Coal pressurization and feeding: Use of a lock hopper system

Operation of a synthane gasifier pilot plant is discussed. The specific problems experienced with the operation of the Petrocarb system at the pilot plant are described along with modifications made to improve its performance

Wheel/Rail Contact Isolation Due to Track Contamination

An experimental study has been carried out to investigate the effect of sanding on the electrical isolation of a wheel/rail contact. Sand is applied to the wheel/rail interface to increase adhesion in both braking and traction. Train detection, for signalling purposes, can be by means of track circuits. Signalling block occupancy is triggered by the wheelset of the train ‘shorting out’ the track circuit. Sand in the wheel/rail interface means that contact between the wheelsets and the track may be compromised, inhibiting train identification. Static tests were performed using sections cut from wheels and rail and dynamic tests on a twin disc machine where rail and wheel steel discs are loaded together and driven under controlled conditions of rolling and slip. The electrical circuit used was a simplified simulation of the TI21 track circuit. The application of sand was carried out under a range of mild and severe test conditions. The results indicated that a transition exists in the amount of sand applied, below which there is a measurable, but not severe, change in voltage, but above which the contact conductance decreases by an order of magnitude. A model of electrical isolation has been developed assuming either full disc separation by a sand layer or partial disc contact with some sand present. Idealisations inherent in both test methods mean that they represent a severe case. Given these limitations, it is likely that the test methods, at their present stage of development, should be used as a means to qualitatively assess the relative effects on electrical isolation of different contaminants

Selecting communication media for distributed communities

Within the 'Virtual Mobility and Distributed Laboratories' project three naturalistic case studies of distributed research communities were conducted with a focus on the communication media used. The findings provide insight into relationships between the different media that the communities selected, and the different activities to which these media contributed. It is suggested that these findings are also relevant for distributed groups in which collaborative learning is the primary aim. A framework is presented for understanding and recommending selections of media for particular kinds of tasks, which is derived by integrating Media‐richness Theory and Activity Theory. This framework indicates how task/media fit may be achieved while taking into account the evolving character of activities in a distributed community. Some implications of the framework for collaborative distance learning are highlighted.\ud \u

Strange-quark Current in the Nucleon from Lattice QCD

The contribution of the strange-quark current to the electromagnetic form factors of the nucleon is studied using lattice QCD. The strange current matrix elements from our lattice calculation are analyzed in two different ways, the differential method used in an earlier work by Wilcox and a cumulative method which sums over all current insertion times. The preliminary results of our simulation indicate the importance of high statistics, and that consistent results between the varying analysis methods can be achieved. Although this simulation does not yet yield a number that can be compared to experiment, several criteria useful in assessing the robustness of a signal extracted from a noisy background are presented.Comment: 12 pages, 9 figures, Presented at EMI 200

Viking and STP P78-2 electrostatic charging designs and testing

The design provisions of the Viking and the P78-2 (SCATHA) vehicles and a mathematical analysis of the effect of arcing on typical interface circuits are given. Results of verification testing of the analysis are presented as well as vehicle testing for tolerance to arcing

Design overview of fiber-reinforced superalloy composites for the Space Shuttle main engine

This preliminary design study evaluated the potential of fiber-reinforced superalloys (FRS) for hot-section components of Space Shuttle Main Engine turbopumps. Emphasis was placed on uncooled turbine blades, with a more limited evaluation of FRS turbine stator vanes. The study included FRS properties evaluation, current structural design capability, and preliminary design and structural analysis. In addition, key technology needs were identified, and a plan was generated to develop operational hardware for advanced versions of the SSME. Based on projections of design properties for FRS composites comprising 50 volume percent of W-4Re-0.38Hf-0.02C wire filaments in a ductile superalloy matrix, it was concluded that FRS turbine blades offer the potential of significant improved operating life and higher temperature capability over the MAR-M-246(Hf) (DS) blades currently used in the SSME

Isospin violation in the vector form factors of the nucleon

A quantitative understanding of isospin violation is an increasingly important ingredient for the extraction of the nucleon's strange vector form factors from experimental data. We calculate the isospin violating electric and magnetic form factors in chiral perturbation theory to leading and next-to-leading order respectively, and we extract the low-energy constants from resonance saturation. Uncertainties are dominated largely by limitations in the current knowledge of some vector meson couplings. The resulting bounds on isospin violation are sufficiently precise to be of value to on-going experimental studies of the strange form factors.Comment: 13 pages, 8 figures, uses RevTe