575 research outputs found
Characterization of high-fracture toughness K-fluorrichterite-fluorapatite glass ceramics
Stoichiometric K-fluorrichterite (Glass A) and the same composition with 2 mol% P2O5 added (Glass B) were prepared and then heat-treated isothermally from 550°1000°C with 50°C intervals. Samples were characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The biaxial flexural strength and indentation fracture toughness of heat-treated glass specimens were also determined for both materials. XRD traces and TEM images showed similar phase evolution and fine microstructures for both systems at ≤950°C, with mica and diopside reacting with residual glass to form K-fluorrichterite as the temperature was increased from 650°C. However, in Glass B, fluorapatite was also present at >800°C. In contrast, coarser microstructures were observed at 1000°C, with larger K-fluorrichterite (20 μm) and enstatite (10 μm) crystals in Glasses A and B, respectively. The highest fracture toughness (2.69 ± 0.01 MPa·m(1/2)) and biaxial strength (242.6 ± 3.6 MPa) were recorded for Glass B heat-treated at 1000°C. This was attributed to the presence of enstatite coupled with an interlocked lath-like crystalline microstructure
Giving credit to the microlenders. Formal microlending, credit constraints and adverse selection: a case study of shrimp farmers in Bangladesh
Smallholder farmers have long been denied access to formal credit, largely because of the high administrative fees associated with loans. A possible solution to this problem, which has become increasingly popular, is the use of microcredit financing, where innovative means of securing the loans, such as peer monitoring, are used. This paper examines the effectiveness of formal microcredit schemes as compared to the traditional informal credit sources in a rural shrimp farming district of Bangladesh. We compare the two types of credit by studying the technical and allocative efficiencies of the two groups of borrowers. The findings suggest that farmers using both types of microcredit have difficulty accessing credit, often over-utilising labour in order to reduce the need for inputs that require cash at the beginning of the season, creating inefficiencies in production. However, the informal lenders, with their closer ties to individual farmers, were more successful in identifying those small-holders most likely to make the best use of the borrowed funds. Thus, although formal microcredit schemes do not impose the high administrative fees of traditional formal lending, they do not necessarily solve the problem of how to select successful borrowers.Economics, Bangladesh, Shrimp Farming, Fisheries, Community/Rural/Urban Development, Crop Production/Industries, Environmental Economics and Policy, Financial Economics, Livestock Production/Industries,
Expanding the scope of LCA to include 'societal value': A framework and methodology for assessing positive product impacts
As resources become scarcer, efficiency improvements alone will not bridge the widening gap between supply and demand, resulting in the need for additional non-financial mechanisms to ensure the fairer allocation of resources. This paper asserts that, in the future, companies will need to demonstrate their products' positive contribution to society as well as minimising their negative environmental/soci
al impacts. A review and analysis of existing tools and assessment methodologies identifies current capabilities and highlights the need for 'Societal Value'
assessment that considers both quantitative and qualitative factors .This paper concludes by proposing a systematic
framework for addressing the 'Societal Value' of products as part of an integrate sustainability assessment and allows the evaluation and comparison beyond products' shared functionality
Logarithmic deformations of the rational superpotential/Landau-Ginzburg construction of solutions of the WDVV equations
The superpotential in the Landau-Ginzburg construction of solutions to the Witten-Dijkgraaf-Verlinde-Verlinde (or WDVV) equations is modified to include logarithmic terms. This results in deformations - quadratic in the deformation parameters- of the normal prepotential solutions of the WDVV equations. Such solutions satisfy various pseudo-quasi-homogeneity conditions, on assigning a notional weight to the deformation parameters. These solutions originate in the so-called `water-bag' reductions of the dispersionless KP hierarchy. This construction includes, as a special case, deformations which are polynomial in the flat coordinates, resulting in a new class of polynomial solutions of the WDVV equations
Combinatorial Alexander Duality -- a Short and Elementary Proof
Let X be a simplicial complex with the ground set V. Define its Alexander
dual as a simplicial complex X* = {A \subset V: V \setminus A \notin X}. The
combinatorial Alexander duality states that the i-th reduced homology group of
X is isomorphic to the (|V|-i-3)-th reduced cohomology group of X* (over a
given commutative ring R). We give a self-contained proof.Comment: 7 pages, 2 figure; v3: the sign function was simplifie
Equation of state and initial temperature of quark gluon plasma at RHIC
In gold-gold collisions of the Relativistic Heavy Ion Collider (RHIC) a
perfect fluid of quarks, sometimes called the strongly interacting quark gluon
plasma (sQGP) is created for an extremely short time. The time evolution of
this fluid can be described by hydrodynamical models. After expansion and
cooling, the freeze-out happens and hadrons are created. Their distribution
reveals information about the final state of the fluid. To investigate the time
evolution one needs to analyze penetrating probes, such as direct photon
observables. Transverse momentum distributions of low energy direct photons
were mesured in 2010 by PHENIX, while azimuthal asymmetry in 2011. These
measurements can be compared to hydrodynamics to determine the equation of
state and the initial temperature of sQGP. In this paper we analyze an 1+3
dimensional solution of relativistic hydrodynamics. We calculate momentum
distribution, azimuthal asymmetry and momentum correlations of direct photons.
