bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of Analyses for Moored Systems in Random Waves
Authors: Eatock Taylor R. , Sincock P.
Published: November 2009

This paper investigates methods of simulating the combined wave frequency and low-frequency wave drift forces and motion responses of floating systems. This is motivated by the requirement for estimates of response statistics for systems on nonlinear moorings. Results are given for a linear system for which experimental data are available (an articulated column model); and for a moored barge on mildly and strongly nonlinear moorings. Estimates are obtained for low-frequency spectra, linear and quadratic transfer functions, response probability distributions, and peak distributions.
Anisotropic Sea Ice Indentation in the Creeping Mode
Authors: Sunder S. Shyam , Ganguly J. , Ting S.-K.
Published: November 2009

An orthotopic elastic-power law creep model for sea ice is presented and then a finite element method of analysis is developed and applied to study the effect of sea ice anisotropy on indentation in the creeping mode. Numerical simulations are performed under plane stress conditions to predict the influence of interface adfreeze and friction, variability in parameters of a transversely isotropic material model for sea ice, rubble pile or grounded ice foot, and ice sheet velocity on global forces and local pressures generated on a rigid cylindrical indenter. The results are compared with those from an approximate method of analysis based on the upper bound theorem. Interface pressure distributions are obtained in addition to contours of stress and strain.
A Hybrid Integral Equation Method for Wave Forces on Three-Dimensional Offshore Structures
Authors: Yuen M. M. F. , Chau F. P.
Published: November 2009

Wave forces on arbitrary-shaped three-dimensional offshore structures are analyzed by the proposed hybrid integral equation method. Eigenfunction expansion is used to represent velocity potential in the outer domain, while a set of integral equations is developed for the inner domain encompassing the structure. A floating dock and a step cylinder are used as test cases showing the validity of the method.
Analytical Study of the Mechanical Strength of Flexible Pipes
Authors: Goto Y. , Okamoto T. , Araki M. , Fuku T.
Published: November 2009

Although flexible pipes have already been in wide use in the offshore industry, studies on their mechanical strength are few and far between, and their industrial standards are yet to be established. This paper describes the analytical methods employed in determining the mechanical strength of flexible pipes and also discusses test data that delineate the characteristics of flexible pipes. The axial, torsional and crushing strength of flexible pipes is studied along with their damaging bending on the basis of our results of analysis and testing. The coincidence of the results of theoretical analysis with test results indicates that our analytical methods provide a useful tool for determining the design mechanical strength of flexible pipes.
Far-Field Current Model for Carbon Steel Gas Pipes
Authors: Kikuta T. , Fisher J. L. , Rowland S. N. , Jolly W. D.
Published: November 2009

The far-field eddy current effect refers to an observed phenomenon in electrically conducting tubular material in which the amplitude of an electromagnetic field induced at one location decays relatively slowly with distance along the tube. This effect and its usefulness for nondestructive evaluation of ferromagnetic pipe were noted as early as 1951 [1]. However, no published work of which the authors are aware has attempted more than a qualitative explanation of the far-field effect [2]. This paper presents a semi-empirical model, verified in laboratory experiments, that describes the behavior quantitatively. The experiments and model show that the far-field effect is due to the presence of a directly coupled wave that is rapidly attenuated by the pipe geometry. The directly coupled wave, in turn, excites eddy currents that travel through the pipe wall and then along the outer surface of the pipe with relatively low attenuation. The model allows an understanding of how the effect scales for varying pipe diameters, wall thicknesses, conductivity, and permeability as well as some aspects of probe design.
Effect of Shear Deformation and Rotatory Inertia on Dynamic Buckling
of Elastic Plates
Authors: Birman V.
Published: November 2009

The influence of shear deformation and rotatory inertia on dynamic response of elastic rectangular plates subject to in-plane loads increasing with time is discussed using Mindlin’s plate theory. The qualitative effect of those factors on transverse displacements is estimated. It is shown that this effect becomes essential only if the plate is thick and the number of half-waves along the plate axes in the deformation mode is large.
Mooring Systems: A State-of-the-Art Review
Authors: Skop R. A.
Published: November 2009

A mooring system is any system of cables and anchors used to restrain the motion of a fixed or floating structure by transmitting the forces on the structure to the seafloor. Examples of mooring systems range from the simple single-anchor, single-line system used to restrain meteorological buoys to the complex systems used to restrain tension leg platforms and guyed towers for deepwater oil operations. In this paper, a state-of-the-art review regarding the behavior of cables as mooring system components, the types and selection of cables, and the various classes of anchors and their applications is presented.
Prediction of the Current Structure Under Drifting Pack
Ice
Authors: Myrhaug D.
Published: November 2009

