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Häll, C. H., Ceder, A. (., Ekström, J. & Quttineh, N.-H. (2019). Adjustments of public transit operations planning process for the use of electric buses. Journal of Intelligent Transportation Systems / Taylor & Francis, 23(3), 216-230
Open this publication in new window or tab >>Adjustments of public transit operations planning process for the use of electric buses
2019 (English)In: Journal of Intelligent Transportation Systems / Taylor & Francis, ISSN 1547-2450, E-ISSN 1547-2442, Vol. 23, no 3, p. 216-230Article in journal (Refereed) Published
Abstract [en]

This work investigates and discusses how the introduction of electric buses (EB), both battery and plug-in hybrid EB, will and should change the operations planning of a public transit system. It is shown that some changes are required in the design of a transit route network, and in the timetabling and vehicle scheduling processes. Other changes are not required, but are advisable, using this opportunity upon the introduction of EB. The work covers the main characteristics of different types of EB with a short description, including the most popular charging technologies, and it presents the generally accepted transit operations planning process. Likewise, it describes and analytically formulates new challenges that arise when introducing EB. The outcome of the analyses shows that multiple new considerations must take place. It is also shown that the different charging techniques will influence the operations planning process in different ways and to a varying extent. With overnight, quick and continuous charging, the main challenges are in the network route design step, given the possibility of altering the existing network of routes, with efficient and optimal changes of the timetabling and vehicle scheduling components. An illustrative example, based on four bus lines in Norrköping, Sweden, is formulized and introduced using three problem instances of 48, 82, and 116 bus trips. The main results exhibit the minimum number of vehicles required using different scenarios of charging stations.

Place, publisher, year, edition, pages
Taylor & Francis, 2019
National Category
Transport Systems and Logistics
Identifiers
urn:nbn:se:liu:diva-152547 (URN)10.1080/15472450.2018.1488131 (DOI)000463113800002 ()
Note

Funding agencies: Swedish Energy Agency [40377-1]

Available from: 2018-11-06 Created: 2018-11-06 Last updated: 2019-05-14
Hadera, H., Ekström, J., Sand, G., Mäntysaari, J., Harjunkoski, I. & Engell, S. (2019). Integration of production scheduling and energy-cost optimization using Mean Value Cross Decomposition. Computers and Chemical Engineering, 129, Article ID UNSP 106436.
Open this publication in new window or tab >>Integration of production scheduling and energy-cost optimization using Mean Value Cross Decomposition
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2019 (English)In: Computers and Chemical Engineering, ISSN 0098-1354, E-ISSN 1873-4375, Vol. 129, article id UNSP 106436Article in journal (Refereed) Published
Abstract [en]

The integration of the optimization of the cost of the procurement of electric energy with production planning and scheduling is increasingly considered in various industries. The traditional approach to integrate production scheduling and energy procurement in industry is production driven, i.e. the production is scheduled first, after which the energy supply optimization is performed to find the best available energy portfolio. This will usually not lead to the optimum of the overall problem. The combined scheduling and energy procurement optimization can be formulated as an integrated monolithic optimization model, but the resulting problems are very hard to solve. Moreover, solutions to the two isolated problems may be available. In this paper, we propose to use Mean Value Cross Decomposition for solving the combined problem by iterating between energy-aware production scheduling and energy-cost optimization, possibly building on existing solutions. We apply the approach to two industrial use cases: a pulping process and a steel production process. MILP-based models are employed for the two scheduling problems and for the energy cost optimization a minimum-cost flow network model is used. Good quality solutions can be obtained within reasonable computation times for the two use cases.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Scheduling, Energy optimization, Demand-side management, Mean value cross decomposition
National Category
Energy Engineering
Identifiers
urn:nbn:se:liu:diva-157146 (URN)10.1016/j.compchemeng.2019.05.002 (DOI)000482588500010 ()
Note

When the article was available onlie the title of the article was wrongly stated as "nIntegration of production scheduling and energy-cost optimization using Mean Value Cross Decomposition". A correction has been sent to the journal by the authors.

