Search results

Modern subway transportation systems need to satisfy increasing safety demands to rapidly evacuate passengers under hazardous emergency circumstances, such as fires, accidents or terrorist attacks, to reduce passenger injuries or life losses. The emergency evacuation capacity (EEC) of a subway station needs to be revised timely, in case passenger demand increases or the evacuation route changes in the future. However, traditional ways of estimating EEC, e.g. fire drills are time- and resource-consuming and are difficult to revise from time to time. The purpose of this study is to establish an intuitive modelling approach to increase the EEC of subway stations in a stepwised manner.

This study develops an approach to combine agent-based evacuation modelling and building information modelling (BIM) technology to estimate the total evacuation time of a subway station.

Evacuation time can be saved (33% in the studied case) from iterative improvements including stopping escalators running against the evacuation flow and modifying the geometry around escalator exits. Such iterative improvements rely on integrating agent-based modelling and BIM.

The agent-based model can provide a more realistic simulation of intelligent individual movements under emergency circumstances and provides precise feedback on locations of evacuation bottlenecks. This study also examined the effectiveness of two rounds of stepwise improvements in terms of operation or design to increase the EEC of the station.

The purpose of this paper is to present the results of the application of various models to estimate the reliability in railway repairable systems.

The methodology proposed by the International Electrotechnical Commission (IEC), using homogeneous Poisson process (HPP) and non-homogeneous Poisson process (NHPP) models, is adopted. Additionally, renewal process (RP) models, not covered by the IEC, are used, with a complementary analysis to characterize the failure intensity thereby obtained.

The findings show the impact of the recurrent failures in the times between failures (TBF) for rejection of the HPP and NHPP models. For systems not exhibiting a trend, RP models are presented, with TBF described by three-parameter lognormal or generalized logistic distributions, together with a methodology for generating clusters.

For those systems that do not exhibit a trend, TBF is assumed to be independent and identically distributed (i.i.d.), and therefore, RP models of “perfect repair” have to be used.

Maintenance managers must refocus their efforts to study the reliability of individual repairable systems and their recurrent failures, instead of collections, in order to customize maintenance to the needs of each system.

The stochastic process models were applied for the first time to electric traction systems in 23 trains and to 40 escalators with ten years of operating data in a railway company. A practical application of the IEC models is presented for the first time.

THE orthodox solution of Lagrangian frequency equations involves the expansion into polynomial form of the characteristic determinantal equation in the latent roots, but this method becomes exceedingly laborious if a large number of frequencies and their associated modes are required accurately for any system of equations of high order, say above the sixth. We define a system of Lagrangian frequency equations to be of the nth order if it consists of n equations for n homogeneous unknowns, which we call modes. A useful contribution to the problem was made by the iteration solution of Duncan and Collar, which is especially valuable when only the highest one or two latent roots are required. But when an aircraft propeller vibration problem required the first seven frequencies and their associated modes for a 12th‐order equation whose coefficients involved a variable pitch angle, the labour of calculation by this method appeared at that time (1941) to be prohibitive. The ‘Escalator’ method was therefore devised jointly by the author and Captain J. Morris of the Royal Aircraft Establishment as an alternative. In the propeller problem all the latent roots involved were necessarily real. Dr L. Fox, using relaxation methods, has recently solved a similar problem in a remarkably short time. Unfortunately, relaxation methods cannot easily be extended to the case of complex latent roots, which can occur in connexion with flutter, radio circuits and other problems. In this paper it is shown how the Escalator method can be adapted without essential change to cases in which complex quantities occur.

Why all the fuss over labeling? Certainly it is a matter of relative unimportance what we call things; the substance of the matter is far more important. When matters are put forward in this manner, this claim can hardly be denied. However, nomenclature too is important, particularly if it speaks to the essence of the categorization of an enterprise. For example, while it is undoubtedly an exaggeration to say that biology consists of nothing but naming things and categorizing them, this is not exactly so.A great deal of biological science indeed focuses on nothing other than this. It is a matter of crucial importance whether a species is part of this or the other genera, class, or phylum, for example. Also, chemistry is no different: many of its insights depend intimately on the placement of a given substance in the periodic table of elements. These are “mere” matters of nomenclature, labeling, and categorization, but they are not to be dismissed by careful scientists. A similar point can also be made in economics. In the dismal science, too, scholars speak past each other if they mean different things by such terms as “capital,” “interest,” and “profit,” etc.