A simple analytical theory which describes the motion in a turbulent planetary boundary layer near a rough sea bed by using a two-layer eddy viscosity model is presented. An inverted boundary layer similar to that at the sea bed is applicable under the pack ice. The vertical structure of the current in the boundary layer is presented, and comparisons are made with data from McPhee and Smith [1] obtained from measurements of the turbulent boundary layer under drifting Arctic pack ice. The present model predictions for the drag coefficient at the ice surface and the direction of the surface shear stress are also compared with corresponding formulas given in Davenport [2], which are obtained as fits to observations in atmospheric boundary layers.
Assessment of Two Neglected Effects in the Analysis of an Oil Pumping Ring Seal
Authors: Smith P. J. , Keith T. G.
Published: November 2009

Many factors have been found to affect the performance of a pumping ring seal. In this paper, two effects (elevated reservoir temperature and rod deformation), both heretofore neglected, are assessed through the use of a thermoelastohydrodynamic numerical model of the pumping ring. Elevated reservoir temperatures are found to result in an increase in the amount of lubricant pumped while deformation of the translating rod is shown to cause a reduction in the lubricant pumped.
Elastoplastic Contact of Bodies With Friction Under Normal and Tangential Loading
Authors: Nagaraj H. S.
Published: November 2009

During the relative motion of surfaces, which are in partial contact, asperities on them interact with one another. A pair of contacting asperities has been modeled as a rigid body contacting an elasto plastic half-space under combined normal and tangential loading. A displacement formulation of the finite element method was used to solve for stresses and displacements. An elastic-plastic type of material behavior with linear strain-hardening was assumed. Results have been obtained for normal approach only, and for normal approach with tangential displacement. At sufficiently high loads, a significant portion of the material under the contact area is in the plastic regime. However, the elastic region lying beneath the plastified area appears to have a major influence on the peak contact pressure and the tangential compliance of contacting bodies. Small relative tangential displacements were found to have only a slight influence on the pressure distribution, but their influence on the extent of the plastified area was found to be significant. These findings may be important for the analytical modeling of surface interactions.
Dynamic Characteristics of Finite Porous Journal Bearings Considering Tangential Velocity Slip
Authors: Chattopadhyay A. K. , Majumdar B. C.
Published: November 2009

A theoretical investigation to find out the dynamic characteristics of porous journal bearings of finite length has been carried out considering the Beavers-Joseph crierion of velocity slip at the bearing film interface. It has been shown that the effect of velocity slip on the dynamic characteristics is small.
Development of Titanium Needle Probes for Neural Recording and Evaluation of Magnetic Resonance Imaging Artifacts
Authors: Yoon Hargsoon , Deshpande Devesh C. , Kim T. H. , Jeong Eun-Kee , Harbaugh Robert E. , Varadan Vijay K.
Published: November 2009

The aim of this research is to develop a mechanically flexible and strong neural probe with microelectrode array for future clinical applications in neural prosthetics and neurological disorder fields. This research specifically focuses on the development of neural recording electrodes with iridium oxide (IrOx) electrodes on a titanium needle probe and discusses the fabrication techniques and their evaluation for physical properties and electrochemical performance. Microfabrication processes, such as inductive coupled plasma etching, were used to deeply etch the Ti needle structures on titanium foils, and microelectrode arrays with iridium oxide films were formed by electrochemical deposition for low impedance neural recording. Mechanical and electrochemical analyses were performed to verify the viability of Ti needle probes in vitro. The final section of this paper addresses the issue of magnetic resonance imaging artifacts of titanium needle probes, and test results are compared with similarly fabricated Si needle probes. The advantages of using a titanium needle probe are discussed in the application of neural probe electrodes, as well.
Smells Like a Hormone?
Authors: Adler Elizabeth M.
Published: November 2009

Some odorants can activate nuclear estrogen receptors, as well as cell surface odor receptors.
Physical mapping of a 7A.7D translocation in the wheat–Thinopyrum ponticumpartial amphiploid BE-1 using multicolour genomic in situ hybridization and microsatellite marker analysis
Authors: Sepsi A. , Molnár I. , Molnár-Láng M.
Published: November 2009

The absence of chromosome 7D in the wheat–Thinopyrum ponticum partial amphiploid BE-1 was detected previously by multicolour genomic in situ hybridization, sequential FISH (fluorescence in situ hybridization) using repetitive DNA probes, and SSR marker analysis. In the present study the previous cytogenetic and SSR marker analyses were expanded to include 25 other SSR markers assigned to wheat chromosomes 7A and 7D to confirm the presence of a 7A.7D translocation and to specify its composition. An almost complete chromosome 7A and a short chromosome segment derived from the terminal region of 7DL were detected, confirming the presence of a terminal translocation involving the distal regions of 7AL and 7DL. In both cases the position of the translocation breakpoint was different from that of known deletion lines. The identification of the 7AL.7DL translocation and its breakpoint position provides a new physical landmark for future physical mapping studies, opening up the possibility of more precise localization of genes or molecular markers within the terminal regions of 7DL and 7AL.
Microsatellite-based evaluation of Ribes spp. germplasm
Authors: Cavanna M. , Torello Marinoni D. , Beccaro G. L. , Bounous G.
Published: November 2009

