bluuebunny/crossref_metadata_2025 huggingface dataset:
Geochemical constraints on the hydrothermal origin of ferromanganese encrustations from the Rodriguez Triple Junction, Indian Ocean
Authors: Nagender Nath B. , Plüger W. L. , Roelandts I.
Published: September 2007

Ferromanganese crusts recovered from a spreading ridge north of the Rodriguez Triple Junction in the Indian Ocean were studied for their mineral and geochemical compositions. The crusts are highly porous, have maximum thickness of 2 cm, and occur on basaltic substrates. The composition of the crusts resembles that of hydrothermal ferromanganese crusts from other oceanic spreading centres. Compared to hydrogenous ferromanganese crusts and nodules, the hydrothermal crusts exhibit very low Mn/Fe ratios, lower transitional metal contents, low ΣREE contents and negaive Ce anomalies, which are all characteristics of hydrothermal origin. Geochemical discriminant plots of crust data show similarities to data for metalliferous sediment and hydrothermal deposits recovered from other areas. Shale-normalized REE patterns indicate that the hydrothermal contribution to the crusts is between 60 and 92%. Crusts have rarely been reported to occur at Indian Ocean spreading centers, and those described here are consistent with the earlier findings on water column temperature and chemical anomalies indicative of hydrothermal activity in the region.

Some aspects of the crusts, such as
δ
-MnO
2
mineralogy and middle REE enrichment, are not typical of hydrothermal Fe-Mn oxides. Microprobe studies show that some layers within the crusts have Mn/Fe ratios close to unity, suggesting a significant input from normal seawater.

Growth rates, estimated from an algorithm based on Mn, Fe and Co contents, are orders of magnitude faster than rates determined for hydrogenous Fe-Mn oxides. The outer layers and some internal layers of the crust had relatively faster growth rates indicating that the crusts precipitated from distinct hydrothermal episodes.
Deception Island (Antarctica): a new target for exploration of Fe-Mn mineralization?
Authors: Rey J. , Somoza L. , Martínez-Frías J. , Benito R. , Martín-Alfageme S.
Published: September 2007

This work correlates the submarine volcanic and hydrothermal structures detected through seismic profiles on Deception Island (DI) with geochemical distribution patterns of the volcanic sediments which make up the seafloor of the island. A comparison of subaerial and submarine volcanic events is also carried out and three groups of submerged seismo-depositional units are defined. A model is proposed according to which the highest contents of Fe-Mn-Zn are related to volcanic cones, mounds and vents formed in relation with extensional normal low-angle faults. The As-Ba anomalies, active fumaroles and hot-springs are associated to later tensional faults.
Terrestrial hot-spring Co-rich Mn mineralization in the Pliocene-Quaternary Calatrava Region (central Spain)
Authors: Crespo A. , Lunar R.
Published: September 2007

Central Spain hosts a series of high-Co (up to 1.7% Co) Mn mineralizations displaying a variety of morphologies: spring aprons and feeders, pisolitic beds, wad beds and tufa-like replacements of plants and plant debris. The Mn mineralogy consist of cryptomelane, lithiophorite, birnessite and todorokite. The spring apron deposits formed in close proximity to Pliocene volcanic rocks (alkaline basaltic lava flows and pyroclastics) belonging to the so-called Calatrava Volcanic Field. The spring aprons are found along or near to normal faults bounding small basins and topographic highs. Mn tufa-like deposits are found near to the spring sources, while both pisolitic and wad beds are clearly distal facies occuring well within the Pliocene basins. The two latter are interbedded with clastic lacustrine and fluvial sediments. Collectively, these deposits contain a complex suite of Mn-(Co) mineralization ranging from proximal, hot-spring-type Mn facies, grading into more distant sedimentary, stratabound mineralization. Volcanism, basin formation and Mn deposition took place within a failed rift environment which triggered hydrothermal activity and Mn-(Co) deposition as proximal (near to the volcanic axes) and distal (of sedimentary affinities, within the basins) facies.
Formation of solid phases of manganese in oxygenated aquatic environments
Authors: Gramm-Osipov Lev M.
Published: September 2007

The article describes a thermodynamic analysis of the formation process of solid manganese phases in oxygenated aquatic environment. The first step of this process is the formation of the compound MnOOH. In the second step the latter in a disproportionation reaction is transformed into a complicated oxohydroxide [(MnO
2
)

2
n
−3

(MnOOH)

4−2
n

] with O/Mn ranging from 1.700 to 1.999. As an example of using results of thermodynamic analyses the behaviour Mn system in the ocean is described. It is shown that Mn
3
O
4
and MnOOH respectively control concentrations and distribution of the manganese in the upper (150–600 m) and lower oceanic water column.
P-T-X relationships during metamorphism of manganese-rich sediments: Current status and future studies
Authors: Dasgupta Somnath
Published: September 2007

