bluuebunny/crossref_metadata_2025 huggingface dataset:
Special-Purpose Hardware for Solving the Elliptic Curve Discrete Logarithm Problem
Authors: Güneysu Tim , Paar Christof , Pelzl Jan
Published: January 2009

The resistance against powerful index-calculus attacks makes Elliptic Curve Cryptosystems (ECC) an interesting alternative to conventional asymmetric cryptosystems, like RSA. Operands in ECC require significantly less bits at the same level of security, resulting in a higher computational efficiency compared to RSA. With growing computational capabilities and continuous technological improvements over the years, however, the question of the security of ECC against attacks based on special-purpose hardware arises. In this context, recently emerged low-cost FPGAs demand for attention in the domain of hardware-based cryptanalysis: the extraordinary efficiency of modern programmable hardware devices allow for a low-budget implementation of hardware-based ECC attacks---without the requirement of the expensive development of ASICs.

With focus on the aspect of cost-efficiency, this contribution presents and analyzes an FPGA-based architecture of an attack against ECC over prime fields. A multi-processing hardware architecture for Pollard's Rho method is described. We provide results on actually used key lengths of ECC (128 bits and above) and estimate the expected runtime for a successful attack.

As a first result, currently used elliptic curve cryptosystems with a security of 160 bit and above turn out to be infeasible to break with available computational and financial resources. However, some of the security standards proposed by the Standards for Efficient Cryptography Group (SECG) become subject to attacks based on low-cost FPGAs.
Mercury BLASTP
Authors: Jacob Arpith , Lancaster Joseph , Buhler Jeremy , Harris Brandon , Chamberlain Roger D.
Published: January 2009

Large-scale protein sequence comparison is an important but compute-intensive task in molecular biology. BLASTP is the most popular tool for comparative analysis of protein sequences. In recent years, an exponential increase in the size of protein sequence databases has required either exponentially more running time or a cluster of machines to keep pace. To address this problem, we have designed and built a high-performance FPGA-accelerated version of BLASTP,
Mercury BLASTP
. In this article, we describe the architecture of the portions of the application that are accelerated in the FPGA, and we also describe the integration of these FPGA-accelerated portions with the existing BLASTP software. We have implemented Mercury BLASTP on a commodity workstation with two Xilinx Virtex-II 6000 FPGAs. We show that the new design runs 11--15 times faster than software BLASTP on a modern CPU while delivering close to 99% identical results.
Parametric Yield Modeling and Simulations of FPGA Circuits Considering Within-Die Delay Variations
Authors: Sedcole Pete , Cheung Peter Y. K.
Published: January 2009

Variations in the semiconductor fabrication process results in differences in parameters between transistors on the same die, a problem exacerbated by lithographic scaling. Field-Programmable Gate Arrays may be able to compensate for within-die delay variability, by judicious use of reconfigurability. This article presents two strategies for compensating within-die stochastic delay variability by using reconfiguration: reconfiguring the entire FPGA, and relocating subcircuits within an FPGA. Analytical models for the theoretical bounds on the achievable gains are derived for both strategies and compared to models for worst-case design as well as statistical static timing analysis (SSTA). All models are validated by comparison to circuit-level Monte Carlo simulations. It is demonstrated that significant improvements in circuit yield and timing are possible using SSTA alone, and these improvements can be enhanced by employing reconfiguration-based techniques.
Multivariate Gaussian Random Number Generation Targeting Reconfigurable Hardware
Authors: Thomas David B. , Luk Wayne
Published: January 2009

The multivariate Gaussian distribution is often used to model correlations between stochastic time-series, and can be used to explore the effect of these correlations across
N
time-series in Monte-Carlo simulations. However, generating random correlated vectors is an
O
(
N
2
) process, and quickly becomes a computational bottleneck in software simulations. This article presents an efficient method for generating vectors in parallel hardware, using
N
parallel pipelined components to generate a new vector every
N
cycles. This method maps well to the embedded block RAMs and multipliers in contemporary FPGAs, particularly as extensive testing shows that the limited bit-width arithmetic does not reduce the statistical quality of the generated vectors. An implementation of the architecture in the Virtex-4 architecture achieves a 500MHz clock-rate, and can support vector lengths up to 512 in the largest devices. The combination of a high clock-rate and parallelism provides a significant performance advantage over conventional processors, with an xc4vsx55 device at 500MHz providing a 200 times speedup over an Opteron 2.6GHz using an AMD optimised BLAS package. In a case study in Delta-Gamma Value-at Risk, an RC2000 accelerator card using an xc4vsx55 at 400MHz is 26 times faster than a quad Opteron 2.6GHz SMP.
On the trade-off between power and flexibility of FPGA clock networks
Authors: Lamoureux Julien , Wilton Steven J. E.
Published: January 2009

FPGA clock networks consume a significant amount of power, since they toggle every clock cycle and must be flexible enough to implement the clocks for a wide range of different applications. The efficiency of FPGA clock networks can be improved by reducing this flexibility; however, reducing the flexibility introduces stricter constraints during the clustering and placement stages of the FPGA CAD flow. These constraints can reduce the overall efficiency of the final implementation. This article examines the trade-off between the power consumption and flexibility of FPGA clock networks.

