114,048 research outputs found
Development of a Straw Tube Chamber with Pickup-Pad Readout
We have developed a straw tube chamber with pickup-pad readout. The mechanism
for signal pickup, the size of the pickup signal, and the distribution of
signals among neighboring pads are discussed. We have tested a prototype
chamber in a beamtest at Brookhaven National laboratory and have measured
chamber efficiencies in excess of 99%.Comment: 7 pages, 8 figures, 2 tables. Talk presented at DPF '99 Meeting, UCL
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Coupled thermo-mechanical damage modelling for structural steel in fire conditions
This paper aims at developing a coupled thermo-mechanical damage model for structural 6 steel at elevated temperatures. The need for adequate modelling of steel deterioration behaviour 7 remains a challenging task in structural fire engineering because of the complexity inherent in 8 the damage states of steel under combined actions of mechanical and fire loading. A fully three9 dimensional damage-coupled constitutive model is developed in this work based on the hypothesis 10 of effective stress space and isotropic damage theory. The new coupling model, adapted from 11 an enhanced Lemaitre’s ductile damage equation and taking into account temperature-dependent 12 thermal degradation, is a phenomenological approach where the underlying mechanisms that govern 13 the damage processes have been retained. The proposed damage model comprises a limited number 14 of parameters that could be identified using unloading slopes of stress-strain relationships through 15 tensile coupon tests. The proposed damage model is successfully implemented in the finite element 16 software ABAQUS and validated against a comprehensive range of experimental results. The 17 damage-affected structural response is accurately reproduced under various loading conditions and 18 a wide temperature range, demonstrating that the proposed damage model is a useful tool in giving a 19 realistic representation of steel deterioration behaviour for structural fire engineering applications
Manual of phosphoric acid fuel cell power plant optimization model and computer program
An optimized cost and performance model for a phosphoric acid fuel cell power plant system was derived and developed into a modular FORTRAN computer code. Cost, energy, mass, and electrochemical analyses were combined to develop a mathematical model for optimizing the steam to methane ratio in the reformer, hydrogen utilization in the PAFC plates per stack. The nonlinear programming code, COMPUTE, was used to solve this model, in which the method of mixed penalty function combined with Hooke and Jeeves pattern search was chosen to evaluate this specific optimization problem
Phosphoric acid fuel cell power plant system performance model and computer program
A FORTRAN computer program was developed for analyzing the performance of phosphoric acid fuel cell power plant systems. Energy mass and electrochemical analysis in the reformer, the shaft converters, the heat exchangers, and the fuel cell stack were combined to develop a mathematical model for the power plant for both atmospheric and pressurized conditions, and for several commercial fuels
Manual of phosphoric acid fuel cell power plant cost model and computer program
Cost analysis of phosphoric acid fuel cell power plant includes two parts: a method for estimation of system capital costs, and an economic analysis which determines the levelized annual cost of operating the system used in the capital cost estimation. A FORTRAN computer has been developed for this cost analysis
Manual of phosphoric acid fuel cell stack three-dimensional model and computer program
A detailed distributed mathematical model of phosphoric acid fuel cell stack have been developed, with the FORTRAN computer program, for analyzing the temperature distribution in the stack and the associated current density distribution on the cell plates. Energy, mass, and electrochemical analyses in the stack were combined to develop the model. Several reasonable assumptions were made to solve this mathematical model by means of the finite differences numerical method
The relativistic Iron K-alpha line from an accretion disc onto a static non-baryonic compact object
This paper continues the study of the properties of an accretion disc
rotating around a non-baryonic (assumed super-massive) compact object. This
kind of objects, generically known as boson stars, were earlier proposed as a
possible alternative scenario to the existence of super-masive black holes in
the center of every galaxy. A dilute boson star has also been proposed as a
large part of the non-baryonic dark matter, flattening galactic rotational
velocities curves. In this contribution, we compute the profile of the emission
lines of Iron; its shape has been for long known as a useful diagnosis of the
space-time geometry. We compare with the case of a Schwarzschild black hole,
concluding that the differences are observationally distinguishable.Comment: 14 pages, 7 figure
Direct Measurement of Quantum Dot Spin Dynamics using Time-Resolved Resonance Fluorescence
We temporally resolve the resonance fluorescence from an electron spin
confined to a single self-assembled quantum dot to measure directly the spin's
optical initialization and natural relaxation timescales. Our measurements
demonstrate that spin initialization occurs on the order of microseconds in the
Faraday configuration when a laser resonantly drives the quantum dot
transition. We show that the mechanism mediating the optically induced
spin-flip changes from electron-nuclei interaction to hole-mixing interaction
at 0.6 Tesla external magnetic field. Spin relaxation measurements result in
times on the order of milliseconds and suggest that a magnetic field
dependence, due to spin-orbit coupling, is sustained all the way down to 2.2
Tesla.Comment: An additional EPAPS file in PDF format is available for download at
the publications section of our website
http://www.amop.phy.cam.ac.uk/amop-ma
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