1,721,029 research outputs found
Reference values for railway sidings track geometry
Full text linkRailway sidings are operated at speeds much lower than those used on national railway lines; a typical speed is 6 km/h. In establishing reference values for maintenance of railway infrastructure in terms of the geometry for such operating conditions, it is noted that both national and European regulations do not provide specific information regarding railway sidings.
The overall objective of the research is, therefore, the definition of possible reference values for track geometry, based on those adopted by European rail networks (European and national standards), which can guarantee the appropriate security level for low speed operation typical of railway sidings connected to the national network.
The basic principle in defining these values is the maximization of technical-economic efficiency and the maintenance of the acceptability of the risk associated to railway operation. The research results can therefore provide useful information about the cost-effective management of maintenance and safe operation for railway sidings.
For this purpose, the approach was inspired to that of Regulation 402/2013, which defines at European level a common safety method for risk analysis. Quantification of probabilities and damages should be based on simulation models because the available statistics do not allow significant results to be inferred. However, the research sector has not yet produced a consolidated modelling.
For these reasons, and since it is not possible to quantify probabilities reliably, the proposals resulting from this research are based on the identification of situations where it can be shown that the hazard probability remains unchanged.
The approach used to formulate possible reference values valid outside of national networks (railway sidings) is based on an understanding of the underlying principles of the codes of good practice, on the formulation of hypotheses conform to the same principles, and the proposals about mitigative measures of risk associated to the use of different reference values, such as to keep the risk of the railway within the limits of acceptability, acting conservatively so as to keep unchanged, or reduce, the probability of hazardous events.The assessment parameters, object of the first phase of the research referred to in this work and used here as an example, are longitudinal level and alignment of railway track. In the case of vehicles running at low speed, the study was conducted by varying the magnitude of the reference values by using values that belong to external intervals with respect to those in accordance with European and national codes of good practice, examining the corresponding effects on the physical quantities related to safety. The effects of their variations on the wheel-rail interaction forces were studied using a simple dynamic model (with one degree of freedom) and a random generated excitation given by track defectiveness and the corresponding random response in terms of vertical and lateral contact forces (Q and Y)
Validation of Rail Vehicle Simulations: the Importance of Wheel-Rail Friction Parameters
No full textMulti-Body System (MBS) computer modelling is frequently performed in the design-phase of railway vehicles and increasingly for virtual testing in the process of rolling stock authorisation. There is a growing necessity to improve knowledge on the effects of different modelling choices on simulation results. In this article a validation exercise is presented. The results show an unusually high tread friction coefficient and the importance of modelling the presence of lubricant on the flange for a satisfactory match between simulated and experimental results. Conclusions address the validation of MBS models, the design and virtual testing of rolling stock.Multi-Body System (MBS) computer modelling is frequently performed in the design-phase of railway vehicles and increasingly for virtual testing in the process of rolling stock authorisation. There is a growing necessity to improve knowledge on the effects of different modelling choices on simulation results. In this article a validation exercise is presented. The results show an unusually high tread friction coefficient and the importance of modelling the presence of lubricant on the flange for a satisfactory match between simulated and experimental results. Conclusions address the validation of MBS models, the design and virtual testing of rolling stock
The management of air contamination control in operating theaters: the experience of the Parma University Hospital (IT)
No full textAs part of the overall management of a Hospital, the Hygiene Unit has specific tasks including the improvement in the levels of hospital safety by air quality monitoring in hospital environments to control the sources of infection and assessing the healthiness of hospital facilities. Operating theaters (OTs) and cleanrooms air quality control can represent a focal point considering that environmental contamination depends on not only factors such as characteristics and level of maintenance of Heating, Ventilation and Air Conditioning systems (HVAC), but it also depends on the number of people present, their behavioral habits, sanitation and disinfection procedures adopted. Several studies demonstrate a high variability in microbial air contamination in different OTs with similar HVAC, suggesting the need for achieving strict control over the factors affecting air