Specifically, this article makes three contributions. First, it presents a new parameterized clock-network framework for describing and comparing FPGA clock networks. Second, it describes new clock-aware placement techniques that are needed to find a legal placement satisfying the constraints imposed by the clock network. Finally, it performs an empirical study to examine the trade-off between the power consumption of the clock network and the impact of the CAD constraints for a number of different clock networks with varying amounts of flexibility.

The results show that the techniques used to produce a legal placement can have a significant influence on power and the ability of the placer to find a legal solution. On average, circuits placed using the most effective techniques dissipate 5% less overall energy and are significantly more likely to be legal than circuits placed using other techniques. Moreover, the results show that the architecture of the clock network is also important. On average, FPGAs with an efficient clock network are up to 14.6% more energy efficient compared to other FPGAs.
An open-source HyperTransport core
Authors: Slogsnat David , Giese Alexander , Nüssle Mondrian , Brüning Ulrich
Published: January 2009

This article presents the design of a generic HyperTransport (HT) core. HyperTransport is a packet-based interconnect technology for low-latency, high-bandwidth point-to-point connections. It is specially optimized to achieve a very low latency. The core has been verified in system using an FPGA. This exhaustive verification and the generic design allow the mapping to both ASICs and FPGAs. The implementation described in this work supports a 16-bit link width, as used by Opteron processors. On a Xilinx Virtex-4 FX60, the core supports a link frequency of 400 MHz DDR and offers a maximum bidirectional bandwidth of 3.2GB/s. The in-system verification has been performed using a custom FPGA board that has been plugged into a HyperTransport extension connector (HTX) of a standard Opteron-based motherboard. HTX slots in Opteron-based motherboards allow very high-bandwidth, low-latency communication, since the HTX device is directly connected to one of the HyperTransport links of the processor. Performance analysis shows a unidirectional payload bandwidth of 1.4GB/s and a read latency of 180 ns. The HT core in combination with the HTX board is an ideal base for prototyping systems and implementing FPGA coprocessors. The HT core is available as open source.
Particle graphics on reconfigurable hardware
Authors: Beeckler John S. , Gross Warren J.
Published: January 2009

Particle graphics simulations are well suited for modeling complex phenomena such as water, cloth, explosions, fire, smoke, and clouds. They are normally realized in software as part of an interactive graphics application. The computational complexity of particle graphics simulations restricts the number of particles that can be updated in software at interactive frame rates. This article presents the design and implementation of a hardware particle graphics engine for accelerating real-time particle graphics simulations. We explore the design process, implementation issues, and limitations of using field-programmable gate arrays (FPGAs) for the acceleration of particle graphics. The FPGA particle engine processes million-particle systems at a rate from 47 to 112 million particles per second, which represents one to two orders of magnitude speedup over a 2.8 GHz CPU. Using three FPGAs, a maximum sustained performance of 112 million particles per second was achieved.
Perturb+mutate
Authors: Grant David , Lemieux Guy
Published: January 2009

CAD tool designers are always searching for more benchmark circuits to stress their software. In this article we present a heuristic method to generate benchmark circuits specially suited for incremental place-and-route tools. The method removes part of a real circuit and replaces it with an altered version of the same circuit to mimic an incremental design change. The alteration consists of two steps:
mutate
followed by
perturb
. The perturb step exactly preserves as many circuit characteristics as possible. While perturbing, reproduction of interconnect locality, a characteristic that is difficult to measure reliably or reproduce exactly, is controlled using a new technique,
ancestor depth control
(ADC). Perturbing with ADC produces circuits with postrouting properties that match the best techniques known to-date. The mutate step produces targetted mutations resulting in controlled changes to specific circuit properties (while keeping other properties constant). We demonstrate one targetted mutation heuristic, scale, to significantly change circuit size with little change to other circuit characteristics. The method is simple enough for inclusion in a CAD tool directly, and fast enough for use in on-the-fly benchmark generation.
Perfecto
Authors: Hsiung Pao-Ann , Lin Chao-Sheng , Liao Chih-Feng
Published: January 2009

To cope with increasing demands for higher computational power and greater system flexibility, dynamically and partially reconfigurable logic has started to play an important role in embedded systems and systems-on-chip (SoC). However, when using traditional design methods and tools, it is difficult to estimate or analyze the performance impact of including such reconfigurable logic devices into a system design. In this work, we present a system-level framework, called Perfecto, which is able to perform rapid exploration of different reconfigurable design alternatives and to detect system performance bottlenecks. This framework is based on the popular IEEE standard system-level design language SystemC, which is supported by most EDA and ESL tools. Given an architecture model and an application model, Perfecto uses SystemC
transaction-level models
(TLMs) to simulate the system design alternatives automatically. Different hardware-software copartitioning, coscheduling, and placement algorithms can be embedded into the framework for analysis; thus, Perfecto can also be used to design the algorithms to be used in an operating system for reconfigurable systems. Applications to a simple illustration example and a network security system have shown how Perfecto helps a designer make intelligent partition decisions, optimize system performance, and evaluate task placements.
Ubiquitous Accessibility, Common Technology Core, and Micro Assistive Technology
Authors: Vanderheiden Gregg C.
Published: January 2009

