bluuebunny/crossref_metadata_2025 huggingface dataset:
EFFECTIVE FIELD THEORY OF A LOCALLY NONCOMMUTATIVE SPACE–TIME AND EXTRA DIMENSIONS
Authors: MIRZA B. , ZAREI M.
Published: July 2008

We assume that the noncommutativity starts to be visible continuously from a scale ΛNC. According to this assumption, a two-loop effective action is derived for noncommutative ϕ4 and ϕ3 theories from a Wilsonian point of view. We show that these effective theories are free of UV/IR mixing phenomena. We also investigate the positivity constraint on coefficients of higher dimension operators present in the effective theory. This constraint makes the low energy theory to be UV completion of a full theory. Finally, we discuss noncommutativity and extra dimensions. In our effective theories formulated on noncommutative extra dimensions, if the campactification scale Λc is less than the scale ΛNC, the theory will not suffer from UV/IR mixing.
STRUCTURE OF INITIAL PROTOPLANETS
Authors: PAUL G. C. , PRAMANIK J. N. , BHATTACHARJEE S. K.
Published: July 2008

The structure of a protoplanet has been determined by numerical method in which the protoplanet is assumed to be a gaseous sphere of solar composition having Jovian mass, which is in a steady state of quasistatic equilibrium. It is also assumed that the only source of energy in a protoplanet is gravitational. Regarding the transference of heat inside the protoplanet, we have considered two cases of interest (i) the convective case and (ii) the conductive–radiative case. It is found that in both cases the system possesses unique solution.
QUASINORMAL MODES AND LATE-TIME TAILS IN THE BACKGROUND OF SCHWARZSCHILD BLACK HOLE PIERCED BY A COSMIC STRING: SCALAR, ELECTROMAGNETIC AND GRAVITATIONAL PERTURBATIONS
Authors: CHEN SONGBAI , WANG BIN , SU RUKENG
Published: July 2008

We have studied the quasinormal modes and the late-time tail behaviors of scalar, electromagnetic and gravitational perturbations in the Schwarzschild black hole pierced by a cosmic string. Although the metric is locally identical to that of the Schwarzschild black hole so that the presence of the string will not imprint in the motion of test particles, we found that quasinormal modes and the late-time tails can reflect physical signatures of the cosmic string. Compared with the scalar and electromagnetic fields, the gravitational perturbation decays slower, which would be more interesting to disclose the string effect in this background.
TRACE FORMULA FOR GREEN'S FUNCTIONS OF EFFECTIVE MASS SCHRÖDINGER EQUATIONS AND NTH-ORDER DARBOUX TRANSFORMATIONS
Authors: POZDEEVA EKATERINA , SCHULZE-HALBERG AXEL
Published: July 2008

We derive a trace formula for Green's functions of position-dependent (effective) mass Schrödinger equations that are defined on a real, finite interval and connected by a Darboux transformation of arbitrary order. Our findings generalize former results (J. Phys. A37, 10287 (2004)) on constant mass Schrödinger equations to the effective mass case.
EFFECT OF NANO Ag ADDITION ON THE SUPERCONDUCTING AND TRANSPORT PROPERTIES OF YBa2Cu3O7-δ PREPARED BY SOL-GEL ROUTE
Authors: YEOH L. M. , AHMAD M. , ABD-SHUKOR R.
Published: July 2008

The effect of nano size Ag addition on the YBa 2 Cu 3 O 7-δ (Y-123) system has been investigated. 2–15% weight of nano size Ag was added to the Y-123 system prepared by using the sol-gel-solid-state method. The phase purity was investigated by the powder X-ray diffraction method. Energy Dispersive X-ray Analysis (EDAX) was used to determine the distribution of nano Ag in the samples, and the microstructure was observed using a Scanning Electron Microscope (SEM). The transport critical current density was found to increase with increase in nano Ag content.
MOLECULAR DYNAMICS SIMULATION OF RAPID SOLIDIFICATION OF ALUMINUM UNDER PRESSURE
Authors: SARKAR A. , BARAT P. , MUKHERJEE P.
Published: July 2008

Molecular dynamics simulation study based on the EAM potential is carried out to investigate the effect of pressure on the rapid solidification of Aluminum. The radial distribution function is used to characterize the structure of the Al solidified under different pressures. It is indicated that a high pressure leads to strong crystallization tendency during cooling.
A NEW HIGHER-DIMENSIONAL LOOP ALGEBRA AND ITS APPLICATION
Authors: XU XIULI , GONG XINBO , ZHANG YUFENG , SONG MING
Published: July 2008

With the help of the cycled numbers, a higher-dimensional loop algebra is constructed, whose dimension is 4(s+1). For computing convenience, we only take s = 1 as an example. By employing loop algebra [Formula: see text], a generalized Toda hierarchy is obtained with possessing two-Hamiltonian structure, which is also reduced to the well-known Toda hierarchy.
ENHANCING OWL ONTOLOGIES WITH RELATION SEMANTICS
Authors: KOTHARI CARTIK R. , RUSSOMANNO DAVID J.
Published: July 2008