This paper aims at reviewing the mineralogy, mineral chemistry and petrology of metamorphosed manganese-rich sediments from occurrences described since 1988. It presents a summary of new experimental data and evaluates the merits and shortcomings of the petrogenetic grids so far proposed for Mn-rich metamorphic rocks. The paper focuses on the inadequacies of experimental data on Mn-rich systems and discusses the problems associated with further quantification of the petrogenetic grids. Finally, a few suggestions for future research on Mn-rich systems are put forward.
Zincian rancieite from the Kato Nevrokopi manganese deposits, Macedonia, northern Greece
Authors: Nimfopoulos M. K. , Michailidis K. M. , Christofides G.
Published: September 2007

At the 25th km main Mn-mine of Kato Nevrokopi, Macedonia, northern Greece, rancieite forms flaky to laminated aggregates encrusting vugs, and replacing pyrolusite and todorokite in massive deposits of the Falakron marbles. It has an unusually high ZnO (1.53–3.07 wt%) content and therefore it was named ‘zincian rancieite’. The average (18 spots) chemical composition of rancieite by EPMA is (wt%): MnO
2
62.01, CaO 6.83, ZnO 2.54, Al
2
O
3
1.18, MgO 0.63 plus minor oxides (Fe
2
O
3
, K
2
O & SiO
2
), total of 73.98. Assuming H
2
O-content as 26.02 (100 − 73.98) wt%, these data reflect the following empirical formula: (Ca
0.67
Zn
0.17
Al
0.12
Mg
0.09
Fe
0.02
3
K
0.02
Si
0.02
)Mn
3.90
4
O
9
7.9H
2
O. A high H
2
O-content is also evidenced by the XRD pattern, which together with optical microscopy and SEM, indicates a poor structural order. Rancieite formation at Kato Nevrokopi belongs to the last stage of mineral genesis, which took place at ambient P, low T (around 25°C) by percolating oxygen bearing, Ca-Zn rich, meteoric water through the host marble.
A non-contacting resistivity imaging method for characterizing whole round core while in its liner
Authors: Jackson P. D. , Gunn D. G. , Flint R. C. , Beamish D. , Meldrum P. I. , Lovell M. A. , Harvey P. K. , Peyton A.
Published: September 2007

Recent laboratory experimentation has shown that non-contacting whole-core resistivity imaging, with azimuthal discrimination, is feasible. It has shown the need for very sensitive coil pairs in order to provide resistivity measurements at the desired resolution. Independent high-resolution ‘galvanic’ resistivity estimations show the ‘non-contacting’ measurements to be directly proportional to the resistivity of core samples. The response of the technique to a variety of synthetic ‘structures’ is presented. A whole-core image of a dipping layer is used to demonstrate the three dimensional response of the technique and to show that the resolution of the measurements is of the order of 10 mm.

Experiments are described which show that the technique is capable of investigating to different depths within the whole round core. The results agree with theoretical predictions and indicate that the technique has the potential to assess invasion near the surface of the core.

The technique is intrinsically safe and has the potential to be packaged in a form that would be suitable for whole-core imaging at the well site, or laboratory, without taking core from their liners. Thus it is possible to acquire information crucial for core selection, in addition to acquiring resistivity data at a resolution not too far removed from that of the downhole imaging tools.
Network analogues of wettability at the pore scale
Authors: McDougall S. R. , Dixit A. B. , Sorbie K. S.
Published: September 2007

This paper examines the macroscopic consequences of wettability variations at the pore scale. Important theoretical issues relating to distributed contact angles are examined and a process simulator capable of simulating the full flooding cycle characteristic of laboratory wettability tests is described. Simulations predict that final waterflood recoveries from weakly water wet (or even weakly oil wet) systems can often exceed those from strongly water-wet systems (even though initial imbibition rates may lead to the opposite conclusion). The underlying pore level physics has been explored by defining a capillarity surface, which incorporates the combined effects of both contact angle and pore dimension during the imbibition process. Finally, a regime-based framework has been developed which may go some way towards reconciling apparently contradictory wettability experiments.
Pore-structure visualization in microdioritic enclaves
Authors: Pugliese S. , Petford N.
Published: September 2007

We present a simple methodology for estimating key petrophysical characteristics of partially molten (igneous) porous media using microgranular (microdiritic) enclaves from the Ross of Mull granite, Scotland, as examples. A number of enclaves have been infiltrated by granitic melt while still partially molten, with the infiltration (porosity) network now preserved as frozen-in granitic melt. By serial sectioning through individual enclaves, we show that the preserved infiltration channel network is interconnected in three dimensions. Using image analysis techniques, we have estirnated the porosity (
φ
) of individual enclave sections and obtained the variation in porosity with depth. Simple representation of the pore-channel network on a branch and node chart allows useful petrophysical characteristics including the connectivity, genus and tortuosity of the network to be estimated. Computer-enhanced reconstructions of the pore network in three dimensions are shown that provide a powerful way of visualizing complex geometries in porous media.
Pore-size data in petrophysics: a perspective on the measurement of pore geometry
Authors: Basan Paul B. , Lowden Ben D. , Whattler Peter R. , Attard John J.
Published: September 2007