Much has changed since 1992 when the original CACM article by Ephraim Glinert and Bryant York was published. In the early 1990's, accessibility was mostly an add-on, with only Apple computers having built-in access. Computers were playing an increasingly important role in education and employment, but had not yet completely integrated themselves into all aspects of life as completely as they have today. The World Wide Web as we know it had not yet been born. Today there are accessibility features built directly into every major operating system, and one OS even includes a built-in screen reader. Assistive technologies are more numerous and capable. And awareness of the importance of access is much higher. However, some things have not changed. Assistive technologies lag behind mainstream technologies in both compatibility and functionality. Effective assistive technologies are often beyond the financial reach of those who need them. Effective assistive technologies are not available in many countries and many languages, even though technology is reaching into education, employment, and daily living of more countries and more people in each country every year. In moving forward we need to build on what we have achieved and explore new concepts, such as a
common technical core, ubiquitous accessibility, micro assistive technology
, and
free public accessibility
. Cooperative and collaborative approaches also need to be explored if we are to have any hope of catching up and keeping up with the ever-accelerating mainstream information and communication technologies.
Access and Empowerment
Authors: Ladner Richard E.
Published: January 2009

A number of positive changes have taken place since Glinert and York's 1992 call-to-arms. Progress reviewed in this article includes evolving considerations of universal design in the marketplace, ubiquitous computing with accessibility features, increasing computing research and conference venues that address needs of users with disabilities, and attention to the importance of user empowerment in development.
Multimodal Trajectory Playback for Teaching Shape Information and Trajectories to Visually Impaired Computer Users
Authors: Crossan Andrew , Brewster Stephen
Published: January 2009

There are difficulties in presenting nontextual or dynamic information to blind or visually impaired users through computers. This article examines the potential of haptic and auditory trajectory playback as a method of teaching shapes and gestures to visually impaired people. Two studies are described which test the success of teaching simple shapes. The first study examines haptic trajectory playback alone, played through a force-feedback device, and compares performance of visually impaired users with sighted users. It demonstrates that the task is significantly harder for visually impaired users. The second study builds on these results, combining force-feedback with audio to teach visually impaired users to recreate shapes. The results suggest that users performed significantly better when presented with multimodal haptic and audio playback of the shape, rather than haptic only. Finally, an initial test of these ideas in an application context is described, with sighted participants describing drawings to visually impaired participants through touch and sound. This study demonstrates in what situations trajectory playback can prove a useful role in a collaborative setting.
Modeling light scattering for virtual heritage
Authors: Gutierrez Diego , Sundstedt Veronica , Gomez Fermin , Chalmers Alan
Published: January 2009

Computer graphics, in particular high-fidelity rendering, make it possible to recreate cultural heritage on a computer, including a precise lighting simulation. Achieving maximum accuracy is of the highest importance when investigating how a site might have appeared in the past. Failure to use such high fidelity means there is a very real danger of misrepresenting the past. Although we can accurately simulate the propagation of light in the environment, little work has been undertaken into the effect that light scattering due to participating media (such as dust in the atmosphere) has on the perception of the site. In this article, we present the high-fidelity rendering pipeline including participating media. We also investigate how the appearance of an archaeological reconstruction is affected when dust is included in the simulation. The chosen site for our study is the ancient Egyptian temple of Kalabsha.
Using survival analysis on conservation metadata to benchmark treatment frequency
Authors: Hutchings Jeremy , Smith Jonathan Ashley
Published: January 2009

This research addresses the question of what is an acceptable period between conservation treatments. Taking the cleaning of impressionist paintings as a case study, survival analysis is carried out on metadata from conservation records for the Tate, UK, the National Gallery in Oslo, Norway, and the National Trust, UK. Currently the only guidance available is offered by the National Trust. Based on cost-benefit analysis, it suggests an interval of 25 years for light surface cleaning and 100 years for major treatment. The majority of paintings held by the National Trust are pre-20th century, with a varnish layer protecting the paint surface. Arguments are put forward that this guidance cannot be applied to unvarnished paintings with exposed ground and a fragile paint layer. The cleaning process for these types of paintings poses a greater risk as it inevitably causes some loss of paint. Any cleaning of paintings in this category is more akin to a major conservation treatment. The Kaplan Meier Product Limit estimator uses metadata collected from the conservation records to estimate an average inter-cleaning period for the Tate, UK, and National Gallery, Oslo. The result of the theoretical analysis, although highly dependent on the quality of conservation records available, is supplemented by evidence from practical experience. Current views on acceptable frequency of cleaning and the associated risks of treatment are sought using a survey of conservators with experience of treating impressionist and post-impressionist paintings. This is applied to a case study of the Munch paintings in the University Aula, Oslo, that are currently unacceptably dirty. In the past, these paintings have been cleaned on average once every 14 years, which is clearly too often. The results suggest that the intercleaning period should be increased by a factor of three. Criteria are discussed for improving the environment within the University Aula, Oslo, to achieve this goal.
Islamic geometrical patterns indexing and classification using discrete symmetry groups
Authors: Djibril Mohamed Ould , Thami Rachid Oulad Haj
Published: January 2009