The OWL Enhance prototype has been developed to augment ontologies implemented using the Web Ontology Language (OWL) with richer relation semantics. This prototype interactively elicits knowledge from providers to describe the intrinsic nature of relations and appends these elicited semantics to definitions of relations in OWL ontologies. Benefits from the explicit specification of the intrinsic nature of relations in ontologies include the development of quantitative techniques for the estimation of similarities among relations and attribute exploration techniques to create relation taxonomies. Examples of these techniques have been implemented in modules of the OWL Enhance prototype to demonstrate the utility of explicit relation semantics. Results from testing these modules on high-level and domain-specific ontologies are presented and analyzed with respect to the potential use of relation semantics to increase the fidelity of knowledge representation, as well as the potential for reuse and interoperability of knowledge on the Semantic Web.
ON THE ONLINE PARAMETER ESTIMATION PROBLEM IN ADAPTIVE SOFTWARE TESTING
Authors: CAI KAI-YUAN , CHEN TSONG YUEH , LI YONG-CHAO , YU YUEN TAK , ZHAO LEI
Published: July 2008

Software cybernetics is an emerging area that explores the interplay between software and control. The controlled Markov chain (CMC) approach to software testing supports the idea of software cybernetics by treating software testing as a control problem, where the software under test serves as a controlled object modeled by a controlled Markov chain and the software testing strategy serves as the corresponding controller. The software under test and the corresponding software testing strategy form a closed-loop feedback control system. The theory of controlled Markov chains is used to design and optimize the testing strategy in accordance with the testing/reliability goal given explicitly and a priori. Adaptive software testing adjusts and improves software testing strategy online by using the testing data collected in the course of software testing. In doing so, the online parameter estimations play a key role. In this paper, we study the effects of genetic algorithm and the gradient method for doing online parameter estimation in adaptive software testing. We find that genetic algorithm is effective and does not require prior knowledge of the software parameters of concern. Although genetic algorithm is computationally intensive, it leads the adaptive software testing strategy to an optimal software testing strategy that is determined by optimizing a given testing goal, such as minimizing the total cost incurred for removing a given number of defects. On the other hand, the gradient method is computationally favorable, but requires appropriate initial values of the software parameters of concern. It may lead, or fail to lead, the adaptive software testing strategy to an optimal software testing strategy, depending on whether the given initial parameter values are appropriate or not. In general, the genetic algorithm should be used instead of the gradient method in adaptive software testing. Simulation results show that adaptive software testing does work and outperforms random testing.
DESIGNING CUSTOMIZED AND TAILORABLE VISUAL INTERACTIVE SYSTEMS
Authors: COSTABILE MARIA FRANCESCA , FOGLI DANIELA , MARCANTE ANDREA , MUSSIO PIERO , PROVENZA LOREDANA PARASILITI , PICCINNO ANTONIO
Published: July 2008

This paper presents a novel participatory approach to the design of customized and tailorable visual interactive systems; it includes end users as domain experts in the design team. A design method is described which leads to two different visual specifications, one suitable for end users and the other suitable for software engineers. It is also shown how this second specification is directly mapped to the implementation architecture, based on XML technology. The discussion is supported by the description of an example in the mechanical engineering domain.
NUMERICAL ANALYSIS OF LARGE-SCALE SOUND FIELDS USING ITERATIVE METHODS PART II: APPLICATION OF KRYLOV SUBSPACE METHODS TO FINITE ELEMENT ANALYSIS
Authors: OKAMOTO NORIKO , TOMIKU REIJI , OTSURU TORU , YASUDA YOSUKE
Published: July 2008

Krylov subspace iterative solvers are applied to large-scale finite element sound-field analyses of architectural rooms. First, convergence behaviors are compared among four iterative solvers. Results show that the Conjugate Orthogonal Conjugate Gradient (COCG) method offers the best characteristics for finite-element (FE) analysis from the viewpoint of robustness of convergence and computation time. Two investigations to reduce the computation time of the COCG method were carried out. Results show the following. (1) The mean residual of sound pressure levels between COCG method and direct method is less than 0.1 dB if the convergence criterion is set to 10-4 and the maximum residual of those between COCG method and direct method is less than 0.2 dB if the convergence criterion is set to 10-6. (2) The computation time of the COCG method with diagonal preconditioning is about 30% shorter than that of COCG method without preconditioning. Finally, sound pressure level distributions obtained using the authors' FEM are compared to those obtained using fast multipole BEM (FMBEM) and measurements.
RELATIONSHIP BETWEEN THE AXIAL WAVE, AND FIRST NORMAL MODES FOR DUCTED, PROPAGATION IN A WAVEGUIDE
Authors: GRIGORIEVA NATALIE S. , FRIDMAN GREGORY M.
Published: July 2008

For ducted propagation in a waveguide when the source and receiver are placed close to the depth of the waveguide axis, there exist cusped caustics repeatedly along the axis. In neighborhoods of these cusped caustics, the interference of the wave fields that correspond to near-axial rays occurs. This results in the formation of a coherent structure (the axial wave) that propagates along the waveguide axis like a wave. In this paper, for the two-dimensional reference point source problem with the parabolic index of refraction squared the axial wave is represented in the form of a sum of the first normal modes and a remainder field. The mathematical framework is provided by two different representations of the acoustic field. The first one was obtained by Grigorieva et al.1 It includes a sum of ray summands and the axial wave. The second representation including ray summands, a sum of the first normal modes, and a remainder field is derived in the present paper. For the remainder a simple formula including a special function is obtained. Numerical simulations are carried out for parameters corresponding to long-range ocean acoustic propagation experiments.
A FLUX-BASED CONSERVATION APPROACH FOR ACOUSTIC PROBLEMS
Authors: MASSÉ NADIA , PRAX CHRISTIAN , REDON EMMANUEL
Published: July 2008