Based on earlier fits to hadronic spectra, we compare photon calculations to
measurements to determine the equation of state and the initial temperature of
sQGP. We find that the initial temperature in the center of the fireball is
507+-12 MeV, while for the sound speed we get a speed of sound of 0.36+-0.02.
We also estimate a systematic error of these results. We find that the measured
azimuthal asymmetry is also not incompatible with this model, and predict a
photon source that is significantly larger in the out direction than in the
side direction.Comment: 12 pages, 4 figures. This work was supported by the OTKA grant
NK-73143 and NK-101438 and M. Csanad's Bolyai scholarshi
On Eigenvalues of the sum of two random projections
We study the behavior of eigenvalues of matrix P_N + Q_N where P_N and Q_N
are two N -by-N random orthogonal projections. We relate the joint eigenvalue
distribution of this matrix to the Jacobi matrix ensemble and establish the
universal behavior of eigenvalues for large N. The limiting local behavior of
eigenvalues is governed by the sine kernel in the bulk and by either the Bessel
or the Airy kernel at the edge depending on parameters. We also study an
exceptional case when the local behavior of eigenvalues of P_N + Q_N is not
universal in the usual sense.Comment: 14 page
Quantum Tomography under Prior Information
We provide a detailed analysis of the question: how many measurement settings
or outcomes are needed in order to identify a quantum system which is
constrained by prior information? We show that if the prior information
restricts the system to a set of lower dimensionality, then topological
obstructions can increase the required number of outcomes by a factor of two
over the number of real parameters needed to characterize the system.
Conversely, we show that almost every measurement becomes informationally
complete with respect to the constrained set if the number of outcomes exceeds
twice the Minkowski dimension of the set. We apply the obtained results to
determine the minimal number of outcomes of measurements which are
informationally complete with respect to states with rank constraints. In
particular, we show that 4d-4 measurement outcomes (POVM elements) is enough in
order to identify all pure states in a d-dimensional Hilbert space, and that
the minimal number is at most 2 log_2(d) smaller than this upper bound.Comment: v3: There was a mistake in the derived finer upper bound in Theorem
3. The corrected upper bound is +1 to the earlier versio
Combined effect of coherent Z exchange and the hyperfine interaction in atomic PNC
The nuclear spin-dependent parity nonconserving (PNC) interaction arising
from a combination of the hyperfine interaction and the coherent,
spin-independent, PNC interaction from Z exchange is evaluated using many-body
perturbation theory. For the 6s-7s transition in 133Cs, we obtain a result that
is about 40% smaller than that found previously by Bouchiat and Piketty [Phys.
Lett. B 269, 195 (1991)]. Applying this result to 133Cs, leads to an increase
in the experimental value of nuclear anapole moment and exacerbates differences
between constraints on PNC meson coupling constants obtained from the Cs
anapole moment and those obtained from other nuclear parity violating
experiments. Nuclear spin-dependent PNC dipole matrix elements, including
contributions from the combined weak-hyperfine interaction, are also given for
the 7s-8s transition in 211Fr and for transitions between ground-state
hyperfine levels in K, Rb, Cs, Ba+, Au, Tl, Fr, and Ra+.Comment: Revtex4 preprint 19 pages 4 table
Exact Minimum Eigenvalue Distribution of an Entangled Random Pure State
A recent conjecture regarding the average of the minimum eigenvalue of the
reduced density matrix of a random complex state is proved. In fact, the full
distribution of the minimum eigenvalue is derived exactly for both the cases of
a random real and a random complex state. Our results are relevant to the
entanglement properties of eigenvectors of the orthogonal and unitary ensembles
of random matrix theory and quantum chaotic systems. They also provide a rare
exactly solvable case for the distribution of the minimum of a set of N {\em
strongly correlated} random variables for all values of N (and not just for
large N).Comment: 13 pages, 2 figures included; typos corrected; to appear in J. Stat.
Phy
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