In this article, we propose a general computational model for the extraction of symmetry features of Islamic geometrical patterns' (IGP) images. We describe IGP images using the discrete symmetry groups theory. Our model contains the three following steps. (1) By noting that these patterns fall into three major categories, we begin our indexation process by classifying every pattern into one of these categories. The first pattern category describes all the patterns generated by translation along one direction. Every pattern of this category can be classified into one of the seven Frieze groups. The second type of pattern contains translational symmetries in two independent directions. Patterns of this category can be classified into one of the seventeen Wallpaper groups. The last type, called rosettes, describes patterns which begin at a central point and grow radially outward. We use rosette symmetry groups to classify patterns of this latter category. (2) For every pattern, we extract the symmetry features, namely, the symmetry group and the fundamental region, which is a representative region in the image from which the whole image can be regenerated. But for rosette groups, we can also compute the number of folds. (3) Finally, we describe the fundamental region by a simple color histogram and build the feature vector which is a combination of the symmetry feature (defined in the second step) and histogram information. Experiments show promising results for either IGP images' classification or indexing. Efforts for the subsequent task of classifying Islamic geometrical patterns' images can be significantly reduced.
Exploring cultural heritage sites through space and time
Authors: Laycock R. G. , Drinkwater D. , Day A. M.
Published: January 2009

Traveling through a single virtual environment only tells part of the story; a particularly interesting aspect is to illustrate how an area has developed over time. This article presents a unified approach to illustrating four-dimensional data concerning a cultural heritage site. The proposed framework provides a semi-automatic approach to both reconstructing the environment and bringing all the time-dependent models into an intuitive visualization package. For each time period considered for reconstruction, the system requires a set of building footprint maps depicting the layout of the environment plus a few statistics. The statistics govern the construction of three-dimensional building models, allowing each building's architectural style, typical building height, and roof style to be altered. This information is automatically processed and converted into a form that can be visualized. By integrating high quality landmark buildings from laser scanning or interactive modelling packages into the automatically generated scene, the cultural heritage site is realized both in a spatial and temporal context. The visualization is achieved via a 4D navigable movie which is presented using two concrete implementations written using Flash and OpenGL. The OpenGL-based implementation allows a collection of 3DS Max scenes to be automatically visualized requiring only a set of camera paths identified by the user.
XPath leashed
Authors: Benedikt Michael , Koch Christoph
Published: January 2009

This survey gives an overview of formal results on the XML query language XPath. We identify several important fragments of XPath, focusing on subsets of XPath 1.0. We then give results on the expressiveness of XPath and its fragments compared to other formalisms for querying trees, algorithms, and complexity bounds for evaluation of XPath queries, as well as static analysis of XPath queries.
Solving problems on recursively constructed graphs
Authors: Borie Richard B. , Parker R. Gary , Tovey Craig A.
Published: January 2009

Fast algorithms can be created for many graph problems when instances are confined to classes of graphs that are recursively constructed. This article first describes some basic conceptual notions regarding the design of such fast algorithms, and then the coverage proceeds through several recursive graph classes. Specific classes include trees, series-parallel graphs,k-terminal graphs, treewidth-kgraphs,k-trees, partialk-trees,k-jackknife graphs, pathwidth-kgraphs, bandwidth-kgraphs, cutwidth-kgraphs, branchwidth-kgraphs, Halin graphs, cographs, cliquewidth-kgraphs,k-NLC graphs,k-HB graphs, and rankwidth-kgraphs. The definition of each class is provided. Typical algorithms are applied to solve problems on instances of most classes. Relationships between the classes are also discussed.
Multiparty nonrepudiation
Authors: Onieva Jose A. , Zhou Jianying , Lopez Javier
Published: January 2009

Nonrepudiation is a security service that plays an important role in many Internet applications. Traditional two-party nonrepudiation has been studied intensively in the literature. This survey focuses on multiparty scenarios and provides a comprehensive overview. It starts with a brief introduction of fundamental issues on nonrepudiation, including the types of nonrepudiation service and cryptographic evidence, the roles of trusted third-party, nonrepudiation phases and requirements, and the status of standardization. Then it describes the general multiparty nonrepudiation problem, and analyzes state-of-the-art mechanisms. After this, it presents in more detail the 1-N multiparty nonrepudiation solutions for distribution of different messages to multiple recipients. Finally, it discusses advanced solutions for two typical multiparty nonrepudiation applications, namely, multiparty certified email and multiparty contract signing.
Survey and analysis of multimodal sensor planning and integration for wide area surveillance
Authors: Abidi Besma R. , Aragam Nash R. , Yao Yi , Abidi Mongi A.
Published: January 2009