There is a lack of published microsatellite data which characterizes Ribes spp. To address this, an initial study of simple sequence repeat (SSR) variation was undertaken in 41 cultivars belonging to four species of the genus Ribes to evaluate its genetic variability. The cultivars were collected in Piedmont, northwest Italy, together with one cultivar from Switzerland. Twenty SSRs were screened for amplification and polymorphism. Seven failed to amplify, and therefore the remaining 13 were selected and used to fingerprint all the cultivars. Microsatellite analysis resulted in the identification of 38 genotypes, suggesting the existence of possible clonal genotypes and synonyms. Among the cultivars analyzed, two tetraploid accessions were found. The evaluation of genetic variability in Ribes is of fundamental importance for future nutritional breeding programs and to preserve genetic resources, as cultivar characterization permits better management of plant collections.
Risk assessment of buildings against blast effectsThis article is one of a selection of papers published in the Special Issue on Blast Engineering.
Authors: Foo Simon , von Rosen Bert , Contestabile Ettore
Published: November 2009

Because of changes in functional or security requirements, many new or existing buildings are now required to resist blast loads. New buildings can be designed and constructed to resist defined blast loads. Existing buildings, on the other hand, would have to rely on a risk assessment to determine both its vulnerability to blast effects and the necessary measures to mitigate the unacceptable blast effects. A rapid screening methodology has been developed for conducting a preliminary assessment of buildings against external blast effects. The methodology accounts for the threat, the vulnerability of the building, the consequence of an event and the risk, which is the product of the threat and the consequence. The rapid screening methodology has been applied to several buildings and the results are reasonable. This paper presents the rapid screening methodology and its application to two federal buildings in Canada.
Anticipating the post-blast condition of structuresThis article is one of a selection of papers published in the Special Issue on Blast Engineering.
Authors: Dusenberry Donald O.
Published: November 2009

Designers charged to develop blast-resistant structural designs must be able to address the technical aspects of the explosion process and provide structural components with sufficient strength and ductility to resist the applied pressures. The blast environment is different from those of other loads with which designers deal, and uncertainties about the actual response of structures often are higher. For these reasons, designers often have less confidence in their abilities to explain to their clients their expectations about the actual response of the building to a blast event. This paper identifies some elements of the conventional design process that do not translate directly to blast-resistant design, reasons why uncertainties in performance expectations differ from those encountered with other load sources, and the need to understand and acknowledge residual risks for the facade, the structure, and the safety of the occupants of blast resistant buildings.
Establishing a risk-assessment process for release of genetically modified wine yeast into the environment
Authors: Schoeman Heidi , Wolfaardt Gideon M. , Botha Alfred , van Rensburg Pierre , Pretorius Isak S.
Published: November 2009

The use and release of genetically modified organisms (GMOs) is an issue of intense public concern and, in the case of food and beverages, products containing GMOs or products thereof carry the risk of consumer rejection. The recent commercialization of 2 GM wine yeasts in the United States and Canada has made research and development of risk assessments for GM microorganisms a priority. The purpose of this study was to take a first step in establishing a risk-assessment process for future use and potential release of GM wine yeasts into the environment. The behaviour and spread of a GM wine yeast was monitored in saturated sand columns, saturated sand flow cells, and conventional flow cells. A widely used commercial Saccharomyces cerevisiae wine yeast, VIN13, a VIN13 transgenic strain (LKA1, which carries the LKA1 α-amylase gene of Lipomyces kononenkoae ), a soil bacterium ( Dyadobacter fermentens ), and a nonwine soil-borne yeast ( Cryptococcus laurentii ) were compared in laboratory-scale microcosm systems designed to monitor microbial mobility behaviour, survival, and attachment to surfaces. It was found that LKA1 cells survived in saturated sand columns, but showed little mobility in the porous matrix, suggesting that the cells attached with high efficiency to sand. There was no significant difference between the mobility patterns of LKA1 and VIN13. All 3 yeasts (VIN13, LKA1, and C. laurentii) were shown to form stable biofilms; the 2 S. cerevisiae strains either had no difference in biofilm density or the LKA1 biofilm was less dense than that of VIN13. When co-inoculated with C. laurentii, LKA1 had no negative influence on the breakthrough of the Cryptococcus yeast in a sand column or on its ability to form biofilms. In addition, LKA1 did not successfully integrate into a stable mixed-biofilm community, nor did it disrupt the biofilm community. Overall, it was concluded that the LKA1 transgenic yeast had the same reproductive success as VIN13 in these 3 microcosms and had no selective advantage over the untransformed parental strain.
Recovery of antimicrobial-resistantEscherichia coliafter storage of bovine feces in Cary–Blair medium
Authors: Alexander T. W. , Booker C. W. , Gow S. P. , Read R. R. , McAllister T. A.
Published: November 2009

