevant. We propose a variant of Bayesian optimization that alternates between using informed and uninformed kernels. With this Bernoulli Alternation Kernel we ensure that discrepancies between simulation and reality do not hinder adapting robot control policies online. The proposed approach is applied to a challenging real-world problem of task-oriented grasping with novel objects. Our further contribution is a neural network architecture and training pipeline that use experience from grasping objects in simulation to learn grasp stability scores. We learn task scores from a labeled dataset with a convolutional network, which is used to construct an informed kernel for our variant of Bayesian optimization. Experiments on an ABB Yumi robot with real sensor data demonstrate success of our approach, despite the challenge of fulfilling task requirements and high uncertainty over physical properties of objects.

  • 6641.
    Antonova, Rika
    et al.
    KTH, School of Computer Science and Communication (CSC), Robotics, perception and learning, RPL.
    Rai, Akshara
    Robotics Institute, School of Computer Science, Carnegie Mellon University, USA.
    Atkeson, Christopher G.
    Robotics Institute, School of Computer Science, Carnegie Mellon University, USA.
    Deep kernels for optimizing locomotion controllers2017In: Proceedings of the 1st Annual Conference on Robot Learning, PMLR , 2017Conference paper (Refereed)
    Abstract [en]

    Sample efciency is important when optimizing parameters of locomotion controllers, since hardware experiments are time consuming and expensive. Bayesian Optimization, a sample-efcient optimization framework, has recently been widely applied to address this problem, but further improvements in sample efciency are needed for practical applicability to real-world robots and highdimensional controllers. To address this, prior work has proposed using domain expertise for constructing custom distance metrics for locomotion. In this work we show how to learn such a distance metric automatically. We use a neural network to learn an informed distance metric from data obtained in high-delity simulations. We conduct experiments on two different controllers and robot architectures. First, we demonstrate improvement in sample efciency when optimizing a 5-dimensional controller on the ATRIAS robot hardware. We then conduct simulation experiments to optimize a 16-dimensional controller for a 7-link robot model and obtain signicant improvements even when optimizing in perturbed environments. This demonstrates that our approach is able to enhance sample efciency for two different controllers, hence is a tting candidate for further experiments on hardware in the future. Keywor

  • 6642.
    Antonova, Rika
    et al.
    Robotics Institute, School of Computer Science, Carnegie Mellon University, USA.
    Rai, Akshara
    Robotics Institute, School of Computer Science, Carnegie Mellon University, USA.
    Atkeson, Christopher G.
    Robotics Institute, School of Computer Science, Carnegie Mellon University, USA.
    Sample efficient optimization for learning controllers for bipedal locomotion2016In: IEEE-RAS 16th International Conference on Humanoid Robots (Humanoids), 2016, IEEE conference proceedings, 2016Conference paper (Refereed)
    Abstract [en]

    Learning policies for bipedal locomotion can be difficult, as experiments are expensive and simulation does not usually transfer well to hardware. To counter this, we need algorithms that are sample efficient and inherently safe. Bayesian Optimization is a powerful sample-efficient tool for optimizing non-convex black-box functions. However, its performance can degrade in higher dimensions. We develop a distance metric for bipedal locomotion that enhances the sample-efficiency of Bayesian Optimization and use it to train a 16 dimensional neuromuscular model for planar walking. This distance metric reflects some basic gait features of healthy walking and helps us quickly eliminate a majority of unstable controllers. With our approach we can learn policies for walking in less than 100 trials for a range of challenging settings. In simulation, we show results on two different costs and on various terrains including rough ground and ramps, sloping upwards and downwards. We also perturb our models with unknown inertial disturbances analogous with differences between simulation and hardware. These results are promising, as they indicate that this method can potentially be used to learn control policies on hardware.

  • 6643.
    Antonsen, Egil
    KTH, School of Electrical Engineering (EES), Industrial Information and Control Systems.
    ORGANIZATIONAL ANTECEDENTS FOR INFORMATION SECURITY KNOWLEDGE TRANSFER2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The importance of information Security Knowledge Transfer in general, and specifically information security awareness training for overall security in organizations, makes factors benefitting information security knowledge transfer processes in the organization an important area for study. This has previously been explored in case studies but not tested in a quantitative way. This thesis investigates how Security Knowledge Transfer is affected by the factors of Organizational Structure, Business-based Information Security and Information Security Processes. After initial analysis, the Information Security Processes construct was divided into three different constructs: Performance Monitoring, Risk Assessment and Holistic Structure of Information Security. Holistic Structure of Information Security is a state in which structures with the purpose of coordinating information security across the organization exist. Both Holistic Structure of Information Security and Performance Monitoring were shown to have positive effects on Security Knowledge Transfer, however, Holistic Structure of Information Security had a relatively large effect, while Performance Monitoring had a relatively small effect. The effect of Holistic Structure of Information Security is due to that knowledge transfer in general is enabled by organizational structures. Performance Monitoring’s effect can be attributed to its property as a way to signal the importance of information security from top management to the rest of the organization and therefore act to motivate Security Knowledge Transfer among organizational members.  That two hypotheses were not supported means that two of the constructs have no direct effect on Security Knowledge Transfer. This is probably due to that one or more of the constructs that were shown to directly affect Security Knowledge Transfer mediates the effect of these constructs. To test this is left for further research.