Mercury injection capillary pressure (MICP), backscattered electron images (BSEI) and nuclear magnetic resonance (NMR) provide pore-geometry parameters useful for understanding variations in rock properties. MICP pore size is an area-equivalent diameter of the throats connecting the pore system. The MICP distribution contains a point (the turning point) that reveals where mercury first encounters the permeable network. This point identifies both critical pore size and connected porosity. BSEI measure pore area and diameter. Both parameters are unrelated to any specific morphological element. NMR pore size is a derivative of the pore-surface:volume ratio. Like BSEI, NMR pore size is unrelated to morphological elements. Like MICP, NMR provides a pore-size distribution that represents the entire sample volume.

All three techniques provide a data distribution suitable for cross-correlation. Matching distributions determines the character of the permeable pore system. NMR and MICP distributions compare through the entire time and pressure spectra, matching best in the central part of the distributions. The match suggests pore-throats merge with the pore channels in the permeable part of the system. BSEI distributions match only with the low-pressure, slow-time parts of the other distributions. However, image porosity has a stronger correlation with permeability than any of the other parameters, suggesting that the BSEI distribution is near the turning point.
Measurements of the relationship between Sonic wave velocities and tensile strength in Anisotropic rock
Authors: Apuani T. , King M. S. , Butenuth C. , De Freitas M. H.
Published: September 2007

This work investigates relationships between the mechanical behaviour under tension of a building stone widely used in Italy and the compressional and shear-wave velocities within the stone. The stone investigated is the Antigorio orthogneiss, which is characterized by an orthotropic petrographical anisotropy.

This rock was sampled in three orthogonal directions two of which lie in the plane of schistosity, the first parallel and the second perpendicular to the elongated structures in that plane, with the third sampling direction oriented normal to the plane of schistosity. In these directions rock cylinders were cored co-axially to provide hollow cylinders of 14cm outer diameter together with their inner solid cores of approximatly 5 cm diameter. These inner cores were used for ultrasonic wave velocity measurements (
V
p
and polarized
V
5
) oriented at 90° to the core axis, and conducted at intervals around their circumference so as to obtain wave velocities through the gneiss in different orientations. The hollow cylinders were cut into hoops and tested by the hoop tension test to provide measurements of tensile strength in the same directions as those in which wave velocities had been measured. Thus nondestructive velocity tests and destructive tensile tests were conducted in the same orientations. The paper describes the results so obtained using dry samples.
Prediction of petrophysical properties from seismic quality factor measurements
Authors: McCann C. , Sothcott J. , Assefa S. B.
Published: September 2007

Over the past eight years the Geophysics Group of the Postgraduate Research Institute for Sedimentology has developed equipment for accurately measuring the seismic properties of centimetre-size samples of sedimentary rocks at ultrasonic frequencies (0.5–1 MHz) and under simulated
in situ
conditions. Relationships between the ultrasonic properties and the mineralogical/petrophysical properties of a wide range of rock types have been investigated. The results indicate that the attenuation of seismic waves at high frequencies is dominated by the ‘imperfections’ in the rock, defined in a broad way. For instance, at low pressures the attenuation depends on the volume concentration of microcracks; at high confining pressures the attenuation depends on the distribution of porosity between the macro inter-particle porosity and the micro intra-clay or intra-particle porosity. For some rocks, analysis of these relationships leads to the ability to predict petrophysical properties, including the permeability, from the seismic data. Techniques for up-scaling the relationships to the wavelengths of field seismic surveys are discussed.
Estimation of aspect-ratio changes with pressure from seismic velocities
Authors: Sun Y. F. , Goldberg D.
Published: September 2007

Seismic velocities are modeled as a function of rock mineralogy, porosity, fracture density, aspect ratio and fluid saturation. We compare the model with seismic velocity measurements made by Nur and Simmons in 1969 and predict quantitative aspect ratio changes as a function of differential pressure. The velocity change with pressure is initially caused by the deformation and collapse of pre-existing cracks and pores followed by the initiation of new cracks. For low porosity Casco granite (0.25% pore and 0.45% crack), we estimate that crack aspect ratio increases from 5.9
e
−3
to 0.01, then decreases to 5.0
e
−5
for a pressure increase from 0 to 300 MPa. Most pre-existing cracks and pores close at differential pressures < 40MPa, a lower pressure than predicted with standard approximations. These model results can be used to determine
in situ
porosity, fluid content, and pore pressure from seismic data by inversion and for reservoir monitoring from drilling and core data.
Petrophysical estimation of permeability as a function of scale
Authors: Worthington Paul F.
Published: September 2007

