Darmstadt, Techn. Universiẗat, Diss., 2002. / Dateiformat: tar.gz, Dateien im PDF-Format.

München, Techn. Universiẗat, Diss., 2001.

The conflict between stability and curving has been well documented since the dawn of the railways. Advances in computer technology and deeper understanding of the complex mechanics of the wheel-rail interface have led to the study of innovative designs. This thesis outlines the need for steering systems for railway applications. A number of innovative passive solutions have been proposed to reduce the conflict between stability and curving. Comparisons of some of these solutions show that significant benefits can be obtained by using uncommon configurations.

The Gautrain Rapid Rail Link (GRRL) is a rail transit system in South Africa that links Johannesburg and Pretoria, as well as Johannesburg and the O.R. Tambo International Airport. Travelling at speeds of up to 160 km/h, the Gautrain system is the first of its kind on the African continent. This dissertation covers an investigation into the relationship between the vertical and lateral forces, speed and superelevation in a GRRL curve. The research described in this dissertation is based on an experiment which involved running a test train through a curve at various speeds, changing the cant of the curve by tamping and repeating the train runs. The cant was changed due to high wheel wear rates. The curve already had a cant deficiency, and this cant deficiency was subsequently increased by reducing the curve’s cant. Assessing the before and after tamping test data validated the existence of the expected relationships between the vertical and lateral rail forces, the speed and the cant. The change in cant had a minimal effect on the magnitude of the vertical forces, although a transfer of loading between the high and low legs did occur. The theory indicates that the 14 % reduction in cant in this curve given all of the other curve characteristics should have resulted in an increase in the lateral forces. There was however a roughly 50 % reduction in the maximum lateral forces after the cant was reduced that can be explained from a train dynamics point of view. In addition, there was an increase in safety due to a reduced derailment ratio at this curve’s normal operating speed of 85 km/h. It is not unreasonable to presume that a 50 % reduction in the maximum lateral forces could lead to a halving of the wear rate of the rail and wheels in this curve with similar results to be expected in other curves on the rail network. / Dissertation (MEng)--University of Pretoria, 2016. / The Chair in Railway Engineering at the University of Pretoria / Civil Engineering / MEng / Unrestricted

Αυτή η εργασία έχει σαν αντικείμενο την μελέτη των βαθμίδων εισόδου τελεστικών ενισχυτών με εύρος rail-to-rail καθώς και των βαθμίδων εξόδου τάξεως ΑΒ. Μια rail-to-rail βαθμίδα εισόδου, μπορεί να διαχειριστεί την τάση τροφοδοσίας στο έπακρο δεχόμενη σήματα μεγάλου εύρους τάσεων, ενώ η βαθμίδα εξόδου έχει σαν κύριο πλεονέκτημα την γρηγορότερη οδήγηση μεγάλων φορτίων με ελαχιστοποίηση της παραμόρφωσης. Έτσι, στο πρώτο κεφάλαιο παρουσιάζονται οι βασικές αρχές που διέπουν τα κυκλώματα χαμηλής τροφοδοσίας και οι περιορισμοί που πρέπει να ληφθούν υπ’ όψιν κατά τον σχεδιασμό των κυκλωμάτων. Στο δεύτερο κεφάλαιο αυτής της εργασίας παρουσιάζονται οι βασικές αρχές λειτουργίας των rail-to-rail βαθμίδων εισόδου και οι βασικές τεχνικές υλοποίησής τους. Στο τρίτο κεφάλαιο παρουσιάζονται οι βασικές αρχές λειτουργίας των βαθμίδων εξόδου τάξεως ΑΒ με τις αντίστοιχες τεχνικές υλοποίησης. Στα επόμενα κεφάλαια αυτού του συγγράμματος προτείνεται ένας νέος τελεστικός ενισχυτής ο οποίος αποτελείται από μια rail-to-rail βαθμίδα εισόδου και από μία βαθμίδα εξόδου τάξεως ΑΒ ενώ γίνεται χρήση 1V για την τάση τροφοδοσίας. Άλλο ένα πλεονέκτημα της προτεινόμενης αρχιτεκτονικής, είναι αυτό της δυνατότητας ρύθμισης των συνθηκών πόλωσης ώστε να διατηρείται η λειτουργικότητα του ενισχυτή αλλά και να προσαρμόζεται στις εκάστοτε ανάγκες της κάθε εφαρμογής. Πιο συγκεκριμένα ένα από τα πλεονεκτήματα αυτού του τελεστικού ενισχυτή, είναι η δυνατότητα ρύθμισης της διαγωγιμότητας της εισόδου με γραμμικό τρόπο μέσω μιας πηγής ρεύματος. Αντίστοιχα, επιλέγοντας μεγαλύτερο ρεύμα για την βαθμίδα εξόδου υπάρχει η δυνατότητα μείωσης της καθυστέρησης μετάδοσης του σήματος σε μεγάλα φορτία. / -

The aim of this thesis is to evaluate fatigue management systems (FMSs) within the Australian transportation industry, and provide directions for future improvement. In doing so, it draws on some preliminary data from the rail industry, and a larger study that evaluates several components of a FMS that was implemented by the Australian Civil Aviation Safety Authority (CASA) for the general aviation sector in 2000.