Although sensor planning in computer vision has been a subject of research for over two decades, a vast majority of the research seems to concentrate on two particular applications in a rather limited context of laboratory and industrial workbenches, namely 3D object reconstruction and robotic arm manipulation. Recently, increasing interest is engaged in research to come up with solutions that provide wide-area autonomous surveillance systems for object characterization and situation awareness, which involves portable, wireless, and/or Internet connected radar, digital video, and/or infrared sensors. The prominent research problems associated with multisensor integration for wide-area surveillance are modality selection, sensor planning, data fusion, and data exchange (communication) among multiple sensors. Thus, the requirements and constraints to be addressed include far-field view, wide coverage, high resolution, cooperative sensors, adaptive sensing modalities, dynamic objects, and uncontrolled environments. This article summarizes a new survey and analysis conducted in light of these challenging requirements and constraints. It involves techniques and strategies from work done in the areas of sensor fusion, sensor networks, smart sensing, Geographic Information Systems (GIS), photogrammetry, and other intelligent systems where finding optimal solutions to the placement and deployment of multimodal sensors covering a wide area is important. While techniques covered in this survey are applicable to many wide-area environments such as traffic monitoring, airport terminal surveillance, parking lot surveillance, etc., our examples will be drawn mainly from such applications as harbor security and long-range face recognition.
Interview with Cathy Marshall
Authors: Atzenbeck Claus
Published: January 2009

Cathy Marshall is a Senior Researcher at Microsoft Research, Silicon Valley; she has contributed to both the product and research divisions at Microsoft. Cathy has long worked in the disciplinary interstices of computer science, information science, and the humanities, with occasional collaborations in art and the sciences; one of the original members of the Xerox NoteCards project, she was drawn to the Hypertext Community when it first formed in 1987. She went on to develop Aquanet (with Frank Halasz, Russ Rogers, and Bill Janssen) and VIKI (with Frank Shipman and Jim Coombs). Her experiences with Aquanet led her to coin the term "information farming." In 2003, she served as the Program Chair of the ACM/IEEE Joint Conference on Digital Libraries; she has also served as the Program co-Chair of Hypertext 1996 and JCDL 2006. Cathy won the Hypertext conference's best paper award in 1998 and 1999, and the JCDL best paper award in 1998 and 2008. She has delivered keynotes at WWW, Hypertext, Usenix FAST, CNI, IVICA, ACH-ALLC, and a variety of other CS and LIS venues. Her homepages are: http://www.csdl.tamu.edu/~marshall and http://research.microsoft.com/~cathymar.
The very small world of the well-connected
Authors: Shi Xiaolin , Bonner Matthew , Adamic Lada , Gilbert Anna C.
Published: January 2009

Online networks occupy an increasingly larger position in how we acquire information, how we communicate with one another, and how we disseminate information. Frequently, small sets of vertices dominate various graph and statistical properties of these networks and, because of this, they are relevant for structural analysis and efficient algorithms and engineering. For the web overall, and specifically for social linking in blogs and instant messaging, we provide a principled, rigorous study of the properties, the construction, and the utilization of subsets of special vertices in large online networks. We show that graph synopses defined by the importance of vertices provide small, relatively accurate portraits, independent of the importance measure, of the larger underlying graphs and of the important vertices. Furthermore, they can be computed relatively efficiently.
An epistemic dynamic model for tagging systems
Authors: Dellschaft Klaas , Staab Steffen
Published: January 2009

In recent literature, several models were proposed for reproducing and understanding the tagging behavior of users. They all assume that the tagging behavior is influenced by the previous tag assignments of other users. But they are only partially successful in reproducing characteristic properties found in tag streams. We argue that this inadequacy of existing models results from their inability to include user's background knowledge into their model of tagging behavior. This paper presents a generative tagging model that integrates both components, the background knowledge and the influence of previous tag assignments. Our model successfully reproduces characteristic properties of tag streams. It even explains effects of the user interface on the tag stream.
Up and coming SIGWEB supported conferences
Authors: Deshpande Yogesh
Published: January 2009

SIGWEB supports several specialized conferences, short courses, and workshops, as well as the Annual Hypertext Conference. SIGWEB sponsored conferences focus on timely topics in applied and computational hypertext and Web disciplines and provide a place for members and the entire applied Hypermedia and Web community to exchange ideas and to meet with and expand their network of colleagues. In this article, we provide a brief overview of SIGWEB sponsored conferences, in addition to events that are in cooperation with SIGWEB.
Feature-preserved sampling over streaming data
Authors: Chuang Kun-Ta , Chen Hung-Leng , Chen Ming-Syan
Published: January 2009