The prediction of reservoir intergranular permeability from core and log measurements of other physical properties is demonstrably refined by taking a more scientific account of the scale of the predictors. Further, the expression of an empirical algorithm that relates permeability to a measured predictor can vary significantly from the core through the log to the well-test scales, with a reduction in data scatter as scale increases. In the most common case of porosity-permeability relationships, the coefficients and exponents that define the petrophysical algorithms are themselves functions of scale. The axial scale dependence of these predictive algorithms is quantified through filtering of regularly sampled core data for the specific case of primary flow and for four different distributions of characterized strata. The algorithms initially diverge as the scale of the processed data increases beyond the spatial resolution of the input core measurements, and they reconverge as the running means become more generally representative. The alternative method of predicting intergranular permeability from measurements of apparent formation factor also shows a scale dependence, which here is quantified through porosity-governed averaging of irregularly sampled core data. The algorithm so generated shows encouraging agreement with that established from a correlation of permeability inferred from drawdown tests with field-measured apparent formation factor, normalized to a reference water resistivity. The procedures used to investigate the scale dependence of petrophysical relationships are applicable to all primary clastic reservoirs that require to be characterized at the flow unit scale. They offer a
modus operandi
for establishing a fit-for-purpose, scale-reconciled relationship between permeability and a selected petrophysical predictor for a given reservoir situation. This approach should therefore lead to more reliable estimates of field permeability for input to reservoir simulation.
Prediction of petrophysical parameter logs using a multilayer backpropagation neural network
Authors: Gonçalves C. A. , Harvey P. K. , Lovell M. A.
Published: September 2007

Quantitative petrophysical characterization is one of the principal tasks of a reservoir analyst and is generally affected by the methods used. For example, different theoretical and empirical formulas are in most cases restricted to the specific areas where they were developed. Prediction of continuous petrophysical parameters is often time consuming and complicated because of geological variability such as facies changes due to sedimentary and structural changes.

In this work we propose a neural network approach which is used to predict quantitative petrophysical parameters from wireline logs of cored intervals. We then apply the knowledge learned during training to uncored intervals or other holes. Data from the Ocean Drilling Program and from two South American oilfield holes are used to test this technique.

The results show a good match between the neural network-derived petrophysical parameter logs and the actual core measurements. Problematic petrophysical measurements can be identified by a mismatch between the responses.
Electrical conductivity, spontaneous potential and ionic diffusion in porous media
Authors: Revil A. , Pezard P. A. , Darot M.
Published: September 2007

A consistent set of equations describing electrical conduction, spontaneous potential and ionic diffusion phenomena in porous media, with a particular emphasis given to surface electrical phenomena, is presented. The porous medium is assumed to consist of an insulating matrix and an inter-connected pore volume that is saturated with an electrolyte. When in contact with an electrolyte solution, mineral surfaces have an excess of charge that is balanced by mobile ions in an electrical diffuse layer (EDL). Electrical conduction and ionic diffusion in this diffuse layer can contribute substantially to the effective electrical conductivity of the porous medium, and can play an important role in the strength of several spontaneous electrical potentials (i.e., membrane potential, streaming potential, and thermo-electric potential) and ionic diffusion phenomena. Our surface electrical properties model is based on a thermodynamic description of surface chemical reactions and electrical diffuse layer processes. As an example, we consider an amphoteric mineral surface described by a three-site-type model. We derive the fractional occupancies of positive, negative and neutral sites, and the fractional ionic diffuse layer densities on the surface as a function of the salinity and the pH. The surface charge density at a given pH, is found to be dependent on the electrolyte concentration. Finally, parameters of interest in describing macroscopic effects (effective electrical conductivity, spontaneous potential coupling coefficients and effective diffusion coefficient), are related to the previously mentioned properties, via the mineral surface electrical potential (called the Stern potential).
Fractal Geometry, porosity and complex resistivity: from hand specimen to field data
Authors: Da Rocha Brígida Ramati P. , Habashy Tarek M.
Published: September 2007

In the induced polarization (IP) method of geophysical prospecting, the frequency dependence of the constitutive parameters (conductivity and permittivity) of rocks is exploited to distinguish between different types of rocks with different types of mineralization. Unavoidably, the field data measured using either a four electrode array or an inductive type setup employing ungrounded loops will not directly provide the induced polarization properties of the geological medium to the exclusion of the ‘electromagnetic coupling’. In fact one can not measure one effect without the other. Inference of the medium constitutive parameters from field data is often masked and confused by the purely electromagnetic effects that would be present even when the medium is non-dispersive.