In this paper a Control Volume Finite Element Method for harmonic acoustic problems is presented. A dispersion analysis for control volume constructed on Q1 finite elements is compared to Galerkin FEM. The spatial convergence is also given in an eigenfrequency determination process for a cavity. The application for exterior acoustic problems is also studied by dividing the whole field into inner and outer domains using a fictitious boundary. A control volume formulation is used to compute the inner field of the truncated problem, and several approaches are combined to describe the outer field behavior on the outside of the fictitious boundary. The task of coupling is easily implemented through the balance of local flux through polygonal volumes. A two-dimensional configuration with a circular interface demonstrates the validity of this approach.
COUPLED MODE AND FINITE ELEMENT APPROXIMATIONS OF UNDERWATER SOUND PROPAGATION PROBLEMS IN GENERAL STRATIFIED ENVIRONMENTS
Authors: ATHANASSOULIS G. A. , BELIBASSAKIS K. A. , MITSOUDIS D. A. , KAMPANIS N. A. , DOUGALIS V. A.
Published: July 2008

We compare the results of a coupled mode method with those of a finite element method and also of COUPLE on two test problems of sound propagation and scattering in cylindrically symmetric, underwater, multilayered acoustic waveguides with range-dependent interface topographies. We observe, in general, very good agreement between the results of the three codes. In some cases in which the frequency of the harmonic point source is such that an eigenvalue of the local vertical problem remains small in magnitude and changes sign several times in the vicinity of the interface nonhomogeneity, the discrepancies between the results of the three codes increase, but remain small in absolute terms.
MESOSCALE SPHERICAL AND PLANAR ORGANIZATIONS OF GOLD NANOPARTICLES
Authors: ZHANG YU XIN , ZENG HUA CHUN
Published: July 2008

We present a systematic investigation on the roles of some starting reagents commonly used in gold nanoparticle synthesis. Our results show that Au nanoparticles adsorbed with tetraoctylammonium bromide (TOAB) or TOAB and 1-dodecanethiol (DDT) can self-assemble into spherical aggregates in various hierarchical forms, such as discrete, linear, and two-dimensional arrays, without using any additional structural linkers. Interestingly, aged Au nanoparticles in different interconnected spherical aggregates are highly ordered, showing long-range lattice uniformity. On the basis of our substrate-dependent experiments, it has been revealed that the sphere formation, self-assembly, and crystallization of Au nanoparticles in the superlattice take place upon drying. A structural evolution of mesoscale spherical assemblies to planar organizations of Au nanoparticles has also been revealed in this work for the first time. In general, the Au nanoparticles are better shelled with TOAB than with DDT surfactant. The symmetrical organic shells of TOAB and its multi-chain structure are believed to be responsible for the high capacity of particle aggregation as well as for the long-range assembling order.
THREE-DIMENSIONAL METALLIC PHOTONIC CRYSTAL BASED ON SELF-ASSEMBLED GOLD NANOSHELLS
Authors: LEE JIN HYOUNG , PARK WOUNJHANG
Published: July 2008

Three-dimensional metallic photonic crystal is fabricated by self-assembly of gold nanoshells. In order to fabricate highly ordered crystal structure, fabrication parameters such as silica coating thickness, the zeta potential and the concentration of gold nanoshells are carefully controlled and optimized. Highly ordered gold nanoshell opal is fabricated and its structural and optical properties are presented.
FLOW CHARACTERISTIC OF AN ELECTRICALLY CONDUCTING MICROPOLAR FLUID OVER A MOVING POROUS PLATE
Authors: KIM YOUN J.
Published: July 2008

An analysis is presented for the problem of unsteady two-dimensional laminar flow of a viscous incompressible electrically conducting micropolar fluid over a semi-infinite vertical moving porous plate in the presence of a transverse magnetic field. Especially, the effect of non-zero values of the micro-gyration vector on the velocity and temperature fields across the boundary layer are investigated, using the method of small perturbation approximation. Numerical results of velocity profiles of micropolar fluids are compared with the corresponding flow problems for a Newtonian fluid. The results show that the effect of increasing values of the micropolar parameter results in decreasing skin friction. It is also observed that the skin friction decreases by increasing the plate moving velocity.
Overbank sediment sampling in Greece: a contribution to the evaluation of methods for the ‘Global Geochemical Baselines’ mapping project
Authors: Demetriades Alecos
Published: July 2008

The different steps in the development of the floodplain or overbank sediment sampling procedure for continental-scale geochemical mapping are described with examples from the Greek pilot project of the Western European Geological Surveys’ Working Group on ‘Regional Geochemical Mapping’. The Greek overbank and stream sediment results were compared statistically with those of the national regional stream sediment survey. The purpose was (1) to compare the geochemistry of overbank sediment, collected from a single site, with that of several tens or hundreds of regional stream sediment samples taken from the upstream drainage basin, and (2) to develop a cost-effective procedure to assess the geochemistry of a drainage basin.
‘
Composite’ samples taken over the whole thickness of the overbank sediment sequence showed that element contents were close to the median, or within the interquartile range, of the same elements in the regional stream sediment samples. Overbank sediment samples collected from pre-defined intervals were not considered satisfactory, for they were taken across overbank sediment layers. Therefore, the method was subsequently refined by collecting samples from different overbank sediment layers, with the recommendation to collect samples at 25-cm intervals when thick layers of over 1 m were encountered.