Funding agencies: Marie Curie FP7-ITN project "Energy savings from smart operation of electrical, process and mechanical equipment-ENERGY-SMARTOPS [PITN-GA-2010-264940]

Available from: 2019-05-29 Created: 2019-05-29 Last updated: 2019-09-23
Grumert, E., Bernhardsson, V., Ekström, J., Gundlegård, D., Ringdahl, R. & Tapani, A. (2019). Variabla hastighetsgränser för Stockholms motorvägsnät: Effekter av alternativa algoritmer och möjligheter till styrning genom skattade trafiktillstånd. Linköping: Swedish National Road and Transport Research Institute (VTI)
Open this publication in new window or tab >>Variabla hastighetsgränser för Stockholms motorvägsnät: Effekter av alternativa algoritmer och möjligheter till styrning genom skattade trafiktillstånd
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2019 (Swedish)Report (Other academic)
Alternative title[en]
Variable speed limits for Stockholm’s urban motorways : Effects of differentalgorithms and the possibility to control by the use of estimated traffic states
Abstract [sv]

Variabla hastighetsgränser är väl utbrett på Stockholms stadsnära motorvägar och en del av Stockholms Motorway Control System (MCS). Målet med dagens system är att minska risken för olyckor och följdolyckor vid låga hastigheter, trafikstockningar m.m. Detta görs genom att mäta medelhastigheten med hjälp av fasta detektorer och uppdatera hastigheten som visas på variabla meddelandeskyltar utifrån rådande trafiktillstånd. I och med att efterfrågan på resor i Stockholm under rusningstid överstiger den tillgängliga kapaciteten i vägnätet är behovet av ett effektivt trafiksystem stort. Variabla hastighetsgränser kan bidra till ökad framkomlighet, men då dagens system har som målsättning att öka säkerheten är effekter som leder till ökad framkomlighet begränsade. Dessutom finns det i dagens system ett stort beroende av fungerande detektorer som mäter trafiktillståndet så korrekt som möjligt för att valet av hastighet ska kunna bestämmas på ett effektivt sätt.

Syftet med den här rapporten är att undersöka alternativa styralgoritmer för att bestämma variabla hastighetsgränser på Stockholms motorvägsnät. Målet är att öka framkomligheten jämfört med dagens system. Två olika sträckor med olika komplexitet, trafiksituation och problematik studeras. Valet av studerade styralgoritmer för de olika sträckorna väljs för att på bästa sätt motverka den problematiken som uppstår på de specifika sträckorna. Därmed kan val av algoritmer komma att skilja sig åt beroende på sträcka. I projektet utvärderas också om estimering av trafiktillståndet kan användas för att förbättra informationsflödet till algoritmerna då detektorer inte fungerar som de ska eller helt saknas, vilket i sin tur kan leda till förbättrad anpassning av de variabla hastighetsgränserna. Detta görs av för en av de studerade sträckorna. Styralgoritmerna utvärderas med mikroskopisk trafiksimulering och metoden utvecklad i projektet Mobile Millenium Stockholm (MMS), som bygger på en makroskopisk trafikflödesmodell och Kalman filtrering, används för estimering av trafiktillståndet.

Resultatet visar att det finns styralgoritmer med potential att öka framkomligheten. Valet av styralgoritm är dock beroende av typ av trafiksituation, vägdesignens komplexitet och trafikförhållanden på vägen. Det betyder att olika styralgoritmer kan prestera olika bra beroende på vilken vägsträcka man studerar. Vidare är estimering av trafiktillståndet användbart vid förlorad information på grund av icke-fungerande detektorer eller som komplement till detektorer för att minska mängden stationär utrustning.

Abstract [en]

Variable speed limits are commonly used on Stockholm’s urban motorways, and it is part of the Stockholm Motorway Control System (MCS). The goal of today’s system is to reduce the risk of accidents during congested conditions, traffic jams etc. This is done by updating the speed limits shown on variable message signs based on a measured average speed at fixed detectors. As the demand for travel in Stockholm during peak-hours exceeds the available capacity in the road network, the need for an efficient traffic system is high. Variable speed limit systems have the possibility to contribute to increased efficiency, but since today’s system aims to increase safety, effects that lead to increased efficiency are limited. Further, in todays’ variable speed limit systems there are a large dependency of precise and available measurements from stationary detectors to be able to display speed limits that reflects the current traffic conditions. The purpose of this report is to investigate alternative control algorithms to decide on the variable speed limits to be displayed at variable message signs on the urban motorway of Stockholm.

