39 research outputs found
Oil-recovery technique selection considering Exergy and Real Option analyses
No full textGlobal energy demand is on the rise while efforts are being undertaken to increase the share of renewables to the energy mix. Even though, it is expected fossil fuels will remain an important contributor to meet this demand in the following decades. This can be attributed to the existing infrastructure, fossil fuels abundance, their energy density and ease of distribution. As of today, in the oil and gas industry, competing oil-recovery techniques are screened and evaluated with cashflow based methods such as the Net Present Value rule. This method is entirely based on economics and may neglect important aspects related to the techniques. If fossil fuels will still be produced, their contribution to climate change should be mitigated. This can be achieved by considering the efficiency of the techniques employed for extraction. Additionally, the oil and gas industry is subject to uncertainty as the oil price is volatile, as has been observed in the past few years. In order to evaluate competing techniques, it is advisable to also consider the impact of this uncertainty in their evaluation. In this thesis, the applicability of two concepts for the screening of competing oil-recovery techniques is explored. The thermodynamic efficiency is assessed with the use of Exergy analysis and the uncertainty on the price of oil is considered through the use of Real Option theory.Management of Technology (MoT
The underlying effect of public transport reliability on users’ satisfaction
No full textService reliability has an important impact on the satisfaction stated by public transport users with the service they receive. The main source of unreliability is found in headway variance, which also affects waiting times and distributes passengers unevenly across vehicles. However, it is still unclear how headway irregularity, with its impact in waiting, crowdedness and reliability, affect travellers’ service satisfaction. Different stated preference studies have identified non-linear impacts produced by overcrowding. However, none of these studies is directly related to users’ satisfaction evaluation. In this study, we investigate the existence of this non-linearity in users’ satisfaction caused by both the crowding level and the number of denied boardings through a post-service satisfaction survey of bus and metro users. An Ordered Logit Model was estimated, accounting for sample heteroscedasticity and preference heterogeneity. Overall, there is a significant and negative perception of the bus mode, keeping all other attributes equal. For users under 35 years old, comfort experienced almost always plays an important role in service satisfaction, while for those over 35 years old women are significantly more sensitive to this attribute. Most important, crowding has a negative and non-linear impact on how passengers evaluate their travel satisfaction. Using a Likert-type scale, this curve is convex. This relationship between crowding and satisfaction might bias service planning and delivery if performance indicators associated to service are not properly weighted by the number of passengers served. Improving level of service indicators in this direction might provide public transport agencies a clearer and more accurate perception of the actual users’ experience.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Transport and Plannin
Headway variability in public transport: A review of metrics, determinants, effects for quality of service and control strategies
No full textThe most relevant issues related to headway variability in public transport planning, operations and quality of service are reviewed in this paper. We discuss the causes and consequences of headway variability, the alternative metrics that have been proposed to measure it, the preventive and reactive strategies to control headway variability in both research and practice, including the role of drivers and of present and future technology, and how service provision contracts might deal with headway variability through metrics and financial incentives. The most influential elements that explain headway variability along a route are the irregularity at which vehicles are dispatched, the scheduled frequency, the distance travelled or route length, the passenger demand and associated dwell times, and the number of stops. We conclude that there is a large gap between the state-of-the-art and the state-of-practice in terms of identification of headway variability issues, as well as in the development of mitigation and control measures. It is therefore paramount that future research will contribute to closing this gap by addressing organisational, contractual and technological barriers in the implementation of measures aimed at mitigating headway variability in public transport services.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Transport and Plannin
The shareability potential of ride-pooling under alternative spatial demand patterns
No full textIn In this study, we set out to explore how various spatial patterns of travel demand drive the effectiveness of ride-pooling services. To do so, we generate a broad range of synthetic, yet plausible demand patterns. We experiment with the number of attraction centres, the dispersion of destinations around these centres, and the trip length distribution. We apply a strategic ride-pooling algorithm across the generated demand patterns to identify shareability potential using a series of metrics related to ridepooling. Our findings indicate that, under a fixed demand level, vehicle-hour reduction due to ride-pooling can range between 18 and 59%. These results depend on the concentration of travel destinations around the centre and the trip length distribution. Ride-pooling becomes more efficient when trips are longer and destinations are more concentrated. A shift from a monocentric to a polycentric demand pattern is found to have a limited impact on the prospects of ride-pooling.Transport and Plannin
An evaluation of passenger delay-based refund schemes in urban public transportation