In selected river basins, surficial overbank and active stream sediments reflect contamination, whereas overbank sediment layers at depth show natural element contents, or pristine conditions. Such data are required for a realistic assessment of the degree of contamination of individual drainage basins. After considering results from Greece and other countries, it is recommended to sample both the surface overbank sediment (0–10 cm), and the deepest possible layer in order to measure pristine or pre-industrial conditions. The Greek results demonstrate that overbank sediments are useful for mapping natural geochemical conditions and baseline concentrations, as well as assessing anthropogenic contamination. The cost-effectiveness of overbank sediment sampling for the ‘Global Geochemical Baselines’ project of the International Union of Geological Sciences (IUGS) and International Association of GeoChemistry (IAGC) is verified.
Low-density geochemical mapping and the robustness of geochemical patterns
Authors: Smith David B. , Reimann Clemens
Published: July 2008

Geochemical mapping of entire continents and, ultimately, the world is still a challenge for applied geochemists. At sample densities traditionally used for geochemical exploration (1 site per 1–25 km
2
), geochemical mapping of whole continents is logistically extremely demanding and tremendously expensive. The first low-density geochemical surveys (1 site per 200 km
2
) were carried out during the late 1960s in Africa. Later surveys conducted in various parts of the world had sample densities ranging from 1 site per 300 km
2
to 1 site per 18 000 km
2
. Although these surveys were deemed successful by the investigators in defining variations in background element content on a regional scale, the scientific community was sceptical that low-density geochemical mapping was possible and would provide useful information. The main area of criticism centred around the concern that at such low sample densities the resulting maps would not be robust, i.e. if the same area were resampled and remapped, different geochemical patterns would emerge. Different examples from the USA, Europe, China and Africa demonstrate that low-density geochemical mapping will result in stable and robust geochemical patterns at the continental scale. Such maps are urgently needed for a wide variety of applications.
Geochemical mapping of the deeply weathered western Yilgarn Craton of Western Australia, using laterite geochemistry
Authors: Cornelius M. , Robertson I.D.M. , Cornelius A.J. , Morris P.A.
Published: July 2008

Multi-element analysis of ferruginous nodules and pisoliths from lateritic residuum, derived lag and ferruginous gravel, selected from locally derived colluvium (laterite) sampled at an approximate 9 km interval (triangular grid) over the western Yilgarn Craton, shows regional geochemical trends, major lithologies and dispersion halos around significant bedrock mineralization. The sample density (one sample per 60–100 km
2
, depending on sample availability) and extent of the coverage (
c
. 400 000 km
2
, including large unsampled areas in drainage) mean that the data are potentially valuable for both exploration and environmental purposes. More than 3100 samples have been analysed for 53 elements by XRF, ICP-AES and ICP-MS, with selected samples also analysed for PGE. Elevated Au abundances in the NE of the survey area not only cluster around known gold deposits but extend beyond them, indicating the likelihood of more widespread mineralization in these areas. A chalcophile element index illustrates potential for Au and base metal mineralization in the westernmost part of the Yilgarn Craton, whereas a pegmatophile index shows a regional NW trend parallel to regional structures. Abundant chromium in granite-dominated areas might indicate mafic-ultramafic remnants (some with anomalous Au) beyond known greenstone belts. A newly discovered regional Hg anomaly trends NW for more than 500 km. Anomalous As, Bi, Mo and Sb along the southern margin of the craton may be related to Au mineralization. The spatial and geochemical consistency of the dataset means that it is well suited to multivariate statistics.
Application of a risk assessment method to Europe-wide geochemical baseline data
Authors: Rapant S. , Salminen R. , Tarvainen T. , Krčmová K. , Cvečková V.
Published: July 2008