Rail rates and system costs are important to the profitability of Western Canadian agriculture. This importance is due to the high cost of transporting grain to export position combined with rails cost advantage in relation to other modes of bulk transportation. World grain markets are competitive and any increase in freight rate caused by inefficiency or market power can not be passed on consumers. <p>This thesis introduces and discusses a way to create competition in the rail industry through vertical separation of rolling stock and track. The discussion is motivated by a transactions cost framework, whereby key features of a vertically integrated railway such as we have in Canada are contrasted with those of a vertically separated railway, as is the case today in Sweden. The two systems share common characteristics, but the way system participants interact are ultimately very different. <p>Canadas vertically integrated railway system creates strong incentives for infrastructure investment along with maintenance and congestion management, but a vertically integrated system discourages new competition in the industry. Conversely, the vertically separated Swedish system creates strong incentives for inter-rail competition and improvements in customer service. Canadas rail system is now less subsidized than ever, while the Swedish system still requires significant public outlay, and will need continued government support. <p>Due to its cost structure, the choice of regulation in the rail sector continues to be a trade-off between railway cost recovery and fair rates for shippers. As applied to Canada, the example of Sweden illustrates that a limited access regime in rail can operationally function and reduce market power concerns. An access regime can achieve this reduction by supporting contestable pricing that will limit the ability of railways to price discriminate.

Rail rates and system costs are important to the profitability of Western Canadian agriculture. This importance is due to the high cost of transporting grain to export position combined with rails cost advantage in relation to other modes of bulk transportation. World grain markets are competitive and any increase in freight rate caused by inefficiency or market power can not be passed on consumers. <p>This thesis introduces and discusses a way to create competition in the rail industry through vertical separation of rolling stock and track. The discussion is motivated by a transactions cost framework, whereby key features of a vertically integrated railway such as we have in Canada are contrasted with those of a vertically separated railway, as is the case today in Sweden. The two systems share common characteristics, but the way system participants interact are ultimately very different. <p>Canadas vertically integrated railway system creates strong incentives for infrastructure investment along with maintenance and congestion management, but a vertically integrated system discourages new competition in the industry. Conversely, the vertically separated Swedish system creates strong incentives for inter-rail competition and improvements in customer service. Canadas rail system is now less subsidized than ever, while the Swedish system still requires significant public outlay, and will need continued government support. <p>Due to its cost structure, the choice of regulation in the rail sector continues to be a trade-off between railway cost recovery and fair rates for shippers. As applied to Canada, the example of Sweden illustrates that a limited access regime in rail can operationally function and reduce market power concerns. An access regime can achieve this reduction by supporting contestable pricing that will limit the ability of railways to price discriminate.

Three improved operational amplifiers with low voltage and rail-to-rail constant are proposed. Two of the amplifiers are modified from the amplifier with a level shifting circuit. One improved amplifier has fewer devices, higher speed, and reduced area and the other improved amplifier is added an additional adjustable gain. The third amplifier is a floating voltage controlled voltage source (FVCVS) amplifier, which has reduced area and improved frequency response. The first two level shifting operational amplifiers are designed in a 0.5£gm UMC CMOS process. They use about half number of devices. The supply voltage is 1.3V, and the current consumes just only 22.6¢H of the original circuits. The unity gain frequency increases 56.8%. The slew rate, CMRR and PSRR are higher. The 2nd amplifier still has a rail-to-rail constant gm; however, the gm can be adjusted. The third amplifier uses the 0.35£gm UMC CMOS process with 1.2V operating voltage. The gain-bandwidth product is 53.8¢H larger than the original circuits. No frequency compensation is used and the devices are fewer. The results are obtained in HSPICE simulation.

A rail-to-rail op-amp with high stability over temperature variation at 1-V supply voltage is presented in this thesis. It incorporates a modified CM adapter and a modified bandgap reference. First, the modified CM adapter utilizes a level-shifting technique to shift the input common mode voltage of 0-1 V to the level below 0.1 V. By introducing this circuit as the front-end block of the proposed op-amp, the PMOS differential input stage can be operated appropriately with the rail-to-rail input common mode range. Second, the modified bandgap reference that combines two voltages with opposite temperature coefficients generates a temperature-insensitive bias current to the input stage. Besides, by the technique of cascading a diode with an additional BJT, the junction area of the original diodes can be reduced and in the actual application, fewer parallel-connected BJTs are needed. The two circuits are applied to the proposed op-amp operated at 1-V supply voltage in TSMC 1P4M 0.35£gm CMOS technology. At 25¢J, the dc gain is 78.9 dB and unity-gain bandwidth is 3.73 MHz. The phase margin is 42.9¢X. For the temperature from 0¢J to 75¢J, the frequency response is temperature-insensitive and the dc gain variation is 2dB. The layout view of the proposed op-amp is also presented and the area is 0.2 mm2.