10,890 research outputs found
Assessment of practicality of remote sensing techniques for a study of the effects of strip mining in Alabama
Because of the volume of coal produced by strip mining, the proximity of mining operations, and the diversity of mining methods (e.g. contour stripping, area stripping, multiple seam stripping, and augering, as well as underground mining), the Warrior Coal Basin seemed best suited for initial studies on the physical impact of strip mining in Alabama. Two test sites, (Cordova and Searles) representative of the various strip mining techniques and environmental problems, were chosen for intensive studies of the correlation between remote sensing and ground truth data. Efforts were eventually concentrated in the Searles Area, since it is more accessible and offers a better opportunity for study of erosional and depositional processes than the Cordova Area
Controlling the accuracy of the density matrix renormalization group method: The Dynamical Block State Selection approach
We have applied the momentum space version of the Density Matrix
Renormalization Group method (-DMRG) in quantum chemistry in order to study
the accuracy of the algorithm in the new context. We have shown numerically
that it is possible to determine the desired accuracy of the method in advance
of the calculations by dynamically controlling the truncation error and the
number of block states using a novel protocol which we dubbed Dynamical Block
State Selection (DBSS). The relationship between the real error and truncation
error has been studied as a function of the number of orbitals and the fraction
of filled orbitals. We have calculated the ground state of the molecules
CH, HO, and F as well as the first excited state of CH. Our
largest calculations were carried out with 57 orbitals, the largest number of
block states was 1500--2000, and the largest dimensions of the Hilbert space of
the superblock configuration was 800.000--1.200.000.Comment: 12 page
Multi-objective improvement of software using co-evolution and smart seeding
Optimising non-functional properties of software is an important part of the implementation process. One such property is execution time, and compilers target a reduction in execution time using a variety of optimisation techniques. Compiler optimisation is not always able to produce semantically equivalent alternatives that improve execution times, even if such alternatives are known to exist. Often, this is due to the local nature of such optimisations. In this paper we present a novel framework for optimising existing software using a hybrid of evolutionary optimisation techniques. Given as input the implementation of a program or function, we use Genetic Programming to evolve a new semantically equivalent version, optimised to reduce execution time subject to a given probability distribution of inputs. We employ a co-evolved population of test cases to encourage the preservation of the program’s semantics, and exploit the original program through seeding of the population in order to focus the search. We carry out experiments to identify the important factors in maximising efficiency gains. Although in this work we have optimised execution time, other non-functional criteria could be optimised in a similar manner
Observations of the 8 December 1987 occultation of AG+40 deg 0783 by 324 Bamberga
The occultation of AG+40 deg 0783 by 324 Bamberga on 8 December 1987 was observed at 13 sites in the United States, Japan, and China. At four sites the event was observed photoelectrically; the other observations were visual. A least-squares fit of a circular limb profile to the data gives a diameter of 227.6 + or - 1.9 km. However, this solution is inconsistent with a negative visual observation near the northern edge of the ground track. The inconsistency cannot be removed by assuming an elliptical profile. The data suggest that Bamberga, despite its low-amplitude lightcurve, may depart significantly from a spherical or ellipsoidal shape. The asteroid also appears to be at least 10 percent smaller than indicated by infrared radiometry
Eulerian simulation of the fluid dynamics of helicopter brownout
A computational model is presented that can be used to simulate the development of the dust cloud
that can be entrained into the air when a helicopter is operated close to the ground in desert or dusty
conditions. The physics of this problem, and the associated pathological condition known as ‘brownout’
where the pilot loses situational awareness as a result of his vision being occluded by dust suspended in the
flow around the helicopter, is acknowledged to be very complex. The approach advocated here involves
an approximation to the full dynamics of the coupled particulate-air system. Away from the ground, the
model assumes that the suspended particles remain in near equilibrium under the action of aerodynamic
forces. Close to the ground, this model is replaced by an algebraic sublayer model for the saltation and
entrainment process. The origin of the model in the statistical mechanics of a distribution of particles
governed by aerodynamic forces allows the validity of the method to be evaluated in context by comparing
the physical properties of the suspended particulates to the local properties of the flow field surrounding
the helicopter. The model applies in the Eulerian frame of reference of most conventional Computational