The effect of storing bovine feces in Cary–Blair medium on the recovery of antimicrobial-resistant Escherichia coli was investigated. Feces from cattle at a research feedlot (n = 50) and at a commercial feedlot (n = 46) were processed immediately or after storage in Cary–Blair medium for 8 days at 5 °C. Total, ampicillin-resistant, and tetracycline-resistant E. coli were isolated. The number of total E. coli decreased slightly after storage (0.19 log units; p < 0.001), but storage of feces in Cary–Blair medium did not affect recovery of ampicillin- or tetracycline-resistant E. coli.
The role of rpoS on the survival of a p-nitrophenol degrading Pseudomonas putida strain in planktonic and biofilm phases
Authors: Maki M. L. , Lawrence J. R. , Swerhone G. D.W. , Leung K. T.
Published: November 2009

The survival of and interactions between a Pseudomonas putida strain labelled with a red fluorescent protein gene (WT-rfp) and its green fluorescent protein gene-labelled rpoS– mutant (KO-gfp) were examined. The generation times of the planktonic WT-rfp and KO-gfp in trypticase soy broth were not significantly different (i.e., p > 0.05) from each other at 30 °C. However, the biovolume of the KO-gfp biofilm was about 7 times larger than its WT-rfp counterpart after 48 h of growth. Furthermore, the presence of WT-rfp suppressed the biofilm development of KO-gfp significantly in co-culture biofilms. In planktonic conditions, the pre-carbon-starved WT-rfp achieved a 3-fold greater survival than the pre-carbon-starved KO-gfp in 0.85% saline after a 13-day incubation. In a 1:1 ratio co-culture, the pre-carbon-starved WT-rfp outcompeted the pre-carbon-starved KO-gfp by 20-fold. However, the survival of WT-rfp and KO-gfp were not significantly different from each other in biofilm conditions. Additionally, 11.4% and 61.2% of the WT-rfp and KO-gfp biofilms, respectively, remained intact after washing in 0.2% SDS for 60 min. In conclusion, the rpoS had a significant impact on survival and competitiveness of planktonic P. putida, and on biofilm development, being implicated in competitive suppression of biofilm development in co-culture biofilms and decreased biofilm cohesiveness.
Failure to estimate reliable sex ratios of guanaco from road-survey data
Authors: Pedrana Julieta , Rodríguez Alejandro , Bustamante Javier , Travaini Alejandro , Zanón Martínez Juan I.
Published: November 2009

The guanaco ( Lama guanicoe (Müller, 1776)) is a monomorphic polygynous mammal whose adult sex ratio is expected to be balanced or biased towards females. Remarkably male-biased sex ratios of adult guanacos are often estimated from road surveys. We analyzed the distribution of guanaco social groups recorded during road surveys in Patagonia, Argentina, to test the hypothesis that group assignation based upon behavioral traits is not unequivocal and can be biased by survey factors. Guanacos are organized into three social units (family groups, male groups, and solitary males) that are identified by their grouping behaviour. We recorded 992 guanaco groups, and estimated an adult sex ratio of 3.2 males/female. We used generalized additive models to test the null hypothesis that the probability of recording a group as a family group was constant. Alternatively, this probability could decrease when juvenile abundance and (or) detectability was low. The most parsimonious model showed that the probability of classifying a “family” group increased with date, and decreased with group size, distance to the observer, and time of day. Our results do not support the null hypothesis and suggest that road surveys are unsuitable to estimate reliably the social structure or sex ratio of guanaco populations.
Effects of predaceous and nonpredaceous introduced fish on the survival, growth, and antipredation behaviours of long-toed salamanders
Authors: Pearson K. J. , Goater C. P.
Published: November 2009

Simultaneous introduction of complex suites of exotic organisms into indigenous populations have poorly known magnitudes and consequences. We compared the effects of introduced piscivorous rainbow trout ( Oncorhynchus mykiss (Walbaum, 1792)) and nonpiscivorous fathead minnows ( Pimephales promelas Rafinesque, 1820) on growth, survival, susceptibility to predation, and antipredator behaviours of naïve long-toed salamanders ( Ambystoma macrodactylum Baird, 1850). Trout reduced salamander hatchling and larvae survival to nearly zero in predation trials and caused a 39% reduction in salamander survival within outdoor mesocosms. Salamander larvae did not increase their refuge use or alter activity patterns in the presence of trout. These results imply that allotopic distributions of trout and salamanders observed in several field surveys likely result from the inability of larvae to recognize introduced predators as a threat. Minnows also caused significant reductions in salamander survival (41%) and growth (37%) in mesocosms, and exposure to minnow cues caused larvae to spend more time within a refuge. Reduced salamander survivorship and growth in the mesocosms was likely due to competition for limiting zooplankton and (or) cannibalism. These results indicate that introductions of small-bodied, nonpiscivorous fishes can reduce amphibian survival and growth to at least the same extent as introduced trout.
Z-SCAN MEASUREMENTS OF OPTICAL NONLINEARITIES OF DYE-DOPED LIQUID CRYSTALS
Authors: LIN HUI-CHI , FUH ANDY YING-GUEY
Published: November 2009