The environmental risk, defined as the possibility of impairment of biotic or abiotic components of the environment, derived from geological sources was estimated for the whole of Europe. The assessment was based on data obtained from the Geochemical Atlas of Europe and included measured total concentrations of: Al, As, B, Cd, Cr, Cu, Ni, Pb, Se, Zn, Fe, Mn, Cl, NO
3
and SO
4
in stream water; As, Ba, Cd, Co, Cr, Cu, Hg, Mo, Ni, Pb, V and Zn in topsoil; and As, Cd, Cr, Cu, Hg, Ni, Pb and Zn in stream and floodplain sediments. The number of sampling sites varied from 741 (stream water) to 847 (subsoil). The assessment method was based on the calculation of two-step environmental risk index values (I
ER
) for individually analysed water, soil and sediment samples. Environmental risk quotients are first calculated for each analysed chemical element or compound that exceeds the limit for risk values, and their sum is then calculated. The risk at each site was defined and classified as negligible, low, medium, high, very high or extremely high. The results are presented as risk maps covering the 26 countries of Europe. Stream waters show a high to extremely high risk value in large areas of southern Finland and Sweden, and sporadically in Spain, southern Italy, the Netherlands, northern Germany and Denmark. Stream sediments show high risk values in Greece, Albania, Sardinia and northern Italy. The risk areas for floodplain sediment differ from those for stream sediment, with no high risk values in Sardinia, but instead in Belgium. The highest risk levels in topsoils were detected in Greece, Albania and northern Italy. The combination of all materials shows a medium-level risk throughout Europe and a high to extremely high risk in Greece, Albania, Sicily and Sardinia, and sporadically in Spain, Belgium and the Netherlands. The calculated maps delineate regions where high elevated concentrations pose a risk to the environment, or where the action limits for soil, sediment or water contamination should be revised using the high local baseline.
Environmental geochemical mapping of the Olkusz 1:25 000 scale map sheet, Silesia–Cracow region, southern Poland
Authors: Pasieczna Anna , Lis Józef
Published: July 2008

Detailed, multi-media geochemical mapping has been conducted in the heavily industrialized Silesia–Cracow region in southern Poland. This paper focuses on results for a portion of the region within the Olkusz 1:25 000 scale map sheet as an example. Mapping in the Olkusz area has focused on: topsoils collected from 0–0.3 m; subsoils taken from 0.8–1 m; sediments from streams, ponds, and canals; and surface water. The soils were collected at a sampling density of 16 sites per km
2
. Concentrations of Ag, Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Ni, P, Pb, S, Sr, Ti, V and Zn were determined in topsoil, subsoil and sediments following a hot aqua regia digestion. In addition, organic carbon and grain size distribution were determined in topsoil samples; pH was measured in topsoils, subsoils and surface waters; and conductivity was determined in surface water. Constituents of surface water analysed included Ag, Al, As, B, Ba, Ca, Cd, Cl, Co, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, Rb, Sb, SiO
2
, SO
4
, Sr, Ti, Tl, U and Zn. The results revealed that the soils in the Olkusz map sheet are extremely contaminated with As, Cd, Hg, Pb and Zn in the vicinity of Zn-Pb mines and processing facilities, and that these elements show highly anomalous values in areas where soils were developed on outcrops of Zn-Pb ore-bearing Middle Triassic dolomites. The concentrations of the studied elements decrease exponentially with distance from the sources. The sediments of the main watercourses are polluted with Ag, As, Cd, Pb and Zn. In surface waters of high conductivity and nearly neutral pH, high concentrations of heavy metals and Na, K, Li and SO
4
were observed.
A retargetable parallel-programming framework for MPSoC
Authors: Kwon Seongnam , Kim Yongjoo , Jeun Woo-Chul , Ha Soonhoi , Paek Yunheung
Published: July 2008

As more processing elements are integrated in a single chip, embedded software design becomes more challenging: It becomes a parallel programming for nontrivial heterogeneous multiprocessors with diverse communication architectures, and design constraints such as hardware cost, power, and timeliness. In the current practice of parallel programming with MPI or OpenMP, the programmer should manually optimize the parallel code for each target architecture and for the design constraints. Thus, the design-space exploration of MPSoC (multiprocessor systems-on-chip) costs become prohibitively large as software development overhead increases drastically. To solve this problem, we develop a parallel-programming framework based on a novel programming model called common intermediate code (CIC). In a CIC, functional parallelism and data parallelism of application tasks are specified independently of the target architecture and design constraints. Then, the CIC translator translates the CIC into the final parallel code, considering the target architecture and design constraints to make the CIC retargetable. Experiments with preliminary examples, including the H.263 decoder, show that the proposed parallel-programming framework increases the design productivity of MPSoC software significantly.
Designing secure systems on reconfigurable hardware
Authors: Huffmire Ted , Brotherton Brett , Callegari Nick , Valamehr Jonathan , White Jeff , Kastner Ryan , Sherwood Tim
Published: July 2008

The extremely high cost of custom ASIC fabrication makes FPGAs an attractive alternative for deployment of custom hardware. Embedded systems based on reconfigurable hardware integrate many functions onto a single device. Since embedded designers often have no choice but to use soft IP cores obtained from third parties, the cores operate at different trust levels, resulting in mixed-trust designs. The goal of this project is to evaluate recently proposed security primitives for reconfigurable hardware by building a real embedded system with several cores on a single FPGA and implementing these primitives on the system. Overcoming the practical problems of integrating multiple cores together with security mechanisms will help us to develop realistic security-policy specifications that drive enforcement mechanisms on embedded systems.
Reuse and optimization of testbenches and properties in a TLM-to-RTL design flow
Authors: Bombieri Nicola , Fummi Franco , Pravadelli Graziano
Published: July 2008