  • 6644.
    Antonsson, Ann-Beth
    et al.
    KTH, School of Technology and Health (STH), Ergonomics (Closed 20130701).
    Christensson, Bengt
    KTH. IVL Svenska Miljöinstitutet.
    Berge, Johan
    Rättsmedicinalverket.
    Sjögren, Bengt
    Karolinska Institutet.
    Fatal Carbon Monoxide Intoxication After AcetyleneGas Welding of Pipes2013In: Annals of Occupational Hygiene, ISSN 0003-4878, E-ISSN 1475-3162, Vol. 57, no 5, p. 662-666Article in journal (Refereed)
    Abstract [en]

    Acetylene gas welding of district heating pipes can result in exposure to high concentrations of carbon monoxide. A fatal case due to intoxication is described. Measurements of carbon monoxide revealed high levels when gas welding a pipe with closed ends. This fatality and these measurements highlight a new hazard, which must be promptly prevented.

  • 6645.
    Antonsson, Hans
    et al.
    Swedish National Road and Transport Research Institute.
    Finnveden, Göran
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Environmental Strategies Research (fms).
    Gullberg, Anders
    Beser Hugosson, Muriel
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, System Analysis and Economics.
    Höjer, Mattias
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Environmental Strategies Research (fms).
    Isaksson, Karolina
    Swedish National Road and Transport Research Institute.
    Kaijser, Arne
    Philosophy and History, KTH, School of Architecture and the Built Environment (ABE), Philosophy and History of Technology, History of Science, Technology and Environment.
    Laestadius, Staffan
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.), Sustainability and Industrial Dynamics.
    Mattsson, Lars-Göran
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Nelldal, Bo-Lennart
    KTH, School of Architecture and the Built Environment (ABE), Transport Science.
    Summerton, Jane
    Swedish National Road and Transport Research Institute.
    Åkerman, Jonas
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Environmental Strategies Research (fms).
    Nu finns chansen att riva upp beslutet om förbifarten2014In: Dagens nyheter, ISSN 1101-2447, no 2014-09-16Article in journal (Other (popular science, discussion, etc.))
  • 6646.
    Antonsson, Hans
    et al.
    Swedish National Road and Transport Research Institute.
    Finnveden, Göran
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Environmental Strategies Research (fms).
    Gullberg, Anders
    Höjer, Mattias
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Environmental Strategies Research (fms).
    Isaksson, Karolina
    Swedish National Road and Transport Research Institute.
    Kaijser, Arne
    Philosophy and History, KTH, School of Architecture and the Built Environment (ABE), Philosophy and History of Technology, History of Science, Technology and Environment.
    Laestadius, Staffan
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.), Sustainability and Industrial Dynamics.
    Mattsson, Lars-Göran
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Nelldal, Bo-Lennart
    KTH, School of Architecture and the Built Environment (ABE), Transport Science.
    Summerton, Jane
    Swedish National Road and Transport Research Institute.
    Åkerman, Jonas
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Environmental Strategies Research (fms).
    Elbilar och förnybara bränslen räcker inte.2014In: Dagens nyheter, ISSN 1101-2447Article in journal (Other (popular science, discussion, etc.))
  • 6647.
    Antonsson, Hermina
    KTH, School of Industrial Engineering and Management (ITM).
    Macroeconomic factors in Probability of Default: A study applied to a Swedish credit portfolio2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Macroeconomic conditions can impact the payment capacity of individual mortgage holders' household loans. If the clients of a bank's retail credit portfolio experience deteriorating paymentcapacity it will reflect on the probability of default of the overall portfolio. With IFRS 9, banks are expected to sophisticate their calculations of expected credit loss, demanding forward-looking estimates of probability of default by incorporation of macroeconomic forecasts. Finding what macroeconomic factors have a statistical significant relationship to the actual default frequency of a portfolio can aid banks in estimating probability of default with reference to current and forecasted macroeconomic conditions.

    This study aims to explore the relationship between macroeconomic factors and the default frequency in a Swedish retail credit portfolio. The research is based on quantitative data analysis of historical default data, complemented by implications of the macroeconomic condition on the payment capacity of households from a theoretical perspective.

    Macroeconomic factors studied are the Swedish gross domestic product, house price index, reporate and unemployment rate. The supporting data consists of default data from Nordea's Swedishretail credit portfolio. The time period covers 2008-2015 and provides basis for analysis of a timeperiod with different conditions in the macroeconomy, including effects of the 2008 financial crisis. A multiple linear regression model is used as a method to suggest the relationship between themacroeconomic factors and the default frequency. The model coefficients are estimated with calculations of Ordinary Least Squares and the significance supported by statistical test.

    Results show that gross domestic product and repo rate are statistically significant macroeconomic variables in explaining changes in the default frequency and thus probability of default of a Swedish retail credit portfolio.

  • 6648.
    Antonsson Lundberg, Ann-Beth
    KTH, School of Technology and Health (STH), Ergonomics.
    A systems analysis of a target group of enterprises: A new way forward for the dissemination of research results and sustainable technologies2006Conference paper (Other academic)
  • 6649.
    Antonsson Lundberg, Ann-Beth
    KTH, School of Technology and Health (STH), Ergonomics.
    An interactive Internet tool supporting risk management in SMEs: The Chemical Guide (KemiGuiden)2005Conference paper (Other academic)
  • 6650.
    Antonsson Lundberg, Ann-Beth
    KTH, School of Technology and Health (STH), Health Systems Engineering, Ergonomics. IVL Svenska Miljöinstitutet AB.
    Företagshälsovård2014In: Människan i arbetslivet: Teori och praktik / [ed] Eva Holmström, Kerstina Olsson, Lund: Studentlitteratur AB , 2014, 2:1, p. 199-223Chapter in book (Refereed)
130131132133134135136 6601 - 6650 of 124242
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