Nematic liquid crystal (NLC) is a material that features a large nonlinear optical response. The nonlinearity can be enhanced by doping a dye agent into a NLC host. In this paper, we review the nonlinear phenomena recently observed for dye-doped liquid crystal (DDLC) films measured using the Z-scan technique, which is a simple, yet powerful method for measuring nonlinear refractive indices (optical Kerr constant) n2 and nonlinear absorption coefficients β. The nonlinear effects of liquid crystals (LCs) include the electronic polarization effect, electrostriction effect, thermal effect and reorientation effect. When LCs are doped with dye agents, the dye-induced orientational effect, photoisomerization effect, and light-induced thermal effect come about to enhance LC nonlinearity. The dominant effect depends strongly upon the spatial, temporal and polarization properties of the excitation laser beam. Generally speaking, the nonlinear effects resulted from the electronic polarization and photoisomerization effects arise from a laser pulse on picosecond duration scale, while electrostriction, thermal and reorientation effects occur on nanosecond ~ microsecond, nanosecond ~ millisecond and millisecond ~ second duration scales, respectively. In this paper, the causation of nonlinear refractive index n2 into various different experimental conditions is summarized, including the changes of the external electric field, external optical field, polarization of pump beam, temperature and the use of deuterated materials. The mechanisms, which influence the nonlinear effect in dye-doped liquid crystal films, are also discussed.
MODELING OF INDUCED VOLTAGE OF SILICON DIOXIDE FIBER COUPLING
Authors: HANIM NOR FARIDAH , SAKTIOTO  , ALI JALIL , RAHMAN ROSLY ABDUL
Published: November 2009

This paper describes a new model for the breakdown voltage of SiO 2 fiber coupler using the Pockel effect and empirical equation. The model is evaluated by using the coupling coefficient and the changes in the refractive index. We found that the breakdown voltage is in the order of 102 volt corresponding to coupling coefficient by the order of mm-1. Increasing the value of coupling coefficient between the electrodes leads to a reduction in the breakdown voltage.
THEORETICAL INVESTIGATIONS TO MINIMIZE BIT ERROR RATE BY OPTIMIZING SYSTEM PARAMETERS IN OPTICAL DWDM TRANSMISSION SYSTEMS AT DIFFERENT DATA RATES
Authors: KAUR GURMEET , SINGH M. L. , PATTERH M. S.
Published: November 2009

The amplifier separation and channel separation has conflicting effects on the noise generated due to the fiber non-linear effects (Stimulated Raman scattering SRS and Four wave mixing FWM) and the Amplified spontaneous emission (ASE) noise introduced by inline optical amplifications. While designing an efficient Dense Wavelength Division Multiplexing (DWDM) system, optimization of the channel separation and amplifier separation are required to minimize the non-linear effects (FWM and SRS) along with the ASE noise. In this paper, theoretical investigations of the optical DWDM systems have been presented to minimize the bit error rate (BER) by optimizing inter-channel separation and inter-amplifier separation at different data rates considering the combined effect of SRS, FWM, ASE, receiver and beat noises.
IMPACT OF GEOMETRICAL PARAMETERS ON TRANSMISSION PROPERTIES OF CUT-WIRE PAIR STRUCTURES
Authors: TUNG N. T. , LEE Y. P. , HOAI T. X. , LAM V. D.
Published: November 2009

We investigate the transmission properties of a metamagnetic structure, the so-called cut-wire pair (CWP), using the transfer-matrix method and the finite integration technique. The electric and magnetic resonances of the CWP structure are demonstrated by the effective medium analyses. The corresponding effective permittivity and permeability are calculated from the complex scattering parameters using the standard retrieval procedure. Importantly, the dependence of transmission properties and resonance frequencies on the periodicities as well as the shape of CWP are systematically examined.
Graph annotations in modeling complex network topologies
Authors: Dimitropoulos Xenofontas , Krioukov Dmitri , Vahdat Amin , Riley George
Published: November 2009

The coarsest approximation of the structure of a complex network, such as the Internet, is a simple undirected unweighted graph. This approximation, however, loses too much detail. In reality, objects represented by vertices and edges in such a graph possess some nontrivial internal structure that varies across and differentiates among distinct types of links or nodes. In this work, we abstract such additional information as network
annotations
. We introduce a network topology modeling framework that treats annotations as an extended correlation profile of a network. Assuming we have this profile measured for a given network, we present an algorithm to rescale it in order to construct networks of varying size that still reproduce the original measured annotation profile.