In this article, we explore a novel sampling model, calledfeature preserved sampling(FPS) that sequentially generates a high-quality sample over sliding windows. The sampling quality we consider refers to the degree of consistency between the sample proportion and the population proportion of each attribute value in a window. Due to the time-variant nature of real-world datasets, users are more likely to be interested in the most recent data. However, previous works have not been able to generate a high-quality sample over sliding windows that precisely preserves up-to-date population characteristics. Motivated by this shortcoming, we have developed theFPSalgorithm, which has several advantages: (1) it sequentially generates a sample from a time-variant data source over sliding windows; (2) the execution time ofFPSis linear with respect to the database size; (3) therelativeproportional differences between the sample proportions and population proportions of most distinct attribute values are guaranteed to be below a specified error threshold, ε, while therelativeproportion differences of the remaining attribute values are as close to ε as possible, which ensures that the generated sample is of high quality; (4) the sample rate is close to the user specified rate so that a high quality sampling result can be obtained without increasing the sample size; (5) by a thorough analytical and empirical study, we prove thatFPShas acceptable space overheads, especially when the attribute values have Zipfian distributions, andFPScan also excellently preserve the population proportion of multivariate features in the sample; and (6)FPScan be applied to infinite streams and finite datasets equally, and the generated samples can be used for various applications. Our experiments on both real and synthetic data validate thatFPScan effectively obtain a high quality sample of the desired size. In addition, while using the sample generated byFPSin various mining applications, a significant improvement in efficiency can be achieved without compromising the model's precision.
Weighted cluster ensembles
Authors: Domeniconi Carlotta , Al-Razgan Muna
Published: January 2009

Cluster ensembles offer a solution to challenges inherent to clustering arising from its ill-posed nature. Cluster ensembles can provide robust and stable solutions by leveraging the consensus across multiple clustering results, while averaging out emergent spurious structures that arise due to the various biases to which each participating algorithm is tuned. In this article, we address the problem of combining multiple
weighted clusters
that belong to different subspaces of the input space. We leverage the diversity of the input clusterings in order to generate a consensus partition that is superior to the participating ones. Since we are dealing with weighted clusters, our consensus functions make use of the weight vectors associated with the clusters. We demonstrate the effectiveness of our techniques by running experiments with several real datasets, including high-dimensional text data. Furthermore, we investigate in depth the issue of diversity and accuracy for our ensemble methods. Our analysis and experimental results show that the proposed techniques are capable of producing a partition that is as good as or better than the best individual clustering.
On domination game analysis for microeconomic data mining
Authors: Zhang Zhenjie , Lakshmanan Laks V. S. , Tung Anthony K. H.
Published: January 2009

Game theory is a powerful tool for analyzing the competitions among manufacturers in a market. In this article, we present a study on combining game theory and data mining by introducing the concept of domination game analysis. We present a multidimensional market model, where every dimension represents one attribute of a commodity. Every product or customer is represented by a point in the multidimensional space, and a product is said to “dominate” a customer if all of its attributes can satisfy the requirements of the customer. The expected market share of a product is measured by the expected number of the buyers in the customers, all of which are equally likely to buy any product dominating him. A Nash equilibrium is a configuration of the products achieving stable expected market shares for all products. We prove that Nash equilibrium in such a model can be computed in polynomial time if every manufacturer tries to modify its product in a round robin manner. To further improve the efficiency of the computation, we also design two algorithms for the manufacturers to efficiently find their best response to other products in the market.
Scaling in Games & Virtual Worlds
Authors: Waldo Jim
Published: January 2009

I used to be a systems programmer, working on infrastructure used by banks, telecom companies, and other engineers. I worked on operating systems. I worked on distributed middleware. I worked on programming languages. I wrote tools. I did all of the things that hard-core systems programmers do.
Better Scripts, Better Games
Authors: White Walker , Koch Christoph , Gehrke Johannes , Demers Alan
Published: January 2009

The video game industry earned $8.85 billion in revenue in 2007, almost as much as movies made at the box office. Much of this revenue was generated by blockbuster titles created by large groups of people. Though large development teams are not unheard of in the software industry, game studios tend to have unique collections of developers. Software engineers make up a relatively small portion of the game development team, while the majority of the team consists of content creators such as artists, musicians, and designers.
Code Spelunking Redux
Authors: Neville-Neil George V.
Published: January 2009

It has been five years since I first wrote about code spelunking, and though systems continue to grow in size and scope, the tools we use to understand those systems are not growing at the same rate. In fact, I believe we are steadily losing ground. So why should we go over the same ground again? Is this subject important enough to warrant two articles in five years? I believe it is.
Porous pSiCOH Ultralow-k Dielectrics for Chip Interconnects Prepared by PECVD
Authors: Grill Alfred
Published: January 2009

Porous pSiCOH materials with ultralow dielectric constants (ulk) have been developed with dielectric constants reaching values below 2.0. The pSiCOH films, composed of Si, C, O, and H atoms, are prepared by plasma-assisted chemical vapor deposition (PECVD), showing that PECVD can be used to prepare porous materials. The pSiCOH films are deposited as dual-phase materials, and the porosity is formed in them by curing the as-deposited films by thermal anneals, electron beams, or UV irradiation. The porous pSiCOH dielectrics are suitable for integration in the interconnects of VLSI chips of the 45-nm-and-beyond technology nodes, and films with dielectric constants of 2.4 have already been implemented in upcoming 45-nm products. This review discusses the fabrication of pSiCOH films and the characterization of their structure, porosity, and electrical and mechanical properties. The limitations of some of the characterization techniques of these amorphous thin films are also addressed.
Bargaining Failures and Civil War
Authors: Walter Barbara F.
Published: January 2009