No full textIn this thesis, the functioning of passenger delay-based refund schemes in urban public transportation settings is evaluated, such as metros or light-rails. These are used when a passenger encounters a delay on their trip, in order to grant a form of refund to them. To the best of knowledge, no research has been carried out yet on several aspects of these refund schemes, such as which design considerations can be taken into account upon establishing one, or how their performance can be evaluated. To clarify these issues, the state of the practice is reviewed by surveying the internet and the information that is being provided by the individual public transport operators. By categorising this information, it can be established what the design aspects of these refund schemes are. These are the delay type such as departure or arrival delay, the delay threshold, i.e., the minimum delay from which a trip taken is elegible for a refund, the refund type, which is the form of refund that the passenger receives, and the possibility for alternative transport to be refunded. In order to determine whether there could be a form of linearity between delays and refunds, and to facilitate the evaluation of different refund schemes, a regression analysis was carried out on approximately a year of passenger trip data and vehicle data from the Washington Metro. This enabled acquiring more reliable, i.e., excluding individual passenger’s possibly erroneous behaviour, observations of the departure delay and arrival delay of every trip taken during this study period. Using this data, a possible link between the total amounts of delays encountered and refunds granted per day was analysed. It could be concluded that there is indeed a strong linear effect between these two. Furthermore, a number of key performance indicators (KPI’s) was established which allowed to assess the performance of a set of synthetic refund schemes, in which the parameters were varied that resulted from the aforementioned survey. Furthermore, a refund scheme was recreated that uses the general punctuality on a line and subsequently refunds all travelers that can have been expected to be effected by a possible drop in this punctuality. Using these KPI’s, conclusions could be drawn on the performance of different refund schemes, in the sense of how many refunds per trip are granted, how the ratio of the average delay of all refunded trips vs. the average delay of all trips is, how many revenue losses the refund schemes yield for the operator, and how much of the time losses (using a certain Value of Time) are compensated for.Civil Engineering | Transport and Plannin
Lessons and Evaluation of a Headway Control Experiment in Washington, D.C.
No full textHeadway management can potentially reduce passenger waiting time and on-board crowding on high-frequency services. In this study, a headway control experiment was conducted and evaluated for Washington Metropolitan Area Transit Agency routes 70 and 79 in Washington, D.C. The field experiment is evaluated by performing a before–after empirical evaluation. The organizational process and challenges involved with the implementation are discussed. Overall, a reduction of 26% in passenger excess waiting time was attained, which implies annual time savings that translate into US$1 million. Even though the field experiment implementation was far from ideal, the benefits obtained so far might pave the road to a long-term commitment to shift into a fully controlled headway-based management.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Transport and Plannin
Accounting for inertia in multimodal route choice behaviour: The case of a new metro line in Santiago
No full textIf people repeat choices in daily travel behaviour under stable conditions, over time this can form habitual travel behaviour and lead to inertia. If travellers face a new metro line, to what extent does their habitual travel behaviour affect their willingness to use this new transport alternative. This study investigate the inertia effects in a multimodal public transport network using a fully revealed preference data set. Habitual route choice behaviour is quantified prior to the opening of the new metro line. We then use the quantitative metric for habitual behaviour as an indicator in the situation after the metro line opens to reflect the inertia effects of individuals. The outcome of the route discrete choice model reveal that the inertia effects for the new metro line are significant. The interaction effect of habitual travellers with the new transport alternative show that there is an additional effect for the new alternative if travellers are classified as habitual. Furthermore, not accounting for inertia effects leads to bias in travel demand estimations of the new transport alternative. The model with the inertia effect improves model fit and is able to more accurately.Transport, Infrastructure and Logistic
Antagonistic interactions safeguard mitotic propagation of genetic and epigenetic information in zebrafish
Get PDFThe stability of cellular phenotypes in developing organisms depends on error-free transmission of epigenetic and genetic information during mitosis. Methylation of cytosine residues in genomic DNA is a key epigenetic mark that modulates gene expression and prevents genome instability. Here, we report on a genetic test of the relationship between DNA replication and methylation in the context of the developing vertebrate organism instead of cell lines. Our analysis is based on the identification of hypomorphic alleles of dnmt1, encoding the DNA maintenance methylase Dnmt1, and pole1, encoding the catalytic subunit of leading-strand DNA polymerase epsilon holoenzyme (Pole). Homozygous dnmt1 mutants exhibit genome-wide DNA hypomethylation, whereas the pole1 mutation is associated with increased DNA methylation levels. In dnmt1/pole1 double-mutant zebrafish larvae, DNA methylation levels are restored to near normal values, associated with partial rescue of mutant-associated transcriptional changes and phenotypes. Hence, a balancing antagonism between DNA replication and maintenance methylation buffers against replicative errors contributing to the robustness of vertebrate development.Author correction: Lawir, DF., Soza-Ried, C., Iwanami, N. et al. Author Correction: Antagonistic interactions safeguard mitotic propagation of genetic and epigenetic information in zebrafish. Commun Biol 7, 247 (2024). DOI: 10.1038/s42003-024-05899-y</p