The escalator process is shown to be easily applicable to certain frequency equations of Hermitian character which have been encountered in such problems as the whirling of contra propeller systems and the mechanical vibration of an aircraft.

The purpose of this paper is to explore why, despite the development of a hybrid investing logic, funding problems are so persistent for early-stage Cleantech ventures (“Cleantechs”). An institutional logics lens is adopted to analyze how key actors' perceptions and communications of the Cleantech value proposition shape information asymmetries (IAs).

A mixed methods approach draws on 82 Cleantech pitch decks and 31 investment guidance documents, and insights from interviews with 42 key informants and nine Cleantech CEOs and their investors.

IAs persist, first of all, because key investor and entrepreneurial actors combine different goals in the hybrid Cleantech value proposition. Interestingly, the analysis of Environmental Performance Indicators (EPIs) as a critical communication tool reveals a further mismatch in how actors actually combine logics. The authors ultimately identify three emergent actor roles – traditional laggard, developer and boundary spanner – that present a framework of how the three most influential actor groups develop EPIs and via that a hybrid Cleantech financing logic to overcome IAs.

The paper enhances the entrepreneurial finance literature primarily by showing that in contexts of hybrid investing a more nuanced understanding of institutional logics in terms of ends and means is critical to overcome IAs. While prior works highlight goal incompatibilities, the findings here suggest that the (in-)compatibility of goals as well as EPI choices of the same actors is likely to be the key explanandum for the stickiness of IAs and the funding gap. The novel emerging role framework offers additional theoretical, policy and practical advances for hybrid logic development.

To evacuate passengers arriving at intercity railway stations efficiently, metros and intercity railways usually share the same station or have stations close to each other. When intercity trains arrive intensively, a great number of passengers will burst into the metro station connecting with the intercity railway station within a short period, while the number of passengers will decrease substantially when intercity trains arrive sparsely. The metro timetables with regular headway currently adopted in real-world operations cannot handle the injected passenger demand properly. Timetable optimization of metro lines connecting with intercity railway stations is essential to improve service quality.

Based on arrival times of intercity trains and the entire process for passengers transferring from railway to metro, this paper develops a mathematical model to characterize the time-varying demand of passengers arriving at the platform of a metro station connecting with an intercity railway station. Provided the time-varying passenger demand and capacity of metro trains, a timetable model to optimize train departure time of a bi-direction metro line where an intermediate station connects with an intercity railway station is proposed. The objective is to minimize waiting time of passengers at the connecting station. The proposed timetable model is solved by an adaptive large neighborhood search algorithm.

Real-world case studies show that the prediction accuracy of the proposed model on passenger demand at the connecting station is higher than 90%, and the timetable model can reduce waiting time of passengers at the connecting station by 28.47% which is increased by 5% approximately than the calculation results of the generic algorithm.

This paper puts forward a model to predict the number of passengers arriving at the platform of connection stations via analyzing the entire process for passengers transferring from intercity trains to metros. Also, a timetable optimization model aiming at minimizing passenger waiting time of a metro line where an intermediate station is connected to an intercity railway station is proposed.

If an algebraic polynomial equation has roots which are negative if real and have negative real parts if complex, the coefficients must satisfy certain fundamental conditions originally formulated by Routh. These conditions are here derived by comparatively simple algebra for the sextic equation by a method which can be generalized; its extension to equations of the eighth and tenth degree is indicated. The case of damped Lagrangian frequency equations is considered as an appropriate epilogue.

Roll up, roll up … the International Online Meeting gets more like a circus every year. This year the ringmaster and some of the performers were seen covered from head to foot in stars and rosettes, making it very difficult to catch a glimpse of the most important part of the meeting — the lapel badges. You have to make sure who has changed companies, sex or name. Those expecting a new big top this year may have been disappointed to find the Novotel just a re‐vamped Cunard. However, we were promised a new improved service, no more ‘ships' museum’, no more escalator, and prime stand space upstairs. But wait, how do I get my trolley full of equipment up to this prime space? Yes, by escalator! It appeared that the easiest way to get your stand installed was by spaceship (or it may just have been the new Pergamon stand).