This article explores the many bargaining failures that may occur at every stage in intrastate disputes: before fighting breaks out, as a war is being fought, and once a war ends. It argues that disputes that occur within states are particularly susceptible to information and commitment problems. It also reveals why certain countries have more difficulty overcoming these problems than others do. This represents the most comprehensive overview to date of bargaining failures associated with civil wars.
Metabolic fate of plasma glucose during hyperglycemia in impaired glucose tolerance: evidence for further early defects in the pathogenesis of type 2 diabetes
Authors: Bokhari Syed , Emerson Peter , Israelian Zarmen , Gupta Anchal , Meyer Christian
Published: January 2009

We examined the intracellular metabolic fate of plasma glucose during a hyperglycemic clamp in impaired glucose-tolerant (IGT; n = 21) and normal glucose-tolerant subjects ( n = 10) using a combination of [3-3H]glucose infusion with measurement of [3H]water formation and indirect calorimetry. IGT was associated with ∼35% reduced first-phase insulin responses, normal second-phase insulin response, and 25–30% reduced insulin sensitivity, resulting in ∼35% reduced plasma glucose disposal. This was coupled with ∼55% reduced storage of plasma glucose ( P < 0.01) and ∼15–20% reduced glycolysis of plasma glucose ( P < 0.03), accounting for ∼75 and 25% of the reduction in glucose disposal, respectively. Decreased glucose oxidation accounted for virtually all the decrease in glycolysis. Therefore, nonoxidative glycolysis of plasma glucose in IGT was similar to that in NGT ( P > 0.9) and accounted for an increased proportion of systemic glucose disposal ( P < 0.05). We conclude that, in IGT, decreased disposal of plasma glucose involves mainly decreased glycogen synthesis and to a lesser extent decreased glycolysis, which is accounted for by decreased glucose oxidation. An increased proportion of plasma glucose hence undergoes nonoxidative glycolysis, representing a novel early abnormality in the pathogenesis of T2DM.
Effects of type I interferons on IGF-mediated autocrine/paracrine growth of human neuroendocrine tumor cells
Authors: Vitale Giovanni , van Koetsveld Peter M. , de Herder Wouter W. , van der Wansem Katy , Janssen Joop A. M. J. L. , Colao Annamaria , Lombardi Gaetano , Lamberts Steven W. J. , Hofland Leo J.
Published: January 2009

We recently demonstrated that interferon (IFN)-β has a more potent antitumor activity than IFN-α in BON cells, a neuroendocrine tumor (NET) cell line. The present study showed the role of type I IFNs in the modulation of the insulin-like growth factor (IGF) system in NETs. BON cells expressed IGF-I, IGF-II, IGF-I receptor, and insulin receptor mRNA. In addition, IGF-I and IGF-II stimulated the proliferation of BON cells and induced an inhibition of DNA fragmentation (apoptosis). As evaluated by quantitative RT-PCR, treatment with IFN-α (100 IU/ml) or IFN-β (100 IU/ml) inhibited the expression of IGF-II mRNA (−42% and −65%, respectively, both P < 0.001), whereas IGF-I receptor mRNA was significantly upregulated by IFN-α (+28%, P < 0.001) and downregulated by IFN-β (−47%, P < 0.001). Immunoreactive IGF-II concentration decreased in the conditioned medium during IFN-α (−16%, P < 0.05) and IFN-β (−69%, P < 0.001) treatment. Additionally, IGF-I receptor bioactivity was reduced (−54%) after IFN-β treatment. Scatchard analysis of 125I-labeled IGF-I binding to cell membrane of BON cells revealed a dramatic suppression of maximum binding capacity only in the presence of IFN-β. Finally, the proapoptotic activity of IFN-β was partially counteracted by the coadministration of IGF-I and IGF-II (both at 50 nM). In conclusion, these data demonstrate that the IGF system has an important role in autocrine/paracrine growth of BON cells. The more potent antitumor activity of IFN-β compared with IFN-α could be explained by several effects on this system: 1) both IFNs inhibit the transcription of IGF-II, but the suppression is significantly higher after IFN-β than IFN-α and 2) only IFN-β inhibits the expression of IGF-I receptor.
Direct Deposition of Bamboo‐Like Carbon Nanotubes on Copper Substrates by Sulfur‐Assisted HFCVD
Authors: Katar Sri Lakshmi , González-Berríos Adolfo , De Jesus Joel , Weiner Brad , Morell Gerardo
Published: January 2009

Films of bamboo‐like carbon nanotubes (BCNTs) were grown directly on copper substrates by sulfur‐assisted hot filament chemical vapor deposition (HFCVD). The effects of substrate temperature and growth time over the BCNT structure were investigated. The films were characterized by scanning electron microscopy (SEM), Raman spectroscopy (RS), transmission electron microscopy (TEM), X‐ray photoelectron spectroscopy (XPS), and electron field emission (EFE) studies. SEM and Raman characterization indicate a transition from the growth of microcrystalline diamond to the growth of a dense entangled network of carbon nanotubes or fibers as the substrate temperature is increased from 400 to 900∘C that is accounted for by the base growth model. TEM images show that the nanotubes have regular arrays of nanocavities. These BCNTs show good electron field emission properties as other carbon films.
Turbulence Modeling of Torsional Couette Flows
Authors: Haddadi Sofia , Poncet Sébastien
Published: January 2009