Fluid Dynamics codes and has been coupled with Brown’s Vorticity Transport Model. Verification of the
predictions of the coupled model against experimental data for particulate entrainment and transport in
the flow around a model rotor are encouraging. An application of the coupled model to analyzing the
differences in the geometry and extent of the dust clouds that are produced by single main rotor and
tandem-rotor configurations as they decelerate to land has shown that the location of the ground vortex
and the size of any regions of recirculatory flow, should they exist, play a primary role in governing the
extent of the dust cloud that is created by the helicopter
Individual Rights, Economic Transactions, and Recognition: A Legal Approach to Social Economics
Modernity brought the idea of individual property rights as a com- plex phenomenon. However, economics adopted a simplistic view of property as a fundamental institution, understating the complex interaction of different rights and obligations that frame the legal environment of economic processes with an insufficiently elaborated tool. Here, a more elaborate view of legal elements will be propose
Delineation of individual human chromosomes in metaphase and interphase cells by in situ suppression hybridization using recombinant DNA libraries
A method of in situ hybridization for visualizing individual human chromosomes from pter to qter, both in metaphase spreads and interphase nuclei, is reported. DNA inserts from a single chromosomal library are labeled with biotin and partially preannealed with a titrated amount of total human genomic DNA prior to hybridization with cellular or chromosomal preparations. The cross-hybridization of repetitive sequences to nontargeted chromosomes can be markedly suppressed under appropriate preannealing conditions. The remaining single-stranded DNA is hybridized to specimens of interest and detected with fluorescent or enzymelabeled avidin conjugates following post-hybridization washes. DNA inserts from recombinant libraries for chromosomes 1, 4, 7, 8, 13, 14, 18, 20, 21, 22, and X were assessed for their ability to decorate specifically their cognate chromosome; most libraries proved to be highly specific. Quantitative densitometric analyses indicated that the ratio of specific to nonspecific hybridization signal under optimal preannealing conditions was at least 8:1. Interphase nuclei showed a cohesive territorial organization of chromosomal domains, and laserscanning confocal fluorescence microscopy was used to aid the 3-D visualization of these domains. This method should be useful for both karyotypic studies and for the analysis of chromosome topography in interphase cells
Early stage morphology of quench condensed Ag, Pb and Pb/Ag hybrid films
Scanning Tunneling Microscopy (STM) has been used to study the morphology of
Ag, Pb and Pb/Ag bilayer films fabricated by quench condensation of the
elements onto cold (T=77K), inert and atomically flat Highly Oriented Pyrolytic
Graphite (HOPG) substrates. All films are thinner than 10 nm and show a
granular structure that is consistent with earlier studies of QC films. The
average lateral diameter, , of the Ag grains, however, depends on
whether the Ag is deposited directly on HOPG ( = 13 nm) or on a Pb
film consisting of a single layer of Pb grains ( = 26.8 nm). In
addition, the critical thickness for electrical conduction () of Pb/Ag
films on inert glass substrates is substantially larger than for pure Ag films.
These results are evidence that the structure of the underlying substrate
exerts an influence on the size of the grains in QC films. We propose a
qualitative explanation for this previously unencountered phenomenon.Comment: 11 pages, 3 figures and one tabl
Regularity of higher codimension area minimizing integral currents
This lecture notes are an expanded version of the course given at the
ERC-School on Geometric Measure Theory and Real Analysis, held in Pisa,
September 30th - October 30th 2013. The lectures aim to explain the main steps
of a new proof of the partial regularity of area minimizing integer rectifiable
currents in higher codimension, due originally to F. Almgren, which is
contained in a series of papers in collaboration with C. De Lellis (University
of Zurich).Comment: This text will appear in "Geometric Measure Theory and Real
Analysis", pp. 131--192, Proceedings of the ERC school in Pisa (2013), L.
Ambrosio Ed., Edizioni SNS (CRM Series
Systematic Cu-63 NQR studies of the stripe phase in La(1.6-x)Nd(0.4)Sr(x)CuO(4) for 0.07 <= x <= 0.25
We demonstrate that the integrated intensity of Cu-63 nuclear quadrupole
resonance (NQR) in La(1.6-x)Nd(0.4)Sr(x)CuO(4) decreases dramatically below the
charge-stripe ordering temperature T(charge). Comparison with neutron and X-ray
scattering indicates that the wipeout fraction F(T) (i.e. the missing fraction
of the integrated intensity of the NQR signal) represents the charge-stripe
order parameter. The systematic study reveals bulk charge-stripe order
throughout the superconducting region 0.07 <= x <= 0.25. As a function of the
reduced temperature t = T/T(charge), the temperature dependence of F(t) is
sharpest for the hole concentration x=1/8, indicating that x=1/8 is the optimum
concentration for stripe formation.Comment: 10 pages of text and captions, 11 figures in postscript. Final
version, with new data in Fig.
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