The goal is to increase efficiency compared to today's system. Two different road stretches with different complexity and different traffic conditions, resulting in two different types of congestion, are studied. Thereby, the studied control algorithms on the two road stretches are chosen based on the possibility of solving a specific problematic traffic situation in the best way. Hence, the studied control algorithms might differ for the two road stretches. Furthermore, for one of the roads stretches it is investigated if estimation of the traffic state can be used as input to the control algorithm as a complement to missing and erogenous measurements from stationary detectors in order to improve the calculations of the variable speed limits. The control algorithms are evaluated with microscopic traffic simulation and the method developed in the project Mobile Millenium Stockholm (MMS), using a macroscopic traffic flow model together with a Kalman filter, is used for estimation of the traffic state.

The result shows that there are control algorithms with the potential to increase efficiency. However, the choice of suitable control algorithm for improving traffic efficiency is dependent on the traffic situation, the complexity of the road design and the traffic conditions. Furthermore, estimation of the traffic state is useful when information is lost due to malfunctioning detectors or as a complement to reduce the amount of stationary detectors.

Place, publisher, year, edition, pages
Linköping: Swedish National Road and Transport Research Institute (VTI), 2019. p. 52
Series
VTI Rapport, ISSN 0347-6030, E-ISSN 0347-6030 ; 1006
Keywords
Traffic control, variable speed limits, predictive control, microscopic traffic simulation, macroscopic traffic simulation, Trafikstyrning, variabla hastighetsgränser, prediktiv styrning, mikroskopisk trafiksimulering, makroskopisk trafiksimulering
National Category
Transport Systems and Logistics
Identifiers
urn:nbn:se:liu:diva-158028 (URN)
Available from: 2019-06-24 Created: 2019-06-24 Last updated: 2019-06-24Bibliographically approved
Ekström, J. (2018). Comparison of usage-based congestion pricing schemes. In: Proceedings Transportation Research Board 97th Annual Meeting: . Paper presented at Transportation Research Board 97th Annual Meeting, January 7-11, 2018 in Washington, D.C, USA. Washington D.C.
Open this publication in new window or tab >>Comparison of usage-based congestion pricing schemes
2018 (English)In: Proceedings Transportation Research Board 97th Annual Meeting, Washington D.C., 2018Conference paper, Published paper (Refereed)
Abstract [en]

This paper investigates how usage-based pricing can be applied in order to improve the efficiency of the transportation system. Distance-based, travel time-based and delayed-based pricing schemes are investigated, both from a one-link and network perspective. A static modeling framework is adopted, based on user-equilibrium, and a simplified emission model based on the HBEFA emission model is used. Optimal usage-based fees are calculated using a surrogate-based optimization framework, and determination of zone layout is done using k-means clustering. The results for a Stockholm region network show that already with network wide pricing a large proportion of the maximum improvement of social surplus achievable with first-best pricing, can be reached. Delay-based pricing, in which the users are charged based on the excess travel time in comparison to free flow travel times, achieves 99% of the maximum improvement, already with one single fee across the whole network. With clustering of links based on their first-best optimal fees, the benefits of both distance and travel time-based fees can significantly be improved.

Place, publisher, year, edition, pages
Washington D.C.: , 2018
Series
TRB Annual Meeting Online
National Category
Engineering and Technology Transport Systems and Logistics
Identifiers
urn:nbn:se:liu:diva-147982 (URN)
Conference
Transportation Research Board 97th Annual Meeting, January 7-11, 2018 in Washington, D.C, USA
Funder
Swedish Energy Agency, 38921-1
Available from: 2018-05-21 Created: 2018-05-21 Last updated: 2018-06-13
Quttineh, N.-H., Häll, C. H., Ekström, J. & Ceder, A. (2017). Combined Timetabling and Vehicle Scheduling for Electric Buses. In: Proceedings of the 22nd International Conference of Hong Kong Society for Transportation Studies (HKSTS), December 9-11, 2017, Hong Kong, China: . Paper presented at The 22nd International Conference of Hong Kong Society for Transportation Studies (HKSTS), December 9-11, Hong Kong, China. Hong Kong: HKSTS
Open this publication in new window or tab >>Combined Timetabling and Vehicle Scheduling for Electric Buses
2017 (English)In: Proceedings of the 22nd International Conference of Hong Kong Society for Transportation Studies (HKSTS), December 9-11, 2017, Hong Kong, China, Hong Kong: HKSTS , 2017, , p. 8Conference paper, Oral presentation only (Other academic)
Abstract [en]