The present study considers the numerical modeling of the turbulent flow inside a rotor‐stator
cavity subjected or not to a superimposed throughflow. Extensive numerical predictions based
on one‐point statistical modeling using a low Reynolds number second‐order full stress transport
closure (RSM model) are performed mainly in the case of turbulent flows with merged boundary
layers known as turbulent torsional Couette flows and belonging to regime III of Daily and Nece (1960). The RSM model has already shown its capability of predicting accurately the mean and turbulent
fields in various rotating disk configurations (Poncet, 2005; Poncet et al., 2005, 2007, 2008). For the first time, a detailed mapping of the
hydrodynamic flow over a wide range of rotational Reynolds numbers (180 000 ≤ Re ≤ 10 000 000), aspect ratios of the cavity (0.02 ≤ G ≤ 0.05), and flow rate coefficients (−10000 ≤ Cw ≤ 10000) is here provided in the turbulent torsional Couette flow regime.
Turbo Decoder for Low-Power Ultrawideband Communication Systems
Authors: Obiedat Esam A. , Cao Lei
Published: January 2009

A new method to reduce the computational complexity of the turbo decoding in ultrawideband (UWB) orthogonal frequency division multiplexing (OFDM) system is proposed. Existing stopping techniques for turbo decoding process using constrained decoding assume fixed signal-to-noise ratio (SNR) for all the OFDM symbol bits so they fail to yield an acceptable bit-error rate (BER) performance in multicarrier systems. In this paper, we propose a bit-level stopping technique for turbo decoding process based on the constrained decoding method. In this technique, we combine the cyclic redundancy check (CRC) with an adaptive threshold on the log likelihood ratio (LLR) on each subcarrier to detect for convergence. The threshold is adaptive in the sense that the threshold on the LLR of a bit is determined by the average SNR of the OFDM symbol and the channel gain of the transmission subcarrier. Results show that when the channel state information (CSI) is used to determine the threshold on LLR, the stopping technique can reduce the computational complexity by about 0.5–2.5 equivalent iterations compared to GENIE turbo without degradation in the BER performance.
Long-Term Antihypertensive Efficacy and Safety of the Oral Direct Renin Inhibitor Aliskiren
Authors: Schmieder Roland E. , Philipp Thomas , Guerediaga Javier , Gorostidi Manuel , Smith Beverly , Weissbach Nicole , Maboudian Mojdeh , Botha Jaco , van Ingen Hein
Published: January 2009

Background—

Diuretics are recommended as first-line agents for the treatment of hypertension. This randomized, double-blind, multicenter study assessed the long-term efficacy and safety of the direct renin inhibitor aliskiren in comparison with the diuretic hydrochlorothiazide in patients with essential hypertension.

Methods and Results—

After a 2- to 4-week placebo run-in, 1124 patients (mean sitting diastolic blood pressure [BP] 95 to 109 mm Hg) were randomized to aliskiren 150 mg (n=459), hydrochlorothiazide 12.5 mg (n=444), or placebo (n=221) once daily. Forced titration (to aliskiren 300 mg or hydrochlorothiazide 25 mg) occurred at week 3; at week 6, patients receiving placebo were reassigned (1:1 ratio) to aliskiren 300 mg or hydrochlorothiazide 25 mg. From week 12, amlodipine 5 mg was added and titrated to 10 mg from week 18 for patients whose BP remained uncontrolled. Efficacy variables were analyzed for the intent-to-treat population with the use of the last observation carried forward method. BP reductions (mean sitting systolic BP/mean sitting diastolic BP) were significantly greater with aliskiren- versus hydrochlorothiazide-based treatment at week 26 (−20.3/−14.2 versus −18.6/−13.0 mm Hg;
P
<0.05) and were also greater at week 52 (−22.1/−16.0 versus −21.2/−15.0 mm Hg;
P
<0.05 for mean sitting diastolic BP). At the end of the monotherapy period (week 12), aliskiren 300 mg was superior to hydrochlorothiazide 25 mg in reducing BP (−17.4/−12.2 versus −14.7/−10.3 mm H;
P
<0.001). Adverse event rates were similar with aliskiren- (65.2%) and hydrochlorothiazide-based therapy (61.5%). Hypokalemia was more frequent with hydrochlorothiazide-based therapy than aliskiren-based therapy (17.9% versus 0.9%;
P
<0.0001).

Conclusions—

Aliskiren treatment, both as monotherapy and with optional addition of amlodipine, provided significantly greater BP reductions than the respective hydrochlorothiazide regimens. Aliskiren-based therapy was well tolerated. Direct renin inhibition with aliskiren therefore represents an effective option for the long-term treatment of essential hypertension.