32,652 research outputs found
A model-based constraint on CO<sub>2</sub> fertilisation
We derive a constraint on the strength of CO2 fertilisation of the terrestrial biosphere through a âtop-downâ approach, calibrating Earth system model parameters constrained by the post-industrial increase of atmospheric CO2 concentration. We derive a probabilistic prediction for the globally averaged strength of CO2 fertilisation in nature, for the period 1850 to 2000 AD, implicitly net of other limiting factors such as nutrient availability. The approach yields an estimate that is independent of CO2 enrichment experiments. To achieve this, an essential requirement was the incorpo- ration of a land use change (LUC) scheme into the GENIE Earth system model. Using output from a 671-member ensemble of transient GENIE simulations, we build an emulator of the change in atmospheric CO2 concentration change since the preindustrial period. We use this emulator to sample the 28-dimensional input parameter space. A Bayesian calibration of the emulator output suggests that the increase in gross primary productivity (GPP) in response to a doubling of CO2 from preindustrial values is very likely (90 % confidence) to exceed 20 %, with a most likely value of 40â60 %. It is important to note that we do not represent all of the possible contributing mechanisms to the terrestrial sink. The missing processes are subsumed into our calibration of CO2 fertilisation, which therefore represents the combined effect of CO2 fertilisation and additional missing processes. If the missing processes are a net sink then our estimate represents an upper bound. We derive calibrated estimates of carbon fluxes that are consistent with existing estimates. The present-day landâatmosphere flux (1990â2000) is estimated at â0.7 GTC yrâ1 (likely, 66 % confidence, in the range 0.4 to â1.7 GTC yrâ1). The present-day oceanâatmosphere flux (1990â2000) is estimated to be â2.3 GTC yrâ1 (likely in the range â1.8 to â2.7 GTC yrâ1). We estimate cumulative net land emissions over the post-industrial period (land use change emissions net of the CO2 fertilisation and climate sinks) to be 66 GTC, likely to lie in the range 0 to 128 GTC
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Adapting user interfaces for visually disabled users
Recent developments in the design of human-machine interfaces have resulted in interfaces which make access to computer-based equipment more difficult for visually disabled people. The aim of this project was to explore whether it is possible to adapt such interfaces so as to make them usable by people who cannot see a screen.
The approach adopted was based upon two principles: the replacement of visual interlace entities by auditory analogues and appropriately constraining the resultant interlace. Two forms of sound were used to embody the auditory interface: musical tones and synthetic speech. The 'auditory screen' so produced consists of a grid of 'auditory objects', each of which is associated with a spatial location, a tone, a name and an action. In order to test the principles a word processing program was designed and implemented to demonstrate how a visual program might be adapted to be accessed through such an interface.
This program was evaluated with the assistance of a number of visually disabled testers. They were trained to use the word processor through completing a graded set of exercises. Data were obtained in a number of ways during and after the completion of the exercises. Since the auditory interface had some novel components, special evaluation methods were applied. The nature of the interaction was analyzed, using an approach based on work on keystroke models of visual interfaces. This yielded a simple model of the 'hand-ear' coordination employed, which forms a basis for prediction of user behaviour. It was also necessary to evaluate aspects of the program, such as ease-of-learning and these were investigated by interviewing the subjects. The results demonstrate that the approach is viable. The thesis also discusses a number of problems in using such an interface, most of which are related to the memory load on the user
A Green's function decoupling scheme for the Edwards fermion-boson model
Holes in a Mott insulator are represented by spinless fermions in the
fermion-boson model introduced by Edwards. Although the physically interesting
regime is for low to moderate fermion density the model has interesting
properties over the whole density range. It has previously been studied at
half-filling in the one-dimensional (1D) case by numerical methods, in
particular exact diagonalization and density matrix renormalization group
(DMRG). In the present study the one-particle Green's function is calculated
analytically by means of a decoupling scheme for the equations of motion, valid
for arbitrary density in 1D, 2D and 3D with fairly large boson energy and zero
boson relaxation parameter. The Green's function is used to compute some ground