In this paper we present a novel mathematical model, integrating the timetabling and vehicle schedulingproblems for electric buses. The objective is to minimize the number of buses while satisfying constraintsconcerning routing and charging, including design choices of where to install charging equipment. Weillustrate the different effects of tackling the timetabling and vehicle scheduling of electric buses as separateproblems or as a joint problem, both for fixed and variable headways. To do so, tests are performed with: (i) given timetable, i.e. solving only the vehicle scheduling problem, (ii) fixed headways for each line, (iii) variable headways. For these tests, a small case based on four bidirectional bus lines is used.

Place, publisher, year, edition, pages
Hong Kong: HKSTS, 2017. p. 8
Keywords
Electric Buses, Transit Operations Planning, Timetabling, Vehicle Scheduling, MIP modeling
National Category
Computational Mathematics Transport Systems and Logistics
Identifiers
urn:nbn:se:liu:diva-148490 (URN)
Conference
The 22nd International Conference of Hong Kong Society for Transportation Studies (HKSTS), December 9-11, Hong Kong, China
Funder
Swedish Energy Agency, 40377-1
Available from: 2018-06-12 Created: 2018-06-12 Last updated: 2018-08-30Bibliographically approved
Tsanakas, N., Ekström, J. & Olstam, J. (2017). Emission estimation based on cross-sectional traffic data. In: Prceedings of TAP 2017 22nd International Transportation and Air Pollution Conference: . Paper presented at 22nd International Transportation and Air Pollution Conference, Zürich, Switzerland, 15-16 November 2017 (pp. 1-15). EMPA
Open this publication in new window or tab >>Emission estimation based on cross-sectional traffic data
2017 (English)In: Prceedings of TAP 2017 22nd International Transportation and Air Pollution Conference, EMPA , 2017, p. 1-15Conference paper, Published paper (Refereed)
Abstract [en]

The continuous traffic growth has led to highly congested cities, with negative environmental effects, both related to air quality and climate change. According to the European Environment Agency, transportation remains a significant contributor to the total emissions of the main air pollutants, (EEA, 2016). Specifically, Nitrogen Oxides (NOx), Carbon Oxide (CO) and fine particulate matter (PM2.5) make up 32%, 23% and 8% of the total emissions, respectively. This vigorous impact of vehicular emissions to the urban environmental air quality, raises concerns over the impact of traffic on human health. Therefore, the effective implementation of emission reducing policies, such as traffic control measures or congestion pricing, becomes crucial for many European cities in order to meet the air quality standards and mitigate the human exposure to pollution. To quantify the environmental effects of these measures and demonstrate their effectiveness, a reliable estimation of pollutants concentrations through emission and dispersion modelling is needed....

Place, publisher, year, edition, pages
EMPA, 2017
National Category
Civil Engineering Transport Systems and Logistics
Identifiers
urn:nbn:se:liu:diva-147873 (URN)
Conference
22nd International Transportation and Air Pollution Conference, Zürich, Switzerland, 15-16 November 2017
Projects
Förbättrad prognos av energianvändning och emissioner vid styrmedelsanalys i vägtrafiken
Funder
Swedish Energy Agency, 38921-1
Available from: 2018-05-17 Created: 2018-05-17 Last updated: 2019-05-10Bibliographically approved
Allström, A., Ekström, J., Gundlegård, D., Ringdahl, R., Rydergren, C., Bayen, A. M. & Patire, A. D. (2016). A hybrid approach for short-term traffic state and travel time prediction on highways. In: TRB 95th annual meeting compendium of papers: . Paper presented at Transportation Research Board 95th Annual Meeting, 2016-1-10 to 2016-1-14 Washington DC, United States.
Open this publication in new window or tab >>A hybrid approach for short-term traffic state and travel time prediction on highways
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2016 (English)In: TRB 95th annual meeting compendium of papers, 2016Conference paper, Published paper (Refereed)
Abstract [en]