In this paper we present a framework by which one can separate the electrochemical effects from the electromagnetic effects which are usually intertwined in a complicated manner in the measured field data. We formulate the problem in a fairly general way without introducing the customary quasi-static approximation. The model we use is that of a layered earth with one of the layers representing a polarizable medium and the rest of the layers are non-polarizable. The effective complex resistivity of the polarizable medium, which is described in a companion paper, is given by a generalized Cole-Cole type resistive network.
Tortuosity: a guide through the maze
Authors: Clennell M. Ben
Published: September 2007

Despite its widespread use in petrophysics, tortuosity remains a poorly understood concept. Tortuosity can have various meanings when used by physicists, engineers or geologists to describe different transport processes taking place in a porous material. Values for geometrical, electrical, diffusional and hydraulic tortuosity are in general different from one another. Electrical tortuosity is defined in terms of conductivity whereas hydraulic tortuosity is usually defined geometrically, and diffusional tortuosity is typically computed from temporal changes in concentration. A better approach may be to define tortuosity in terms of the underlying flux of material or electrical current with respect to the forces which drive this flow.

Unsteady transport processes, including diffusion, can be described only by a population of tortuosities corresponding to the different flow paths taken by particles traversing the medium. In measurements of steady flow (e.g., those normally used to obtain resistivity or permeability), information about particle travel times is lost, and so the multiple values of tortuosity are homogenised. It can be shown that the maximum amount of information about pore structure is embedded in transport processes that combine advective and diffusive elements.

Most existing formulations of tortuosity are model-dependent, and cannot be correlated with independently measurable pore-structure properties. Nevertheless, tortuosity underpins the rigorous relationships between transport processes in rocks, and ties them with the underlying geometry and topology of their pore spaces. Tortuosity can be redefined in terms of the energetic efficiency of a flow process. The efficiency is related to the rate of entropy dissipation (or isothermally, energy dissipation) with respect to a simple, non-tortuous model medium using the postulates of non-equilibrium thermodynamics. Through Onsager’s reciprocity relation for coupled flows it is possible to inter-relate efficiency for pairs of transport processes, and so go some way towards unifying tortuosity measures. In this way we can approach the goal of predicting the value of one transport parameter from measurements of another.
Scattering attenuation as a function of depth in the Upper Oceanic Crust
Authors: Goldberg D. , Sun Y. F.
Published: September 2007

The
in situ
attenuation is computed through 2.1 km of the upper oceanic crust in the vicinity of ODP Hole 504B on the southflank of the Costa Rica Rift in the eastern equatorial Pacific. The results strongly tie crustal properties to seismic measurables and observed geological structures: we find that the attenuation can be used to define seismic layer boundaries and is closely related to vertical heterogeneity. The
in situ
attenuation
Q
−1
consists of both intrinsic and scattering contributions, but is dominated by the scattering attenuation unless porosities are near zero, when it approaches typical estimates from seismic refraction studies. The attenuation is analytically modeled by multiple backscattering from heterogeneities observed in a sonic
V
p
log and is found to decrease step-wise from
Q
= 25 to
Q
> 300 between the top of seismic layer 2A and a sharp discontinuity at 1.3 km depth. These changes correspond with heterogeneities at 1.0–1.3 m and at 10.0 m wavelengths that are associated with fracturing and the structure of pillow basalts and lava flows in seismic layers 2A and 2B. Although seismic velocity studies suggest that the layer 2–3 boundary also occurs at about 1.3 km, the large variation in
Q
(140 to 460) below this depth indicates that a seismically homogeneous layer 3 has not been reached in Hole 504B. From the observed results, we derive an empirical relationship between attenuation and porosity
Q
−1
=
Q
0
−1
e
βφ
, where
Q
0
−1
= 0.004, β= 25, that may be applicable at other oceanic crust locations and useful for constraining seismic inversion models.
The PCP theorem by gap amplification
Authors: Dinur Irit
Published: September 2007

The PCP theorem [Arora and Safra 1998; Arora et. al. 1998] says that every language in NP has a witness format that can be checked probabilistically by reading only a constant number of bits from the proof. The celebrated equivalence of this theorem and inapproximability of certain optimization problems, due to Feige et al. [1996], has placed the PCP theorem at the heart of the area of inapproximability.

In this work, we present a new proof of the PCP theorem that draws on this equivalence. We give a combinatorial proof for the NP-hardness of approximating a certain constraint satisfaction problem, which can then be reinterpreted to yield the PCP theorem.

Our approach is to consider the
unsat value
of a constraint system, which is the smallest fraction of unsatisfied constraints, ranging over all possible assignments for the underlying variables. We describe a new combinatorial amplification transformation that doubles the unsat-value of a constraint-system, with only a linear blowup in the size of the system. The amplification step causes an increase in alphabet-size that is corrected by a (standard) PCP composition step. Iterative application of these two steps yields a proof for the PCP theorem.

The amplification lemma relies on a new notion of “graph powering” that can be applied to systems of binary constraints. This powering amplifies the unsat-value of a constraint system provided that the underlying graph structure is an expander.