Using this methodology, we accurately capture the network properties essential for realistic simulations of network applications and protocols, or any other simulations involving complex network topologies, including modeling and simulation of network evolution. We apply our approach to the Autonomous System (AS) topology of the Internet annotated with business relationships between ASs. This topology captures the large-scale structure of the Internet. In depth understanding of this structure and tools to model it are cornerstones of research on future Internet architectures and designs. We find that our techniques are able to accurately capture the structure of annotation correlations within this topology, thus reproducing a number of its important properties in synthetically-generated random graphs.
Integrated simulation and optimization for wildfire containment
Authors: Hu Xiaolin , Ntaimo Lewis
Published: November 2009

Wildfire containment is an important but challenging task. The ability to predict fire spread behavior, optimize a plan for firefighting resource dispatch and evaluate such a plan using several firefighting tactics is essential for supporting decision making for containing wildfires. In this article, we present an integrated framework for wildfire spread simulation, firefighting resource optimization and wildfire suppression simulation. We present a stochastic mixed-integer programming model for initial attack to generate firefighting resource dispatch plans using as input fire spread scenario results from a standard wildfire behavior simulator. A new agent-based discrete event simulation model for fire suppression is used to simulate fire suppression based on dispatch plans from the stochastic optimization model, and in turn provides feedback to the optimization model for revising the dispatch plans if necessary. We report on several experimental results, which demonstrate that different firefighting tactics can lead to significantly different fire suppression results for a given dispatch plan, and simulation of these tactics can provide valuable information for fire managers in selecting dispatch plans from optimization models before actual implementation in the field.
Dependence clusters in source code
Authors: Harman Mark , Binkley David , Gallagher Keith , Gold Nicolas , Krinke Jens
Published: November 2009

A dependence cluster is a set of program statements, all of which are mutually inter-dependent. This article reports a large scale empirical study of dependence clusters in C program source code. The study reveals that large dependence clusters are surprisingly commonplace. Most of the 45 programs studied have clusters of dependence that consume more than 10% of the whole program. Some even have clusters consuming 80% or more. The widespread existence of clusters has implications for source code analyses such as program comprehension, software maintenance, software testing, reverse engineering, reuse, and parallelization.
An experimental analysis of self-adjusting computation
Authors: Acar Umut A. , Blelloch Guy E. , Blume Matthias , Harper Robert , Tangwongsan Kanat
Published: November 2009

Recent work on adaptive functional programming (AFP) developed techniques for writing programs that can respond to modifications to their data by performing
change propagation
. To achieve this, executions of programs are represented with
dynamic dependence graphs
(DDGs) that record data dependences and control dependences in a way that a change-propagation algorithm can update the computation as if the program were from scratch, by re-executing only the parts of the computation affected by the changes. Since change-propagation only re-executes parts of the computation, it can respond to certain incremental modifications asymptotically faster than recomputing from scratch, potentially offering significant speedups. Such asymptotic speedups, however, are rare: for many computations and modifications, change propagation is no faster than recomputing from scratch.

In this article, we realize a duality between dynamic dependence graphs and memoization, and combine them to give a change-propagation algorithm that can dramatically increase computation reuse. The key idea is to use DDGs to identify and re-execute the parts of the computation that are affected by modifications, while using memoization to identify the parts of the computation that remain unaffected by the changes. We refer to this approach as self-adjusting computation. Since DDGs are imperative, but (traditional) memoization requires purely functional computation, reusing computation correctly via memoization becomes a challenge. We overcome this challenge with a technique for remembering and reusing not just the results of function calls (as in conventional memoization), but their executions represented with DDGs. We show that the proposed approach is realistic by describing a library for self-adjusting computation, presenting efficient algorithms for realizing the library, and describing and evaluating an implementation. Our experimental evaluation with a variety of applications, ranging from simple list primitives to more sophisticated computational geometry algorithms, shows that the approach is effective in practice: compared to recomputing from-scratch; self-adjusting programs respond to small modifications to their data orders of magnitude faster.
Music-driven character animation
Authors: Sauer Danielle , Yang Yee-Hong
Published: November 2009

Music-driven character animation extracts musical features from a song and uses them to create an animation. This article presents a system that builds a new animation directly from musical attributes, rather than simply synchronizing it to the music like similar systems. Using a simple script that identifies the movements involved in the performance and their timing, the user can easily control the animation of characters. Another unique feature of the system is its ability to incorporate multiple characters into the same animation, both with synchronized and unsynchronized movements. A system that integrates Celtic dance movements is developed in this article. An evaluation of the results shows that the majority of animations are found to be appealing to viewers and that altering the music can change the attractiveness of the final result.
A study of content authentication in proxy-enabled multimedia delivery systems
Authors: Deng Robert H. , Yang Yanjiang
Published: November 2009

Compared with the direct server-user approach, the server-proxy-user architecture for multimedia delivery promises significantly improved system scalability. The introduction of the intermediary transcoding proxies between content servers and end users in this architecture, however, brings unprecedented challenges to content security. In this article, we present a systematic study on the end-to-end content authentication problem in the server-proxy-user context, where intermediary proxies transcode multimedia content dynamically. We present a formal model for the authentication problem, propose a concrete construction for authenticating generic data modality and formally prove its security. We then apply the generic construction to authenticating specific multimedia formats, for example, JPEG2000 code-streams and MPEG-4 video streams. The prototype implementation shows that our scheme is suitable for practical applications.
Randomized fast design of short DNA words
Authors: Kao Ming-Yang , Sanghi Manan , Schweller Robert
Published: November 2009