Traffic management and traffic information are essential in urban areas, and require a good knowledge about both the current and the future traffic state. Both parametric and non-parametric traffic state prediction techniques have previously been developed, with different advantages and shortcomings. While non-parametric prediction has shown good results for predicting the traffic state during recurrent traffic conditions, parametric traffic state prediction can be used during non-recurring traffic conditions such as incidents and events. Hybrid approaches, combining the two prediction paradigms have previously been proposed by using non-parametric methods for predicting boundary conditions used in a parametric method. In this paper we instead combine parametric and non-parametric traffic state prediction techniques through assimilation in an Ensemble Kalman filter. As non-parametric prediction method a neural network method is adopted, and the parametric prediction is carried out using a cell transmission model with velocity as state. The results show that our hybrid approach can improve travel time prediction of journeys planned to commence 15 to 30 minutes into the future, using a prediction horizon of up to 50 minutes ahead in time to allow the journey to be completed.

National Category
Transport Systems and Logistics
Identifiers
urn:nbn:se:liu:diva-125386 (URN)
Conference
Transportation Research Board 95th Annual Meeting, 2016-1-10 to 2016-1-14 Washington DC, United States
Projects
Mobile Millenium Stockholm
Funder
TrenOp, Transport Research Environment with Novel Perspectives
Available from: 2016-02-22 Created: 2016-02-22 Last updated: 2016-06-03
Allström, A., Ekström, J., Gundlegård, D., Ringdahl, R., Rydergren, C., Bayen, A. M. & Patire, A. D. (2016). Hybrid Approach for Short-Term Traffic State and Travel Time Prediction on Highways. Transportation Research Record, 2554, 60-68
Open this publication in new window or tab >>Hybrid Approach for Short-Term Traffic State and Travel Time Prediction on Highways
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2016 (English)In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, Vol. 2554, p. 60-68Article in journal (Refereed) Published
Abstract [en]

Traffic management and traffic information are essential in urban areas and require reliable knowledge about the current and future traffic state. Parametric and nonparametric traffic state prediction techniques have previously been developed with different advantages and shortcomings. While nonparametric prediction has shown good results for predicting the traffic state during recurrent traffic conditions, parametric traffic state prediction can be used during nonrecurring traffic conditions, such as incidents and events. Hybrid approaches have previously been proposed; these approaches combine the two prediction paradigms by using nonparametric methods for predicting boundary conditions used in a parametric method. In this paper, parametric and nonparametric traffic state prediction techniques are instead combined through assimilation in an ensemble Kalman filter. For nonparametric prediction, a neural network method is adopted; the parametric prediction is carried out with a cell transmission model with velocity as state. The results show that the hybrid approach can improve travel time prediction of journeys planned to commence 15 to 30 min into the future, with a prediction horizon of up to 50 min ahead in time to allow the journey to be completed

Place, publisher, year, edition, pages
Washington, DC, USA: The National Academies of Sciences, Engineering, and Medicine, 2016
National Category
Transport Systems and Logistics
Identifiers
urn:nbn:se:liu:diva-132632 (URN)10.3141/2554-07 (DOI)000388911900008 ()
Funder
TrenOp, Transport Research Environment with Novel Perspectives
Note

Funding agencies: Swedish Transport Administration

Available from: 2016-11-17 Created: 2016-11-17 Last updated: 2017-11-29Bibliographically approved
Ekström, J., Kristoffersson, I. & Quttineh, N.-H. (2016). Surrogate-based optimization of cordon toll levels in congested traffic networks. Journal of Advanced Transportation, 50(6), 1008-1033
Open this publication in new window or tab >>Surrogate-based optimization of cordon toll levels in congested traffic networks
2016 (English)In: Journal of Advanced Transportation, ISSN 0197-6729, E-ISSN 2042-3195, Vol. 50, no 6, p. 1008-1033Article in journal (Refereed) Published
Abstract [en]