We also extend our amplification lemma towards construction of assignment testers (alternatively, PCPs of Proximity) which are slightly stronger objects than PCPs. We then construct PCPs and locally-testable codes whose length is linear up to a
polylog
factor, and whose correctness can be probabilistically verified by making a
constant
number of queries. Namely, we prove
SAT
∈
PCP
1/2,1
[log
2
(
n
⋅poly log
n
),
O
(1)].
Characterizing and reasoning about probabilistic and non-probabilistic expectation
Authors: Halpern Joseph Y. , Pucella Riccardo
Published: September 2007

Expectation is a central notion in probability theory. The notion of expectation also makes sense for other notions of uncertainty. We introduce a propositional logic for reasoning about expectation, where the semantics depends on the underlying representation of uncertainty. We give sound and complete axiomatizations for the logic in the case that the underlying representation is (a) probability, (b) sets of probability measures, (c) belief functions, and (d) possibility measures. We show that this logic is more expressive than the corresponding logic for reasoning about likelihood in the case of sets of probability measures, but equi-expressive in the case of probability, belief, and possibility. Finally, we show that satisfiability for these logics is NP-complete, no harder than satisfiability for propositional logic.
SIPs
Authors: Zhang Hong , Smith Barry , Sternberg Michael , Zapol Peter
Published: September 2007

SIPs is a new efficient and robust software package implementing multiple shift-and-invert spectral transformations on parallel computers. Built on top of SLEPc and PETSc, it can compute very large numbers of eigenpairs for sparse symmetric generalized eigenvalue problems. The development of SIPs is motivated by applications in nanoscale materials modeling, in which the growing size of the matrices and the pathological eigenvalue distribution challenge the efficiency and robustness of the solver. In this article, we present a parallel eigenvalue algorithm based on distributed spectrum slicing. We describe the object-oriented design and implementation techniques in SIPs, and demonstrate its numerical performance on an advanced distributed computer.
Using the GA and TAO toolkits for solving large-scale optimization problems on parallel computers
Authors: Benson Steven , Krishnan Manojkumar , Mcinnes Lois , Nieplocha Jarek , Sarich Jason
Published: September 2007

Challenges in the scalable solution of large-scale optimization problems include the development of innovative algorithms and efficient tools for parallel data manipulation. This article discusses two complementary toolkits from the collection of Advanced CompuTational Software (ACTS), namely, Global Arrays (GA) for parallel data management and the Toolkit for Advanced Optimization (TAO), which have been integrated to support large-scale scientific applications of unconstrained and bound constrained minimization problems. Most likely to benefit are minimization problems arising in classical molecular dynamics, free energy simulations, and other applications where the coupling among variables requires dense data structures. TAO uses abstractions for vectors and matrices so that its optimization algorithms can easily interface to distributed data management and linear algebra capabilities implemented in the GA library. The GA/TAO interfaces are available both in the traditional library mode and as components compliant with the Common Component Architecture (CCA). We highlight the design of each toolkit, describe the interfaces between them, and demonstrate their use.
OPT++
Authors: Meza J. C. , Oliva R. A. , Hough P. D. , Williams P. J.
Published: September 2007

Object-oriented programming is a relatively new tool in the development of optimization software. The code extensibility and the rapid algorithm prototyping capability enabled by this programming paradigm promise to enhance the reliability, utility, and ease of use of optimization software. While the use of object-oriented programming is growing, there are still few examples of general purpose codes written in this manner, and a common approach is far from obvious. This paper describes OPT++, a C++ class library for nonlinear optimization. The design is predicated on the concept of distinguishing between an algorithm-independent class hierarchy for nonlinear optimization problems and a class hierarchy for nonlinear optimization methods that is based on common algorithmic traits. The interface is designed for ease of use while being general enough so that new optimization algorithms can be added easily to the existing framework. A number of nonlinear optimization algorithms have been implemented in OPT++ and are accessible through this interface. Furthermore, example applications demonstrate the simplicity of the interface as well as the advantages of a common interface in comparing multiple algorithms.
MPFR
Authors: Fousse Laurent , Hanrot Guillaume , Lefèvre Vincent , Pélissier Patrick , Zimmermann Paul
Published: September 2007

This article presents a multiple-precision binary floating-point library, written in the ISO C language, and based on the GNU MP library. Its particularity is to extend to arbitrary-precision, ideas from the IEEE 754 standard, by providing
correct rounding
and
exceptions
. We demonstrate how these strong semantics are achieved---with no significant slowdown with respect to other arbitrary-precision tools---and discuss a few applications where such a library can be useful.
Algorithm 866
Authors: Elman Howard C. , Ramage Alison , Silvester David J.
Published: September 2007

IFISS is a graphical Matlab package for the interactive numerical study of incompressible flow problems. It includes algorithms for discretization by mixed finite element methods and a posteriori error estimation of the computed solutions. The package can also be used as a computational laboratory for experimenting with state-of-the-art preconditioned iterative solvers for the discrete linear equation systems that arise in incompressible flow modelling. A unique feature of the package is its comprehensive nature; for each problem addressed, it enables the study of both discretization and iterative solution algorithms as well as the interaction between the two and the resulting effect on overall efficiency.
Remark on algorithm 515
Authors: Crouse David F.
Published: September 2007

