Hybrid approach for travel time seismic tomography in elliptical anysotropic media

Hybrid approach for seismic travel time tomography is proposed in the case of elliptical anisotropic media. A sequential scheme is presented that combines Simulating Annealing with Linearized Least Squares inversion: at first, Simulated Annealing is implemented to obtain a velocity model that can be used as initial guess for successive Linearized Least Square inversion; in the meantime Linear Traveltime Interpolation is diffusely used to trace raypaths and calculate traveltimes. The procedure was tested both for a synthetic model and a field study. Since the field study come from a previous study, uniquely solved by Linearized Least Squares inversion without suggestions for initial guess of the velocity model, we were interested in evaluating upgrades from hybrid approach compared with solutions coming from a single technique. We found hybrid approach able to individuate a better velocity model with respect to a ”single technique” approach but, as the improvement was slight despite of the big amount of computation time needed by simulated annealing, we had also an indirect validation of the previous results of the field study

Fact-checking of timetabling principles: a case study on the relationship between planned headways and delays

The tradeoff between reliability and level of service is a central focus for railway operators and infrastructure managers. A well-performing timetable must include an optimal level of buffer time between conflicting train movements, such that a high service delivery and a high service quality are maintained. This focus on buffer time has informed the research within the fields of timetable optimization, capacity utilization and delay propagation modeling. Despite recent and ongoing advancements in these fields, there are still disconnects between the theoretical models and their application in the design, planning and evaluation of railway timetabling. Parameters that are used in timetabling, as well as, as input to the analytical assessment models, are typically derived from practical experience and based on the macroscopic limitations of a system, rather than the microscopic conflicts inherent in its signaling system.  The objective of this paper is to support the design of fact-based timetables by introducing a method of applying statistical analysis of the relationship between planned headways and recorded delays to estimate the minimum feasible headway between conflicting train movements in a railway system. This method is applied on the busiest railway line in Denmark and the results from recorded operations are validated through microsimulation.&nbsp

Finding Common Ground For Content And Technology: A Model For Course Development

A mathematics educator and an instructional technologist developed a practical, collaborative model that integrates content and technology and applied this model to a mathematics course for prospective elementary school teachers

A Polynomial Estimate of Railway Line Delay

Railway service may be measured by the aggregate delay over a time horizon or due to an event. Timetables for railway service may dampen aggregate delay by addition of additional process time, either supplement time or buffer time. The evaluation of these variables has previously been performed by numerical analysis with simulation. This paper proposes an analytical estimate of aggregate delay with a polynomial form. The function returns the aggregate delay of a railway line resulting from an initial, primary, delay. Analysis of the function demonstrates that there should be a balance between the two remedial measures, supplement and buffer. Numerical analysis of a Copenhagen Sbane line shows that the polynomial function is valid even when theoretical assumptions are violated

Infant milk formulas: effect of storage conditions on the stability of powdered products towards autoxidation

Thirty samples of powdered infant milk formulas containing polyunsaturated fatty acids (PUFAs) have been stored at four different temperatures (20, 28, 40 and 55 °C) and periodically monitored for their malondialdehyde (MDA) content up to one year. MDA levels ranged between 250 and 350 ng/kg in sealed samples with a maximum of 566 ng/kg in samples stored at 28 °C for three weeks after opening of their original packages, previously maintained for ten months at 20 °C. Sample stored at 40° and 55 °C were also submitted to CIE (Commission Internationale de l’Eclairage) colorimetric analysis, since color is the first sensorial property that consumers may evaluate. Overall, the results demonstrated a good stability of PUFA-enriched infant milk formulas in terms of MDA content. However, some care has to be paid when these products are not promptly consumed and stored for a long time after first opening

Machine learning til realtidsforudsigelser af oprindelse-til-destination efterspørgsel for jernbaner med smart card og udbudsdata : Udvidet resumé

Realtidsforudsigelser af passagerefterspørgsel på jernbanen kan bidrage til smartere trafikstyring og på sigt til at udvikle et offentligt transportsystem som på forskellig vis imødekommer ekstraordinær efterspørgsel. Dette kræver adgang til detaljeret information om efterspørgselsmønstre i form af løbende indsamling af passagertal for hvert par af oprindelses- og destinationsstationer i korte tidsintervaller. I dette studie udvikles en machine learning model til forudsigelser af afvigelser fra det periodiske efterspørgselsmønster på Københavns S-bane i 15 minutters intervaller ved hjælp af realtidsdata fra Rejsekortet på efterspørgselssiden og Banedanmarks driftsstatistikker på udbudssiden. Studiet belyser dels betydningen af udbud for forudsigelse af efterspørgsel og dels udforskes måden hvorpå spatiotemporal data indlejres i modeller fra dyb læring for at opnå nøjagtige forudsigelser for mange-dimensionale og sparsomme data som disse