state properties, and the one-fermion spectral function, for fermion densities
n=0.1, 0.5 and 0.9 in the 1D case. The results are generally in good agreement
with numerical results obtained by DMRG and dynamical DMRG and new light is
shed on the nature of the ground state at different fillings. The Green's
function approximation is sufficiently successful in 1D to justify future
application to the 2D and 3D cases.Comment: 19 pages, 7 figures, final version with updated reference
Predicting Natural Frequencies Of A Hydrodynamically Lubricated Journal Bearing With Constant Oil Supply Pressure
The analytical and experimental investigations reported here deal with the natural frequencies and system behavior of a full journal bearing subjected to a small sinusoidal load superimposed on a large unidirectional static load. The analysis, verified by experimentation, shows that the bearing can be regarded as two independent second-order systems acting perpendicular to each other. The variable coefficients of the equations of motion cause the bearing to behave as an underdamped system for low values of static eccentricity ratio to, and as an overdamped system for intermediate values of to. The bearing tends to be unstable above a particular to. Further analysis is needed to determine the effects resulting from changing the oil inlet pressure. © 1976 by ASME
Analysis of United Kingdom Off-Highway Construction Machinery Market and Its Consumers Using New-Sales Data
The off-highway construction machinery market and its consumers have attracted minimal previous research. This study addresses that void by analyzing annual United Kingdom (UK) (volume/portfolio) new-sales data for the 10 most popular products within that market, 1990â2010 inclusive. Graphical, descriptive statistical, Pearson-correlational, autocorrelational, and elementary modeling are employed to identify contrasts in sales regarding (1) high- and low-volume items; (2) growth trends and significant recessionary effects on volumes; (3) a demand change point circa 1997, since when annual product portfolio has changed little; and (4) product associations in consumer demand. Significant association is demonstrated between demand and construction output, especially with the value of new housing. Subsequently, consumption of wheeled loaders is modeled using construction volume, and demand for mini and crawler excavators is modeled using new-housing data. Time series trends for these machinery types are presented and forecast through 2015. The primary contribution of this study is a deeper understanding of the UK new-machinery market and the predilections of its consumers over the last two decades (to present)
First Calculation of Hyperon Axial Couplings from Lattice QCD
In this work, we report the first lattice calculation of hyperon axial
couplings, using the 2+1-flavor MILC configurations and domain-wall fermion
valence quarks. Both the and axial couplings are computed for
the first time in lattice QCD. In particular we find that and .Comment: 5 pages, 2 figure
Magnetic properties of strongly disordered electronic systems
We present a unified, global perspective on the magnetic properties of
strongly disordered electronic systems, with special emphasis on the case where
the ground state is metallic. We review the arguments for the instability of
the disordered Fermi liquid state towards the formation of local magnetic
moments, and argue that their singular low temperature thermodynamics are the
``quantum Griffiths'' precursors of the quantum phase transition to a metallic
spin glass; the local moment formation is therefore not directly related to the
metal-insulator transition. We also review the the mean-field theory of the
disordered Fermi liquid to metallic spin glass transition and describe the
separate regime of ``non-Fermi liquid'' behavior at higher temperatures near
the quantum critical point. The relationship to experimental results on doped
semiconductors and heavy-fermion compounds is noted.Comment: 25 pages; Contribution to the Royal Society Discussion Meeting on
"The Metal-Non Metal Transition in Macroscopic and Microscopic Systems",
March 5-6, 199
Ethical and compliance-competence evaluation: a key element of sound corporate governance
Motivated by the ongoing post-Enron refocusing on corporate governance and the shift by the Financial Services Authority (FSA) in the UK to promoting compliance- competence within the financial services sector, this paper demonstrates how template analysis can be used as a tool for evaluating compliance-competence. Focusing on the ethical dimension of compliance-competence, we illustrate how this can be subjectively appraised. We propose that this evaluation technique could be utilised as a starting point in informing senior management of corporate governance issues and be used to monitor and demonstrate key compliance and ethical aspects of an institution to external stakeholders and regulators
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