We present a correction to Algorithm 515 [Buckles and Lybanon 1977].
Efficient sampling of training set in large and noisy multimedia data
Authors: Wang Surong , Dash Manoranjan , Chia Liang-Tien , Xu Min
Published: September 2007

As the amount of multimedia data is increasing day-by-day thanks to less expensive storage devices and increasing numbers of information sources, machine learning algorithms are faced with large-sized and noisy datasets. Fortunately, the use of a good sampling set for training influences the final results significantly. But using a simple random sample (SRS) may not obtain satisfactory results because such a sample may not adequately represent the large and noisy dataset due to its blind approach in selecting samples. The difficulty is particularly apparent for huge datasets where, due to memory constraints, only very small sample sizes are used. This is typically the case for multimedia applications, where data size is usually very large. In this article we propose a new and efficient method to sample of large and noisy multimedia data. The proposed method is based on a simple distance measure that compares the histograms of the sample set and the whole set in order to estimate the representativeness of the sample. The proposed method deals with noise in an elegant manner which SRS and other methods are not able to deal with. We experiment on image and audio datasets. Comparison with SRS and other methods shows that the proposed method is vastly superior in terms of sample representativeness, particularly for small sample sizes although time-wise it is comparable to SRS, the least expensive method in terms of time.
Critical causal order of events in distributed virtual environments
Authors: Zhou Suiping , Cai Wentong , Turner Stephen J. , Lee Bu-Sung , Wei Junhu
Published: September 2007

We investigate the causal order of events in distributed virtual environments (DVEs). We first define the critical causal order relation among the events. Then, we propose some mechanisms to enhance the prevalent RO (receive order delivery) mechanism in DVEs so that the real-time property of DVEs is preserved while the critical causal order violations are reduced. These mechanisms are implemented as a middleware. Experimental results show that the middleware performs well in reducing the critical causality violations in simulation and incurs little processing overhead.
Segmentation and recognition of motion streams by similarity search
Authors: Li Chuanjun , Zheng S. Q. , Prabhakaran B.
Published: September 2007

Fast and accurate recognition of motion data streams from gesture sensing and motion capture devices has many applications and is the focus of this article. Based on the analysis of the geometric structures revealed by singular value decompositions (SVD) of motion data, a similarity measure is proposed for simultaneously segmenting and recognizing motion streams. A direction identification approach is explored to further differentiate motions with similar data geometric structures. Experiments show that the proposed similarity measure can segment and recognize motion streams of variable lengths with high accuracy, without knowing beforehand the number of motions in a stream.
An open architecture for transport-level protocol coordination in distributed multimedia applications
Authors: Ott David E. , Mayer-Patel Ketan
Published: September 2007

We consider the problem of flow coordination in distributed multimedia applications. Most transport-level protocols are designed to operate independently and lack mechanisms for sharing information with other flows and coordinating data transport in various ways. This limitation becomes problematic in distributed applications that employ numerous flows between two computing clusters sharing the same intermediary forwarding path across the Internet. In this article, we propose an open architecture that supports the sharing of network state information, peer flow information, and application-specific information. Called simply the
coordination protocol (CP)
, the scheme facilitates coordination of network resource usage across flows belonging to the same application, as well as aiding other types of coordination. The effectiveness of our approach is illustrated in the context of multistreaming in 3D tele-immersion where consistency of network information across flows both greatly improves frame transport synchrony and minimizes buffering delay.
Robust content-based MPEG-4 XMT scene structure authentication and multimedia content location
Authors: Sakr Ziad , Georganas Nicolas D.
Published: September 2007

For the past decade, there have been numerous research works focusing on the protection of digital images, audio, video, 3D virtual scenes, and software data from unauthorized use and distribution. With the emerging technology of the MPEG-4 standard, MPEG-4 scenes that may include images, video, audio, and 3D objects can easily be built using the text-based MPEG-4 XMT standard. XMT allows content authors to exchange their content with other authors, tools, or service providers and facilitates interoperability with MPEG-4, X3D, and SMIL. In order for owners and designers to protect and/or authenticate their work, some form of security needs to be applied into the MPEG-4 XMT structure and its media content. Unlike images or videos, watermarking an XMT structure is not an easy task, since the structure contains no noise components to embed the watermark. This article is the first one proposing a novel robust algorithm for the authentication of a given MPEG-4 XMT structured scene and the location of its multimedia content.
Bounds on coverage and target detection capabilities for models of networks of mobile sensors
Authors: Brass Peter
Published: September 2007