We consider the problem of efficiently designing sets (codes) of equal-length DNA strings (words) that satisfy certain combinatorial constraints. This problem has numerous motivations including DNA self-assembly and DNA computing. Previous work has extended results from coding theory to obtain bounds on code size for new biologically motivated constraints and has applied heuristic local search and genetic algorithm techniques for code design. This article proposes a natural optimization formulation of the DNA code design problem in which the goal is to design
n
strings that satisfy a given set of constraints while minimizing the length of the strings. For multiple sets of constraints, we provide simple randomized algorithms that run in time polynomial in
n
and any given constraint parameters, and output strings of length within a constant factor of the optimal with high probability. To the best of our knowledge, this work is the first to consider this type of optimization problem in the context of DNA code design.
Automated trust negotiation using cryptographic credentials
Authors: Li Jiangtao , Li Ninghui , Winsborough William H.
Published: November 2009

In automated trust negotiation (ATN), two parties exchange digitally signed credentials that contain attribute information to establish trust and make access control decisions. Because the information in question is often sensitive, credentials are protected according to access control policies. In traditional ATN, credentials are transmitted either in their entirety or not at all. This approach can at times fail unnecessarily, either because a cyclic dependency makes neither negotiator willing to reveal her credential before her opponent because the opponent must be authorized for all attributes packaged together in a credential to receive any of them, or because it is necessary to disclose the precise attribute values, rather than merely proving they satisfy some predicate (such as being over 21 years of age). Recently, several cryptographic credential schemes and associated protocols have been developed to address these and other problems. However, they can be used only as fragments of an ATN process. This article introduces a framework for ATN in which the diverse credential schemes and protocols can be combined, integrated, and used as needed. A policy language is introduced that enables negotiators to specify authorization requirements that must be met by an opponent to receive various amounts of information about certified attributes and the credentials that contain it. The language also supports the use of uncertified attributes, allowing them to be required as part of policy satisfaction, and to place their (automatic) disclosure under policy control.
Keyboard acoustic emanations revisited
Authors: Zhuang Li , Zhou Feng , Tygar J. D.
Published: November 2009

We examine the problem of keyboard acoustic emanations. We present a novel attack taking as input a 10-minute sound recording of a user typing English text using a keyboard and recovering up to 96% of typed characters. There is no need for training recordings labeled with the corresponding clear text. A recognizer bootstrapped from a 10-minute sound recording can even recognize random text such as passwords: In our experiments, 90% of 5-character random passwords using only letters can be generated in fewer than 20 attempts by an adversary; 80% of 10-character passwords can be generated in fewer than 75 attempts by an adversary. In the attack, we use the statistical constraints of the underlying content, English language, to reconstruct text from sound recordings without knowing the corresponding clear text. The attack incorporates a combination of standard machine learning and speech recognition techniques, including cepstrum features, Hidden Markov Models, linear classification, and feedback-based incremental learning.
Enforcing access control in Web-based social networks
Authors: Carminati Barbara , Ferrari Elena , Perego Andrea
Published: November 2009

In this article, we propose an access control mechanism for Web-based social networks, which adopts a rule-based approach for specifying access policies on the resources owned by network participants, and where authorized users are denoted in terms of the type, depth, and trust level of the relationships existing between nodes in the network. Different from traditional access control systems, our mechanism makes use of a semidecentralized architecture, where access control enforcement is carried out client-side. Access to a resource is granted when the requestor is able to demonstrate being authorized to do that by providing a proof. In the article, besides illustrating the main notions on which our access control model relies, we present all the protocols underlying our system and a performance study of the implemented prototype.
Efficient and secure protocols for privacy-preserving set operations
Authors: Sang Yingpeng , Shen Hong
Published: November 2009

Many applications require performing set operations without publishing individual datesets. In this article, we address this problem for five fundamental set operations including set intersection, cardinality of set intersection, element reduction, overthreshold set-union, and subset relation. Our protocols are obtained in the universally composable security framework, in the assumption of the probabilistic polynomial time bounded adversary, which actively controls a fixed set of
t
parties and the assumption of an authenticated broadcast channel. Our constructions utilize building blocks of nonmalleable NonInteractive Zero-Knowledge (NIZK) arguments, which are based on a (
t
+ 1,
N
)-threshold version (
N
is the number of parties in the protocol) of the boneh-goh-nissim (BGN) cryptosystem whose underlying group supports bilinear maps, in the assumption that the public key and shares of the secret key have been generated by a trusted dealer. The previous studies were all based on the stand-alone model with the same assumptions on the adversary, broadcast channel, and key generation. For the first four operations, we propose protocols that improve the previously known results by an
O
(
N
) factor in the computation and communication complexities. For the subset relation, our protocol is the first one secure against the active adversary. Our constructions of NIZK have independent interest in that, though also mentioned as building blocks, the previous work did not illustrate how to construct them. We construct these NIZK with an additional nonmalleable property, the same complexity as claimed in the previous work, and also an improvement on the communication complexity.
Cryptanalysis of the random number generator of the Windows operating system
Authors: Dorrendorf Leo , Gutterman Zvi , Pinkas Benny
Published: November 2009

The PseudoRandom Number Generator (PRNG) used by the Windows operating system is the most commonly used PRNG. The pseudorandomness of the output of this generator is crucial for the security of almost any application running in Windows. Nevertheless, its exact algorithm was never published.