In transaction-level modeling (TLM), verification methodologies based on transactions allow testbenches, properties, and IP cores in mixed TL-RTL designs to be reused. However, no papers in the literature analyze the effectiveness of transaction-based verification (TBV) in comparison to the more traditional RTL approach. The first contribution of this article is the introduction of a functional-fault-model-based methodology for demonstrating the effectiveness of reuse through TBV. A second contribution is the introduction of a similar methodology for efficient property checking which identifies and removes redundant properties prior to assertion-based verification or model checking.
Processor virtualization for secure mobile terminals
Authors: Inoue Hiroaki , Sakai Junji , Edahiro Masato
Published: July 2008

We propose a processor virtualization architecture, VIRTUS, to provide a dedicated domain for preinstalled applications and virtualized domains for downloaded native applications. With it, security-oriented next-generation mobile terminals can provide any number of domains for native applications. VIRTUS features three new technologies, namely, VMM asymmetrization, dynamic interdomain communication (IDC), and virtualization-assist logic, and it is first in the world to virtualize an ARM-based multiprocessor. Evaluations have shown that VMM asymmetrization results in significantly less performance degradation and LOC increase than do other VMMs. Further, dynamic IDC overhead is low enough, and virtualization-assist logic can be implemented in a sufficiently small area.
Combining system scenarios and configurable memories to tolerate unpredictability
Authors: Sanz Concepción , Prieto Manuel , Gómez José Ignacio , Papanikolaou Antonis , Miranda Miguel , Catthoor Francky
Published: July 2008

Process variability and the dynamism of new applications increase the uncertainty of embedded systems and force designers to use pessimistic assumptions, which have a tremendous impact on both the performance and energy consumption of their memory organizations. In this article we introduce an experimental framework which tries to mitigate the effects of both sources of unpredictability. At compile time, an extensive profiling helps us to detect system scenarios and bounds application dynamism. At the organization level, we incorporate a heterogeneous memory architecture composed by several configurable memories. A calibration process and a runtime control system adapt the platform to the current application needs. Our approach manages to reduce significantly the energy overhead associated to both variability and application dynamism (up to 60%, according to our simulations) without compromising the timing constraints existing in our target domain of dynamic periodic multimedia applications.
Evolution of synthetic RTL benchmark circuits with predefined testability
Authors: Pecenka Tomas , Sekanina Lukas , Kotasek Zdenek
Published: July 2008

This article presents a new real-world application of evolutionary computing in the area of digital-circuits testing. A method is described which enables to evolve large synthetic RTL benchmark circuits with a predefined structure and testability. Using the proposed method, a new collection of synthetic benchmark circuits was developed. These benchmark circuits will be useful in a validation process of novel algorithms and tools in the area of digital-circuits testing. Evolved benchmark circuits currently represent the most complex benchmark circuits with a known level of testability. Furthermore, these circuits are the largest that have ever been designed by means of evolutionary algorithms. This work also investigates suitable parameters of the evolutionary algorithm for this problem and explores the limits in the complexity of evolved circuits.
On the Failure of Rank-Revealing QR Factorization Software -- A Case Study
Authors: Drmač Zlatko , Bujanović Zvonimir
Published: July 2008

This article reports an unexpected and rather erratic behavior of the LAPACK software implementation of the QR factorization with Businger-Golub column pivoting. It is shown that, due to finite precision arithmetic, the software implementation of the factorization can catastrophically fail to produce a properly structured triangular factor, thus leading to a potentially severe underestimate of a matrix's numerical rank. The 30-year old problem, dating back to LINPACK, has (undetectedly) badly affected many computational routines and software packages, as well as the study of rank-revealing QR factorizations. We combine computer experiments and numerical analysis to isolate, analyze, and fix the problem. Our modification of the current LAPACK xGEQP3 routine is already included in the LAPACK 3.1.0 release. The modified routine is numerically more robust and with a negligible overhead. We also provide a new, equally efficient, and provably numerically safe partial-column norm-updating strategy.
Algorithm 881
Authors: Frayssé Valérie , Giraud Luc , Gratton Serge
Published: July 2008

In this article we describe our implementations of the FGMRES algorithm for both real and complex, single and double precision arithmetics suitable for serial, shared-memory, and distributed-memory computers. For the sake of portability, simplicity, flexibility, and efficiency, the FGMRES solvers have been implemented in Fortran 77 using the reverse communication mechanism for the matrix-vector product, the preconditioning, and the dot-product computations. For distributed-memory computation, several orthogonalization procedures have been implemented to reduce the cost of the dot-product calculation, which is a well-known bottleneck of efficiency for Krylov methods. Furthermore, either implicit or explicit calculation of the residual at restart is possible depending on the actual cost of the matrix-vector product. Finally, the implemented stopping criterion is based on a normwise backward error.
Algorithm 882
Authors: van Deun Joris , Deckers Karl , Bultheel Adhemar , Weideman J. A. C.
Published: July 2008

We present a numerical procedure to compute the nodes and weights in rational Gauss-Chebyshev quadrature formulas. Under certain conditions on the poles, these nodes are near best for rational interpolation with prescribed poles (in the same sense that Chebyshev points are near best for polynomial interpolation). As an illustration, we use these interpolation points to solve a differential equation with an interior boundary layer using a rational spectral method.