In this article we analyze the capabilities of various models of sensor networks with the Boolean sensing model for mobile or stationary sensors and targets, under random or optimal placement, independent or globally coordinated search, and stealthy or visible sensors. For each model we give an upper bound for the capabilities under any strategy, and a search strategy which at least asymptotically matches that bound. To ensure comparability of these models, we present them using the same parameters: the sensing radius
r
, sensor placement density λ, as well as the travel distance
l
of each sensor and
d
of the target. By this we obtain a complete analysis of the geometric coverage and detection capabilities of the various models of sensor networks, where we abstract from issues like communication and power management.
A diffusion model for packet travel time in a random multihop medium
Authors: Gelenbe Erol
Published: September 2007

We consider a wireless network in which packets are forwarded opportunistically from the source towards the destination, without accurate knowledge of the direction that they should take. A Brownian motion model that includes the effect of packet losses, and subsequent retransmission after a time-out, is used to compute the average travel time of the packet. The results indicate that the average travel time is always finite provided that a time-out is used, and that there is an element of randomness in the manner in which successive nodes are being chosen. We show that the average packet travel time can be minimized by a judicious choice of the time-out, and its optimum value in turn depends on other system parameters such as packet-loss probabilities. We present simulations that illustrate the analytical results.
Coverage breach problems in bandwidth-constrained sensor networks
Authors: Cheng Maggie X. , Ruan Lu , Wu Weili
Published: September 2007

Recent research in sensor networks highlights the low-power mode operation of sensor networks. In wireless sensor networks, network lifetime can be extended by organizing sensors into mutually exclusive subsets and alternatively activating each subset. Coverage breach occurs when a subset fails to cover all the targets. In bandwidth-constrained sensor networks, coverage breach is more likely to happen because when active sensors periodically send data to the base station, contention for channel access must be considered. Channel bandwidth imposes a limit on the cardinality of each subset. To make efficient use of both energy and bandwidth with minimum coverage breach requires optimal arrangement of sensor nodes.

This article addresses three coverage breach problems related to the low-power operation of wireless sensor networks where channel bandwidth is limited. The three coverage breach problems are formulated using integer linear programming models. A greedy approximation algorithm and a heuristic based on the LP-relaxation method are proposed. Effects of changing different network resources on sensor network coverage are studied through simulations. One consistent result is that when the number of sensors increases, network lifetime can be improved without loss of network coverage only if there is no bandwidth constraint; with bandwidth constraints, network lifetime may be improved further at the cost of coverage breach.
A taxonomy of suffix array construction algorithms
Authors: Puglisi Simon J. , Smyth W. F. , Turpin Andrew H.
Published: September 2007

In 1990, Manber and Myers proposed suffix arrays as a space-saving alternative to suffix trees and described the first algorithms for suffix array construction and use. Since that time, and especially in the last few years, suffix array construction algorithms have proliferated in bewildering abundance. This survey paper attempts to provide simple high-level descriptions of these numerous algorithms that highlight both their distinctive features and their commonalities, while avoiding as much as possible the complexities of implementation details. New hybrid algorithms are also described. We provide comparisons of the algorithms' worst-case time complexity and use of additional space, together with results of recent experimental test runs on many of their implementations.
A survey of RST invariant image watermarking algorithms
Authors: Zheng Dong , Liu Yan , Zhao Jiying , Saddik Abdulmotaleb El
Published: September 2007

In this article, we review the algorithms for rotation, scaling and translation (RST) invariant image watermarking. There are mainly two categories of RST invariant image watermarking algorithms. One is to rectify the RST transformed image before conducting watermark detection. Another is to embed and detect watermark in an RST invariant or semi-invariant domain. In order to help readers understand, we first introduce the fundamental theories and techniques used in the existing RST invariant image watermarking algorithms. Then, we discuss in detail the work principles, embedding process, and detection process of the typical RST invariant image watermarking algorithms. Finally, we analyze and evaluate these typical algorithms through implementation, and point out their advantages and disadvantages.
Query-sensitive embeddings
Authors: Athitsos Vassilis , Hadjieleftheriou Marios , Kollios George , Sclaroff Stan
Published: September 2007

A common problem in many types of databases is retrieving the most similar matches to a query object. Finding these matches in a large database can be too slow to be practical, especially in domains where objects are compared using computationally expensive similarity (or distance) measures. Embedding methods can significantly speed-up retrieval by mapping objects into a vector space, where distances can be measured rapidly using a Minkowski metric. In this article we present a novel way to improve embedding quality. In particular, we propose to construct embeddings that use a
query-sensitive
distance measure for the target space of the embedding. This distance measure is used to compare those vectors that the query and database objects are mapped to. The term “query-sensitive” means that the distance measure changes, depending on the current query object. We demonstrate theoretically that using a query-sensitive distance measure increases the modeling power of embeddings and allows them to capture more of the structure of the original space. We also demonstrate experimentally that query-sensitive embeddings can significantly improve retrieval performance. In experiments with an image database of handwritten digits and a time-series database, the proposed method outperforms existing state-of-the-art non-Euclidean indexing methods, meaning that it provides significantly better tradeoffs between efficiency and retrieval accuracy.