Integrating railway network development with hierarchically lower modalities of public transport: A case study on the Amsterdam – Lelystad corridor
No full textUrbanization, a desire for a reduction of CO2 and a need for a more efficient use of space are likely to greatly increase demand for rail travel in the coming decades. To improve railway capacity, extra infrastructure can be built, or existing track can be optimized. A silo analogy provides an interesting idea for an integral approach to network development that combines the demand of heavy-rail and bus, tram, and metro: either obtain more demand for the heavy-rail system and thus validate expensive infrastructural investments or reduce demand. Both options require a broadening of the analysis so that it includes bus, tram, and metro networks. To explore the practical implications of this analogy, the research question is set up as follows:“Does integrated public transport network development in the form of a simultaneous consideration for infrastructural investment in both heavy-rail and hierarchically lower public transport modes offer a better solution for fulfilling transportation needs, compared to a segregated approach?”To answer the research question, literature review has been used to gain insights in public transport integration from a technical and a governance perspective. Literature has also been used to form integration strategies that could be applied in network development. The formed strategies consist of using network hierarchy as a guideline for either applying bus, tram, and metro to take over lower hierarchy services from the heavy-rail and vice versa. A case study on the corridor Amsterdam – Lelystad in The Netherlands was used to apply the integration strategies on and to analyze the effects of the development following the different strategies in a real-life situation. The results show that the variant following the strategy of assigning lower hierarchy services to heavy-rail appears best in terms of generalized travel time, synthetic demand, and investment costs. It scores well on fairness of the offer, but lowest on ambition fulfillment and operational costs. It turned out that each variant needed investment in more heavy-rail infrastructure to allow for completing of the heavy-rail ambitions. The variant with more tasks assigned to bus, tram, and metro scored the worst, except for ambition fulfillment. Furthermore, the multicriteria analysis, although useful for providing insights in the qualities of the different variants, does not give a definitive answer on what the best variant would be. Using external input to assign weights to the multicriteria analyses would have been a good improvement in getting to that answer. Instead, a stakeholder reflection is done to give insight in possible stances regarding the criteria from the stakeholder’s perspective.The research suggests that it is worth considering ambitions and problems outside of just the bus, tram, and metro or just the heavy-rail system. The process of brainstorming based on expertise, using qualitative multicriteria analyses for making decisions with supporting arguments in the design phase, planning a plausible timetable and analyzing and comparing several variants forms a good skeleton for investigating the possibilities of public transport network development in places where heavy-rail capacity becomes problematic.Civil Engineering | Transport and Plannin
Tucídides Y El Camino Espartano Al Imperio
No full textScholars have long agreed on the programmatic nature of Thucydides’ archaeology (1.1-23), the author’s exposition of the defining features of Greek history before the beginning of the Atheno-Peloponnesian war. As such, the account of the ancient, first beginnings of Greece is also an analysis of the forces that long operated in Greek history and that are still evident in the great war that the author chose for his subject. Thucydides claims that the war he writes about is the greatest and most memorable of all wars, because both sides were at the full height of their power (1.1.1 y 1.21.2). He argues that the acquisition of wealth and naval supremacy were the primary routes to power in Greek history, which clearly explains, for instance, Athens’ rise to international preeminence. Sparta, however, did not follow that path at all. In fact, Thucydides never associates these changes with Sparta’s historical development. In this paper, I argue that Sparta’s unusual path to supremacy represents an alternative way to the acquisition of power, an avenue often unexplored in studies on Thucydides’ History. Although presented in a more subtle and incidental way, I seek to show that political continuity and stability over time, of which Sparta is the best example, allow, in Thucydides’ view, another viable way into imperial supremacy.Keywords: Thucydides, Sparta, imperialism, political theory, historiography.La arqueología de Tucídides (1.1-23) es a menudo considerada una declaración programática con respecto a la obra completa del autor. La narración de los comienzos de la historia griega es un análisis de las fuerzas históricas que han operado por largo tiempo en la historia de Grecia y que se manifiestan en la guerra que el autor eligió como objeto de estudio. Tucídides sostiene que la importancia de la guerra entre atenienses y espartanos radica en que ambas fuerzas en conflicto se encontraban en la cima de su poder (1.1.1 y 1.21.2). Asimismo, argumenta que el camino principal a la hegemonía es la adquisición de riquezas y la supremacía naval, lo que claramente explica, por ejemplo, el ascenso de Atenas a la primacía internacional. Sin embargo, Esparta en absoluto siguió ese camino. De hecho, Tucídides nunca asocia las dos variables anteriores con el desarrollo histórico de Lacedemonia. En este trabajo argumento que Tucídides también presenta como una vía alternativa a la adquisición de poder el camino espartano al imperio, algo a menudo inexplorado en la bibliografía sobre el tema. Más sutil y menos espectacular, aunque igualmente efectivo, la continuidad y estabilidad política en el tiempo, cuyo mejor ejemplo es Esparta, también permiten alcanzar, en la mirada de Tucídides, la supremacía imperial.Palabras clave: Tucídides, Esparta, imperialismo, teoría política, historiografía
