26,814 research outputs found
High-efficiency cell concepts on low-cost silicon sheets
The limitations on sheet growth material in terms of the defect structure and minority carrier lifetime are discussed. The effect of various defects on performance are estimated. Given these limitations designs for a sheet growth cell that will make the best of the material characteristics are proposed. Achievement of optimum synergy between base material quality and device processing variables is proposed. A strong coupling exists between material quality and the variables during crystal growth, and device processing variables. Two objectives are outlined: (1) optimization of the coupling for maximum performance at minimal cost; and (2) decoupling of materials from processing by improvement in base material quality to make it less sensitive to processing variables
An Age-Period-Cohort Database of Inter-Regional Migration in Australia and Britain, 1976-96
Report prepared as part of a collaborative project on "Migration Trends in Australia and Britain: Levels and Trends in an Age-Period-Cohort Framework" funded by the Economic and Social Research Council and the Australian Research Council.
This paper describes the way in which parallel databases of inter-regional migration flows for Australia and Britain, classified by five year ages and birth cohorts for four five year periods between 1976 and 1996. The data processing involves estimation of migration data for comparable spatial units, the reduction of the number of those units to a reduced set for ease of analysis, the extraction of migration data from official data files supplied by the Australian Bureau of Statistics and the Office for National Statistics, and the filling of gaps in these files through iterative proportional fitting for some of the British data. The final stage in preparation of the migration databases was to estimate the numbers of transitions (Australia) or movements (Britain) for age-period-cohort spaces. In principle, this last estimation involves a fairly simple interpolation or aggregation of age-time classified migration data, but in practice a great deal of detailed attention is required. A final section specifies the populations at risk to be used for each age-period-cohort observation plan to compute migration intensities
Abundance and Partitioning of OH in a High-pressure Magmatic System: Megacrysts from the Monastery Kimberlite, South Africa
Concentrations of OH, and major and trace elements were determined in a suite of mantle-derived megacrysts that represent the crystallization products of a kimberlite-like magma at ~5 GPa and ~1400ā1100Ā°C. OH concentrations, determined by single-crystal Fourier transform infrared spectroscopy, display the following ranges (ppmw H2O): olivine 54ā262, orthopyroxene 215ā263, garnet 15ā74, clinopyroxene 195ā620, and zircon 28ā34. High OH concentrations in olivine imply mantle conditions of origin, with limited H loss during ascent. OH is consistently correlated with megacryst composition, exhibiting trends with Mg-number that are similar to those of other minor and trace elements and indicating a record of high-pressure magmatic evolution. H substitution is not coupled to minor elements in olivine, but may be in ortho- and clinopyroxene. The OHāMg-number trends of garnet and clinopyroxene show inflections related to co-precipitation of ilmenite, suggesting minor element (Ti) influence on OH partitioning. During differentiation, relative OH enrichment in clinopyroxene and olivine is consistent with proportional dependence on water activity, whereas that in garnet suggests a higher power-law dependence and/or influence of temperature. Inter-mineral distribution coefficients for OH between cpx, opx, olivine and zircon are thus constant, whereas partitioning between these minerals and garnet shows a factor 4ā10 variation, correlated regularly with composition (and temperature). Calculation of solidāmelt partition coefficients for H at 5 GPa over a range of magmatic evolution from 1380 to 1250Ā°C yields: ol 0Ā·0053ā0Ā·0046, opx 0Ā·0093ā0Ā·0059, cpx 0Ā·016ā0Ā·013, gt 0Ā·0014ā0Ā·0003, bulk (garnet lherzoliteāmelt) 0Ā·0063ā0Ā·0051. These are consistent with experimental studies and similar to values inferred from mid-ocean ridge basalt geochemistry, confirming the moderate incompatibility of H in mantle melting
Harmonising Databases for the Cross National Study of Internal Migration: Lessons from Australia and Britain
This project involves the development of a Web interface to origin-destination statistics from the 1991 Census (in a form that will be compatible with planned 2001 outputs). It provides the user with a set of screen-based tools for setting the parameters governing each data extraction (data set, areas, variables) in the form of a query. Traffic light icons are used to signal what the user has set so far and what remains to be done. There are options to extract different types of flow data and to generate output in different formats. The system can now be used to access the interaction flow data contained in the 1991 Special Migration Statistics Sets 1 and 2 and Special Workplace Statistics Set C. WICID has been demonstrated at the Origin-Destination Statistics Roadshows organised by GRO Scotland and held during May/June 2000 and the Census Offices have expressed interest in using the software in the Census Access Project
Bell's Jump Process in Discrete Time
The jump process introduced by J. S. Bell in 1986, for defining a quantum
field theory without observers, presupposes that space is discrete whereas time
is continuous. In this letter, our interest is to find an analogous process in
discrete time. We argue that a genuine analog does not exist, but provide
examples of processes in discrete time that could be used as a replacement.Comment: 7 pages LaTeX, no figure
Two-Stage LASSO ADMM Signal Detection Algorithm For Large Scale MIMO
This paper explores the benefit of using some of the machine learning
techniques and Big data optimization tools in approximating maximum likelihood
(ML) detection of Large Scale MIMO systems. First, large scale MIMO detection
problem is formulated as a LASSO (Least Absolute Shrinkage and Selection
Operator) optimization problem. Then, Alternating Direction Method of
Multipliers (ADMM) is considered in solving this problem. The choice of ADMM is
motivated by its ability of solving convex optimization problems by breaking
them into smaller sub-problems, each of which are then easier to handle.
Further improvement is obtained using two stages of LASSO with interference
cancellation from the first stage. The proposed algorithm is investigated at
various modulation techniques with different number of antennas. It is also
compared with widely used algorithms in this field. Simulation results
demonstrate the efficacy of the proposed algorithm for both uncoded and coded
cases.Comment: 5 pages, 4 figure
Objective Classification of Galaxy Spectra using the Information Bottleneck Method
A new method for classification of galaxy spectra is presented, based on a
recently introduced information theoretical principle, the `Information
Bottleneck'. For any desired number of classes, galaxies are classified such
that the information content about the spectra is maximally preserved. The
result is classes of galaxies with similar spectra, where the similarity is
determined via a measure of information. We apply our method to approximately
6000 galaxy spectra from the ongoing 2dF redshift survey, and a mock-2dF
catalogue produced by a Cold Dark Matter-based semi-analytic model of galaxy
formation. We find a good match between the mean spectra of the classes found
in the data and in the models. For the mock catalogue, we find that the classes
produced by our algorithm form an intuitively sensible sequence in terms of
physical properties such as colour, star formation activity, morphology, and
internal velocity dispersion. We also show the correlation of the classes with
the projections resulting from a Principal Component Analysis.Comment: submitted to MNRAS, 17 pages, Latex, with 14 figures embedde
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