Rail Potential Calculation: Impact of the Chosen Model on the Safety Analysis

In Traction Electrification Systems (TESs), a current flows into the rails both in normal operation and fault conditions. Therefore, in both cases, a voltage between rails and earth, called Rail Potential (RP), occurs. The international Standard EN 50122-1 requires to evaluate the RP on the basis of the voltage drop in the return circuit. In this work, this approach is named Voltage Drop Method (VDM). Usually, in this approach, the rails are considered isolated from ground, the type of interconnection between the negative pole of the converter and the grounding system of the TPS is not taken into account, and the RP in a generic point of the railway is computed multiplying the current flowing in the return path and the longitudinal resistance of the rails up to the Traction Power Substation (TPS). If the RP exceeds the maximum permissible effective touch voltages, function of time, indicated by EN 50122-1, provisions to reduce the electrocution risk shall be applied. Even if the VDM generally provides conservative values for the RP, it cannot be considered completely faithful, due to the simplifying assumptions usually adopted. Therefore, the decision process to evaluate if some measures to reduce the RP shall be adopted can lead to wrong results. In this work, a faithful circuital model of the railways was used to compute the RP for several scenarios; a comparison with the results computed by VDM was carried out. The goal is to evaluate the trustworthiness of the VDM, highlighting the differences with a more faithful model

Discriminating among the theoretical origins of new heavy Majorana neutrinos at the CERN LHC

A study on the possibility of distinguishing new heavy Majorana neutrino models at LHC energies is presented. The experimental confirmation of standard neutrinos with non-zero mass and the theoretical possibility of lepton number violation find a natural explanation when new heavy Majorana neutrinos exist. These new neutrinos appear in models with new right-handed singlets, in new doublets of some grand unified theories and left-right symmetrical models. It is expected that signals of new particles can be found at the CERN high-energy hadron collider (LHC). We present signatures and distributions that can indicate the theoretical origin of these new particles. The single and pair production of heavy Majorana neutrinos are calculated and the model dependence is discussed. Same-sign dileptons in the final state provide a clear signal for the Majorana nature of heavy neutrinos, since there is lepton number violation. Mass bounds on heavy Majorana neutrinos allowing model discrimination are estimated for three different LHC luminosities.Comment: 7 pages, 5 figure

Safe design and operation of fluidized-bed reactors: Choice between reactor models

For three different catalytic fluidized bed reactor models, two models presented by Werther and a model presented by van Deemter, the region of safe and unique operation for a chosen reaction system was investigated. Three reaction systems were used: the oxidation of benzene to maleic anhydride, the oxidation of naphthalene to phthalic anhydride, and the oxidation of ethylene to ethylene oxide. Predictions of the optimal yield, the operating temperature and the conversion were also subjects of our study. It appeared that for reactions carried out in a fluidized bed operating under conditions of good fluidization all models predicted the same region of safe and unique operation. For a well-designed fluidized bed only the constraint of uniqueness is affected by the reactor model chosen. Predictions of the yield, conversion and operating temperature appeared to fit slightly less well. But still a good indication can be obtained from any of the models since the deviation in the results was less then a few percent for all three reaction systems. The strongest deviations between the models occurs in the region of gas loads only slightly higher than the minimum fluidization velocity. As the heat transfer characteristics are bad at low gas loads this region is unsuitable for highly exothermic reactions where large amounts of heat have to be removed by the coolant. In the region of good heat transfer with gas loads at least several times higher than the minimum the three models predict the same results. For this reason we finally recommed the use of simple models

Redevelopment of an industrial case study using Event-B and Rodin

CDIS is a commercial air traffic information system that was developed using formal methods 15 years ago by Praxis, and it is still in operation today. This system is an example of an industrial scale system that has been developed using formal methods. In particular, the functional requirements of the system were specified using VVSL -- a variant of VDM. A subset of the original specification has been chosen to be reconstructed on the Rodin platform based on the new Event-B formalism. The goal of our reconstruction was to overcome three key difficulties of the original formalisation, namely the difficulty of comprehending the original specification, the lack of any mechanical proof of the consistency of the specification and the difficulty of dealing with distribution and atomicity refinement. In this paper we elucidate how a new formal notation and tool can help to overcome these difficulties