The benefits, in terms of social surplus, from introducing congestion pricing schemes in urban networks are depending on the design of the pricing scheme. The major part of the literature on optimal design of congestion pricing schemes is based on static traffic assignment, which is known for its deficiency in correctly predict travels in networks with severe congestion. Dynamic traffic assignment can better predict travel times in a road network, but are more computational expensive. Thus, previously developed methods for the static case cannot be applied straightforward. Surrogate-based optimization is commonly used for optimization problems with expensive-to-evaluate objective functions. In this paper we evaluate the performance of a surrogate-based optimization method, when the number of pricing schemes which we can afford to evaluate (due to the computational time) is limited to between 20 and 40. A static traffic assignment model of Stockholm is used for evaluating a large number of different configurations of the surrogatebased optimization method. Final evaluation is done with the dynamic traffic assignment tool VisumDUE, coupled with the demand model Regent, for a Stockholm network including 1 240 demand zones and 17 000 links. Our results show that the surrogate-based optimization method can indeed be used for designing a congestion pricing scheme which return a high social surplus.

Place, publisher, year, edition, pages
Wiley-Blackwell, 2016
National Category
Transport Systems and Logistics
Identifiers
urn:nbn:se:liu:diva-126894 (URN)10.1002/atr.1386 (DOI)000386040200005 ()
Available from: 2016-04-06 Created: 2016-04-06 Last updated: 2017-05-22Bibliographically approved
Hadera, H., Wide, P., Harjunkoski, I., Mäntysaari, J., Ekström, J., Sand, G. & Engell, S. (2015). A Mean Value Cross Decomposition Strategy for Demand-side Management of a Pulping Process. In: Krist V. Gernaey, Jakob K. Huusom and Gani Rafiqul (Ed.), Krist V. Gernaey; Jakob K. Huusom; Rafiqul Gani (Ed.), 2th International Symposium on Process Systems Engineering and 25th European Symposium on Computer Aided Process Engineering: . Paper presented at Joint event of the 12th International Symposium on Process Systems Engineering (PSE) and the 25th European Symposium on Computer Aided Process Engineering (ESCAPE), Copenhagen, Denmark (pp. 1931-1936). Elsevier, 37
Open this publication in new window or tab >>A Mean Value Cross Decomposition Strategy for Demand-side Management of a Pulping Process
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2015 (English)In: 2th International Symposium on Process Systems Engineering and 25th European Symposium on Computer Aided Process Engineering / [ed] Krist V. Gernaey; Jakob K. Huusom; Rafiqul Gani, Elsevier , 2015, Vol. 37, p. 1931-1936Conference paper, Published paper (Refereed)
Abstract [en]

Energy is becoming a critical resource for process industries as introduction of new policies drive changes in the energy supply systems. Energy availability and pricing is much more volatile. In this study, we propose a Mean Value Cross Decomposition approach to functionally separate production scheduling from energy-cost optimization. Such a decomposition makes it possible to exploit existing optimization solutions avoiding a need to create a new monolithic model. The proposed framework is applied to a continuous process of thermo-mechanical pulping using a discrete-time Resource-Task Network model. Example case study scenarios show that the approach gives optimal system-wide solutions while keeping the models separated.

Place, publisher, year, edition, pages
Elsevier, 2015
Series
Computer Aided Chemical Engineering, ISSN 1570-7946 ; 37
Keywords
Scheduling, demand-side management, mean value cross decomposition
National Category
Production Engineering, Human Work Science and Ergonomics
Identifiers
urn:nbn:se:liu:diva-119621 (URN)10.1016/B978-0-444-63576-1.50016-9 (DOI)000366893400016 ()978-0-444-63429-0 (ISBN)
Conference
Joint event of the 12th International Symposium on Process Systems Engineering (PSE) and the 25th European Symposium on Computer Aided Process Engineering (ESCAPE), Copenhagen, Denmark
Available from: 2015-06-23 Created: 2015-06-23 Last updated: 2019-07-15Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-1367-6793

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