We examined the binary code of a distribution of Windows 2000. This investigation was done without any help from Microsoft. We reconstructed the algorithm used by the pseudorandom number generator (namely, the function CryptGenRandom). We analyzed the security of the algorithm and found a nontrivial attack: Given the internal state of the generator, the previous state can be computed in 2
23
steps. This attack on forward security demonstrates that the design of the generator is flawed, since it is well known how to prevent such attacks. After our analysis was published, Microsoft acknowledged that Windows XP is vulnerable to the same attack.

We also analyzed the way in which the generator is used by the operating system and found that it amplifies the effect of the attack: The generator is run in user mode rather than in kernel mode; therefore, it is easy to access its state even without administrator privileges. The initial values of part of the state of the generator are not set explicitly, but rather are defined by whatever values are present on the stack when the generator is called. Furthermore, each process runs a different copy of the generator, and the state of the generator is refreshed with system-generated entropy only after generating 128KB of output for the process running it. The result of combining this observation with our attack is that learning a single state may reveal 128KB of the past and future output of the generator.

The implication of these findings is that a buffer overflow attack or a similar attack can be used to learn a single state of the generator, which can then be used to predict all random values, such as SSL keys, used by a process in all its past and future operations. This attack is more severe and more efficient than known attacks in which an attacker can only learn SSL keys if it is controlling the attacked machine at the time the keys are used.
Finitary winning in ω-regular games
Authors: Chatterjee Krishnendu , Henzinger Thomas A. , Horn Florian
Published: November 2009

Games on graphs with ω-regular objectives provide a model for the control and synthesis of reactive systems. Every ω-regular objective can be decomposed into a safety part and a liveness part. The liveness part ensures that something good happens “eventually.” Two main strengths of the classical, infinite-limit formulation of liveness are robustness (independence from the granularity of transitions) and simplicity (abstraction of complicated time bounds). However, the classical liveness formulation suffers from the drawback that the time until something good happens may be unbounded. A stronger formulation of liveness, so-calledfinitaryliveness, overcomes this drawback, while still retaining robustness and simplicity. Finitary liveness requires that there exists an unknown, fixed boundbsuch that something good happens withinbtransitions. While for one-shot liveness (reachability) objectives, classical and finitary liveness coincide, for repeated liveness (Büchi) objectives, the finitary formulation is strictly stronger. In this work we study games with finitary parity and Streett objectives. We prove the determinacy of these games, present algorithms for solving these games, and characterize the memory requirements of winning strategies. We show that finitary parity games can be solved in polynomial time, which is not known for infinitary parity games. For finitary Streett games, we give an EXPTIME algorithm and show that the problem is NP-hard. Our algorithms can be used, for example, for synthesizing controllers that do not let the response time of a system increase without bound.
Higher-order term indexing using substitution trees
Authors: Pientka Brigitte
Published: November 2009

We present a higher-order term indexing strategy based on substitution trees for simply typed lambda-terms. There are mainly two problems in adapting first-order indexing techniques. First, many operations used in building an efficient term index and retrieving a set of candidate terms from a large collection are undecidable in general for higher-order terms. Second, the scoping of variables and binders in the higher-order case presents challenges.

The approach taken in this article is to reduce the problem to indexing linear higher-order patterns, a decidable fragment of higher-order terms, and delay solving terms outside of this fragment. We present insertion of terms into the index based on computing the most specific linear generalization of two linear higher-order patterns, and retrieval based on matching two linear higher-order patterns. Our theoretical framework maintains that terms are in βη-normal form, thereby eliminating the need to renormalize and raise terms during insertion and retrieval. Finally, we prove correctness of our presented algorithms. This indexing structure is implemented as part of the Twelf system to speed up the execution of the tabled higher-logic programming interpreter.
A general framework for sound and complete Floyd-Hoare logics
Authors: Arthan Rob , Martin Ursula , Mathiesen Erik A. , Oliva Paulo
Published: November 2009

This article presents an abstraction of Hoare logic to traced symmetric monoidal categories, a very general framework for the theory of systems. Our abstraction is based on a traced monoidal functor from an arbitrary traced monoidal category into the category of preorders and monotone relations. We give several examples of how our theory generalizes usual Hoare logics (partial correctness of while programs, partial correctness of pointer programs), and provide some case studies on how it can be used to develop new Hoare logics (runtime analysis of while programs and stream circuits).