The algorithm to compute the interpolation points (and, if required, the quadrature weights) is implemented as a Matlab program.
Algorithm 883
Authors: Waki Hayato , Kim Sunyoung , Kojima Masakazu , Muramatsu Masakazu , Sugimoto Hiroshi
Published: July 2008

SparsePOP is a Matlab implementation of the sparse semidefinite programming (SDP) relaxation method for approximating a global optimal solution of a polynomial optimization problem (POP) proposed by Waki et al. [2006]. The sparse SDP relaxation exploits a sparse structure of polynomials in POPs when applying “a hierarchy of LMI relaxations of increasing dimensions” Lasserre [2006]. The efficiency of SparsePOP to approximate optimal solutions of POPs is thus increased, and larger-scale POPs can be handled.
Algorithm 884
Authors: Domínguez Víctor , Sayas Francisco-Javier
Published: July 2008

In this work we propose a new algorithm to evaluate the basis functions of the Argyris finite element and their derivatives. The main novelty here is an efficient way to calculate the matrix which gives the change of coordinates between the bases of the Argyis element for the reference and for an arbitrary triangle. This matrix is factored as the product of two rectangular matrices with a strong block structure which makes their computation very easy. We show and comment on an implementation of this algorithm in Matlab. Two numerical experiments, an interpolation of a smooth function on a triangle and the finite-element solution of the Dirichlet problem for the biLaplacian, are presented in the last section to check the performance of our implementation.
Designing the perfect auction
Authors: Varian Hal R.
Published: July 2008

Distributed algorithmic mechanism design is a field at the intersection of computer science and economics.
From the front linesSoftware development amidst the whiz of silver bullets
Authors: Bell Alex E.
Published: July 2008

Software development organizations must accept the inevitability of silver-bullet solution proposals and devise strategies to defend against them.
The q-WZ method for infinite sums (abstract only)
Authors: Chen William Y.C. , Xia Ernest X.W.
Published: July 2008

We develop a q-WZ method for justifying nonterminating basic hypergeometric summation formulas by computing the WZ-pairs as certificates which may involve some infinite q-shifted factorials. Using this approach, we can verify a wide variety of classical summation formulas, with typical examples including the q-binomial theorem, the q-Gauss sum, the 6ψ5 sum, the Ramanujan 1ψ1 sum, and Bailey's 6ψ6 sum. In many cases we can discover the companion identities. This work is inspired by the study of two elegant identities involving partial theta functions due to Andrews and Warnaar from the telescoping viewpoint. The key point lies in the fact that the q-Gosper algorithm is effective to deal with q-hypergeometric terms multiplied by the infinite q-shifted factorials.
Algebraic computations and applications to geometry (abstract only)
Authors: Tsigaridas Elias P.
Published: July 2008

Real algebraic numbers are the real numbers that are real roots of univariate polynomials with integer coefficients. We study exact algorithms, from a theoretical and an implementation point of view, based on integer arithmetic of arbitrary precision, for computations with real algebraic numbers and applications of these algorithms on problems and algorithms in non linear computational geometry.

In order to construct a real algebraic number we must compute the real roots of a univariate polynomial with integer cofficients. We unify and simplify the theory behind the subdivision based algorithms for real root isolation and we improve the complexity of the algorithm that is based on the continued fraction expansion of the real numbers. The best known complexity bound up today is achieved using new techniques. Moreover, we prove that the bound holds for non square-free polynomials and that in the same complexity bound we can compute the multiplicities of the real roots. We prove a new bound for the expected complexity of the algorithm based on continued fractions. We generalize the real root isolation algorithms to bivariate polynomial systems. Our experimental analysis proves the effectiveness of our methods.

The algorithms that we consider for computations with real algebraic numbers are construction, comparison, sign evaluation and quantifier elimination. If the degree of the polynomial is small, i.e. ≤ 4 in the univariate case and ≤ 2 in the bivariate case, we propose special purpose algorithms that have constant arithmetic complexity. For all the algorithms we present a C++ implementation and an experimental analysis.

In computational geometry we study the predicates needed by the algorithms for the arrangement of elliptic arcs in the plane and the computation of the Voronoi diagram of ellipses, also in the plane. Finally, given a convex lattice polygon we study algorithms for decomposing it to two other convex lattice polygons, such that their Minkowski sum is the original polygon.
Applications of the gröbner fan to gene network reconstruction (abstract only)
Authors: Dimitrova Elena S. , Stigler Brandilyn , Jarrah Abdul Salam , Laubenbacher Reinhard
Published: July 2008

Gröbner fans have gained popularity in computational commutative algebra and algebraic geometry with applications ranging from Gröbner basis conversion to the emerging field of tropical mathematics. Recently Gröbner fans have been employed for the selection of minimal models that fit measurement data from gene regulatory networks. The model space is described as the sum of an interpolating polynomial function f and the set of all polynomials that vanish on the data, that is, the ideal of data points. A minimal model can be chosen by computing the reduction of f with respect to a fixed Gröbner basis, which is dependent on the choice of term order. As Gröbner fans partition the set of Gröbner bases into equivalence classes, they can be thought of as parametrizations of the model space. This characterization permits exploration of the model space and discovery of "most likely" models. In this poster we show how Gröbner fans are used to two reconstruct gene regulatory networks: lactose metabolism in the bacterium E. coli and tissue development in the roundworm C. elegans.
An attack on improved algebraic surface public-key cryptosystem (abstract only)
Authors: Iwami Maki
Published: July 2008