quality. The control of air contamination, as an indicator of the quality care provided, therefore sets precise objectives, accuracy from a scientific point of view including planning, analysis and interpretation of results to propose corrective actions. However, there are no generally accepted standards for sampling nor threshold values on microbial air contamination. Aerobiology skills can improve the approach to involved issues. The monitoring plan of air quality assessment at the Parma University Hospital, by the Laboratory of Aerobiology, involves approximately 80 environments equipped with turbulent or mixed air flow. This paper describes the practical approach to air contamination control of the Hospital Hygiene Department at the Parma University Hospital as an example of how Health Departments can improve safety standards for patients and operators
La normativa sulla qualità geometrica del binario e l'esercizio dei raccordi ferroviari
No full textI valori di riferimento per la manutenzione dell'infrastruttura in termini di qualità geometrica di binario previsti dalle normative nazionali ed europee non fornisco-no molte informazioni specifiche per i raccordi ferroviari. Esse appaiono conce-pite per i binari e i deviatoi delle linee principali, appartenenti alle reti nazionali interoperabili, esercite a velocità normalmente superiori a 80 km/h con rallenta-menti a velocità di 40 km/h, e quindi ben superiori a quelle di interesse per que-sto lavoro, in genere inferiori a 10 km/h. L'obiettivo generale della ricerca è per-tanto la definizione per i raccordi ferroviari di possibili valori di riferimento per la geometria del binario, e degli apparecchi di binario (deviatoi), che possano in-tegrare tali normative. I principi di base nella definizione di tali valori sono la massimizzazione dell’efficienza tecnico-economica ed il mantenimento dell'ac-cettabilità del rischio associato all'esercizio ferroviario.The reference values for infrastructure maintenance in terms of track geometric quality provided in the Italian and European regulatory documents do not supply much information specific for railway sidings. These documents appear to be conceived for tracks, switches and crossings of main lines, comprised in the in-teroperable national networks, with line speeds normally of at least 80 km/h and temporary speed restrictions usually not less than 40 km/h. Such speeds are much higher than the speeds of interest for the work described in this paper, which are most often below 10 km/h. Therefore, the general objective of the re-search is the definition of possible track-geometry reference values for sidings, including values for switches and crossings, in order to integrate the above-mentioned regulatory documents. The basic principles in the definition of such values are to maximise technical-economic efficiency and to maintain the same degree of acceptance of the risk associated to railway operations
Nuovo terminal Ro-Ro Fusina nel porto di Venezia. Analisi tecniche ed economiche per la stima della domanda di trasporto
No full textLo studio di fattibilità della previsione di crescita della domanda di trasporto di un porto è basato sulla stima della quantità di utenza nell’utilizzo di determinati sistemi di spedizione. La domanda di trasporto si correla inevitabilmente con ampi scenari di relazioni tra investimenti, trasporto e crescita sostenibile, come anche con l’utilizzo efficiente delle risorse territoriali, pubbliche e private, con la produttività e l’efficienza nell’allocazione razionale e sostenibile delle risorse finanziarie, umane e naturali. Al-tro aspetto importante riguarda l’economia dei trasporti connessa allo studio e all’ana-lisi della relazione tra il sistema di trasporto e il sistema socio-economico di riferi-mento. In particolare la valutazione della convenienza economica dei progetti di mo-bilità comporta la stima dei costi di gestione delle aziende di trasporto e la stima della domanda. Il primo obiettivo di questa indagine sul possibile sviluppo della domanda di tra-sporto del Porto di Venezia e in particolare del Terminal Ro-Ro di Fusina, è pertanto l’analisi e l’individuazione di tutti quei fattori (operatori logistici, compagnie di navi-gazione, etc), di completamento di tutte le variabili del complesso scenario. Per effet-tuare però una significativa valutazione della domanda per questa tipologia di traffico merci, caricata su navi Ro-Ro, sul piano sia economico sia infrastrutturale e previsio-nale, è stato necessario circostanziare il focus della ricerca sull’analisi dei servizi ma-rittimi di Short Sea Shipping (SSS) e sullo studio dei servizi di intermodalità ferrovia-ria dal lato terra del porto. Da qui si è poi passati all’esame approfondito dei tre aspetti fondamentali dalla cui interazione e combinazione si evince l’efficacia degli scambi intermodali. Questa costituisce il primo stadio dell’analisi dello stato dell’arte di alcuni dei principali porti italiani nei loro aspetti tecnici e logistici e nei livelli di produttività ed efficienza nell’utilizzo delle risorse economiche. I suddetti elementi risultano neces-sari per lo studio reale esplicativo della competitività del nuovo terminal di Venezia “Autostrade del mare” di Fusina, come nodo strategico per la tipologia di traffico merci effettuata con navi Ro-Ro, il cui carico, rappresentato da semirimorchi accom-pagnati e non, è poi inviato a destinazione tramite il trasporto ferroviario
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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