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- Krishna, Visakh V, et al.
(författare)
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An integrated numerical framework to investigate the running safety of overlong freight trains
- 2020
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Ingår i: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit. - : SAGE Publications. - 0954-4097 .- 2041-3017.
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Tidskriftsartikel (refereegranskat)abstract
- Long freight trains up to 1500 m in length are currently not in regular operation in Europe. One of the important reasons for the same is high inter-wagon forces generated during the operation, especially when pneumatic (P-type) brake systems are used. For long trains with multiple locomotives at different positions along the train, radio communication with necessary fail-safe mechanisms can be used to apply the brakes. Long freight train operation on a given line is subjected to various attributes such as braking/traction scenarios, loading patterns, wagon geometries, brake-block materials, buffer types, track design geometries, etc., which are referred to as heterogeneities. The complex longitudinal train dynamics arising in the train due to various heterogeneities play a major role in determining its running safety. In this context, the maximum in-train force refers to the maximum force developed between any two wagons along the train during operation. The tolerable longitudinal compressive force is the maximum compressive force that can be exerted on a wagon without resulting in its derailment. Here, the authors adopt a bottom-up approach to model pneumatic braking systems and inter-wagon interactions in multibody simulation environments to study the complex longitudinal train dynamics behavior and estimate maximum in-train forces and tolerable longitudinal compressive forces, subjected to various heterogeneities. These two force quantities intend to facilitate a given freight train operation by providing guidelines regarding the critical heterogeneities, that currently limit its safe operation. In doing so, the authors propose the notion to have an operation-based approval for long freight trains using the simulations-based tool.
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| 2. |
- Marrubini, Giorgio, et al.
(författare)
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Experimental designs for solid-phase microextraction method development in bioanalysis : A review
- 2020
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Ingår i: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 1119, s. 77-100
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Forskningsöversikt (refereegranskat)abstract
- This review is an update of a previous review in 2009 and covers publications from 2009 to 2019. The review focuses on experimental design, referred to as the design of experiments (DoE), used in developing bioanalytical solid-phase microextraction (SPME) methods. Characteristics of different SPME approaches are illustrated and critically discussed. The literature selection evidences that two-level full factorial designs, with a limited number of factors (<5), are most frequently used for preliminary factors screening. When applying the response surface methodology for the quantitative assessment of factorial effects, few quadratic models were used. The most popular were the rotatable central composite and Box-Benkhen designs. Models including more than four factors, such as fractional factorial designs (including the Plackett-Burman and Taguchi designs), were rarely used. Definitive screening and D-Optimal designs were not reported anywhere in the literature selection. When examining the diagnostic criteria used to evaluate different model's quality and validity, it was apparent the researchers relied heavily on commercial software for experimental design, analysis, and reporting of the results.
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| 3. |
- Marsilla, Maria, et al.
(författare)
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D3.2 – Safety precautions in train configuration and brake application
- 2018
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- For extensive rail freight transportation, one action to improve its capacity and efficiencyis to run long trains. From an European perspective this typically means running freight trains longer than 800-900 m. However, there are technical challenges associated with long-train operation.During traction (acceleration) the longitudinal tensile coupler forces can be significant, in particular if all locomotives are positioned in the front of the train. This might cause coupler breakage and thus loss of train integrity and safety risks.During braking (retardation) the longitudinal compressive coupler forces can become very large, especially when the braking is applied only from the front and when the braking signal is propagating slowly by the pneumatics through the main braking pipe. This issue is further emphasized when payload-dependent braking devices of the wagons do not fully match the payloads in question and when the brake blocks are of different materials. The large compressive forces may cause derailment when the train negotiates curves, in particular tight S-curves with radii such as 150 m, 170 m, etc.DYNAFREIGHT WP3 is devoted to different aspects of operation of long freight trains. In particular Task 3.1 and the present task, Task 3.2, are closely related assuming that the locomotives of the trains are not physically connected but use radio communication. It is also assumed that the traditional (P) UIC braking pneumatic system is used, thus electrically controlled pneumatic (ECP) braking is not introduced. Moreover, all couplers are assumed to consist of side buffers and central screw couplers.The work in these two DYNAFREIGHT tasks is carried out in collaboration with that of WP5 in the Shift2Rail member project Future Freight Locomotive for Europe (FFL4E). This joint work can be seen as a continuation of the work in the European project MARATHON in which some of the DYNAFREIGHT WP3 partners participated.Given the specifications defined in Task 3.1 of radio communication and traction&braking scenarios of long-train operation, the objective of Task 3.2 is to address the challenges indicated above and provide safety precautions when operating long freight trains. The Task 3.2 work rests on simulations, verified by measurements, and are split in three parts: braking pneumatics, 1D longitudinal dynamics and 3D derailment risk analysis. The pneumatics result is an important input to the 1D simulations, whose result in terms of longitudinal compressive forces (LCFs) is compared with tolerable LCFs found in the 3D analysis.In this D3.2 report Chapter 2 describes in more detail the simulation methodology adopted, the simulation tools that have been further devloped and some verifications against measurements. The first application, suggested by the FFL4E WP5 partners and consisting of an existing coal train operation with two locomotives (front+rear), is thensimulated in Chapter 3. In Chapter 4 longer and more heterogeneous freight trains are studied with the second locomotive at different positions. Some simulations have alsobeen carried out with three locomotives assuming that the second and third locomotives give identical traction/braking commands, see Chapter 4.Last but not least, Chapter 5 gives guidelines for long-train operation with respect to safety precautions in train configurations (locomotive positions, wagon types, coupler performance, brake block material, payloads), traction and braking scenarios, and tracklayout (gradients, horizontal curves).
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