Public key cryptography is widely used because it enables secure communication with a party accessing the site for the first time. But it is widely known that the quantum computers become available then the public key cryptosystems based on the discrete logarithm probrem such as RSA cryptosystem and Elliptic Curve cryptosystem will no longer be secure. To address these issues, Akiyama-Goto algebraic Surface Public-key Cryptosystem (ASC) was developed [1], and opened to general public at website as a research news of Toshiba corporation in 2005. Its security is based on a decision randomizing polynomial problem which is related to a problem of finding sections on fibered algebraic surfaces. This problem can be reduced to solving a multivariate equation system and it is known to be NP-complete. In 2007, in the case that public-key is in a certain form, Uchiyama and Tokunaga successed to attack in the sense of getting plain text from cipher text using reductions efficiently without solving section finding problem [2].And the abstract is introduced in CRYPTREC report 2006 [3] in the Appendix Chapter, which is known to be the important report related to e-Government recommended ciphers in Japan. Note that, at this point, the cryptosystem can be used safely if only we avoid to adopt using public key with vulnerability in the key generation step. However, the author suggested two algorithms applicable to all cases [5] i.e. the cryptosystem is completely broken. One is the generalization of Uchiyama-Tokunagas attack from polynomial ring over IFp to polynomial ring over rational function field. And the other takes advantages of Grobner base techniques so as to deal with in the polynomial ring over IFp. And in [6], the author also suggested methods for calculating zero point of the algebraic surface and a new attack utilizing it, and the approach resulted in the difficulty of making a suggestion of the invulnerable algebraic surface public-key cryptosystem without changing ideas progressively. On the other hand, Inanov-Volochs attack using trace map [9] was developed. In these background, Akiyama-Goto developed improved version of their Algebraic surface public-key cryptosystem (improved ASC) [8] on January 2008 [8] which has tolerance to Uchiyama-Gotos attack using reduction and Volochs attack using the trace map. Ivanov and Voloch suggested the substitution attack briefly on improved ASC in section 3 in [9], but the details are unspecified. In section 2, the improved ASC is described, and then, in section 3, a new reduction attack on the improved ASC is presented.
SAGE and coding theory (abstract only)
Authors: Joyner David , Miller Robert
Published: July 2008

This is a very brief survey of recent work in SAGE on implementing algorithms to compute with linear block codes. http://www.sagemath.org.

SAGE is a mathematical software package similar to the "big M's" (Maple, Mathematica, Magma, and Matlab) but free and open source. Download information and manuals are available at http://www.sagemath.org/. Included in SAGE is the group theory package GAP and GUAVA, GAP's coding theory package. All of GUAVA's functions can be accessed within SAGE.
Factoring univariate polynomials over the rationals (abstract only)
Authors: Novocin Andrew
Published: July 2008

This poster presents an algorithm for factoring polynomials over the rationals which follows the approach of the van Hoeij algorithm. The key theoretical novelty in our approach is that it is set up in a way that will make it possible to prove a new complexity result. Another difference of this algorithm from prior algorithms is the practical improvement which we call early termination. Our algorithm should outperform prior algorithms in many common classes of polynomials (including irreducibles).
Connectivity in semialgebraic sets (abstract only)
Authors: Quinn Robert , Hong Hoon
Published: July 2008

A semialgebraic set is a subset of real space defined by polynomial equations and inequalities. A semialgebraic set is a union of finitely many maximally connected components. In this talk, we consider the problem of deciding whether two given points in a semialgebraic set are connected, that is, whether the two points lie in the same connected component. In particular, we consider the semialgebraic set defined by f not equal 0 where f is a given bivariate polynomial. The motivation comes from the observation that many important/non-trivial problems in science and engineering can be often reduced to that of connectivity. Due to its importance, there has been intense research effort on the problem. We will describe a method based on gradient fields and provide a sketch of the proof of correctness based on the Morse complex. The method seems to be more efficient than the previous methods in practice.
A Tribute to Jim Gray
Authors: Allman Eric
Published: July 2008

Computer science attracts many very smart people, but a few stand out above the others, somehow blessed with a kind of creativity that most of us are denied. Names such as Alan Turing, Edsger Dijkstra, and John Backus come to mind. Jim Gray is another.
A New Era
Authors: Maurer James
Published: July 2008

I want to remind you that this will be the last printed issue of Queue but also to reassure you that Queue is not going away. As I mentioned in my letter in the last issue, ACM has decided to migrate Queue to the Web. As of July 2008, Queue will expand its publication frequency to 10 issues per year and publish those issues online using the most cutting-edge digital-editions technology available, as well as revamp the existing Queue Web site to provide an overall improved user experience.
The Virtue of Paranoia
Authors: Neville-Neil George
Published: July 2008

Dear KV, I just joined a company that massages large amounts of data into an internal format for its own applications to work on. Although the data is backed up regularly, I have noticed that access to this data, which has accumulated to be several petabytes in size, is not particularly well secured. There is no encryption, and although the data is not easily reachable from the Internet, everyone at the company has direct access to the volumes, both physically and electronically, all the time. Our data center is not particularly well protected either, with just two locked office doors between the outside world and the machines inside.