bluuebunny/crossref_metadata_2025 huggingface dataset:
REGULARITY AND GENERALIZED POLYNOMIAL CHAOS APPROXIMATION OF PARAMETRIC AND RANDOM SECOND-ORDER HYPERBOLIC PARTIAL DIFFERENTIAL EQUATIONS
Authors: HOANG VIET HA , SCHWAB CHRISTOPH
Published: July 2012

Initial boundary value problems of linear second-order hyperbolic partial differential equations whose coefficients depend on countably many random parameters are reduced to a parametric family of deterministic initial boundary value problems on an infinite dimensional parameter space. This parametric family is approximated by Galerkin projection onto finitely supported polynomial systems in the parameter space. We establish uniform stability with respect to the support of the resulting coupled hyperbolic systems, and provide sufficient smoothness and compatibility conditions on the data for the solution to exhibit analytic, respectively, Gevrey regularity with respect to the countably many parameters. Sufficient conditions for the p-summability of the generalized polynomial chaos expansion of the parametric solution in terms of the countably many input parameters are obtained and rates of convergence of best N-term polynomial chaos type approximations of the parametric solution are given. In addition, regularity both in space and time for the parametric family of solutions is proved for data satisfying certain compatibility conditions. The results allow obtaining convergence rates and stability of sparse space-time tensor product Galerkin discretizations in the parameter space.
FLOW-BASED REPUTATION: MORE THAN JUST RANKING
Authors: SIMONE ANTONINO , ŠKORIĆ BORIS , ZANNONE NICOLA
Published: July 2012

The last years have seen a growing interest in collaborative systems like electronic marketplaces and P2P file sharing systems where people are intended to interact with other people. Those systems, however, are subject to security and operational risks because of their open and distributed nature. Reputation systems provide a mechanism to reduce such risks by building trust relationships among entities and identifying malicious entities. A popular reputation model is the so-called flow-based model. Most existing reputation systems based on such a model provide only a ranking, without absolute reputation values; this makes it difficult to determine whether entities are actually trustworthy or untrustworthy. In addition, those systems ignore a significant part of the available information; as a consequence, reputation values may not be accurate. In this paper, we present a flow-based reputation metric that gives absolute values instead of merely a ranking. Our metric makes use of all the available information. We study, both analytically and numerically, the properties of the proposed metric and the effect of attacks on reputation values.
Information Architectures for Information Sharing Management — A Literature Review
Authors: Xie Shuyan , Helfert Markus , Ostrowski Lukasz
Published: July 2012

The struggle for commercial supremacy through information is being fought on two points: Information management and enabling technologies. Over the last years, there has been an increasing focus on information architecture (IA) to help organisations distinguish and manage information as corporate resource. As the information complexity increases, more IA studies show that IA could provide the structural and process design to facilitate enterprise interoperation under the information sharing environment. However, limited IA has been addressed for the usage of managing the information sharing. Motivated by this observation, this paper presents a literature review that IA can be used to understand and manage information sharing, utilising the enterprise information resource statically and dynamically through IA implementation. First, enterprise IA description and definition are presented. Second, we analyse IA from a static and dynamic view to reveal the research streams on an architectural approach for information sharing management. Third, contributions and limitations are discussed. It is finally concluded by providing future IA research directions and implications for empirical applications. Our research illustrates that IA deployment imposes a positive influence on information sharing management.
Knowledge Sharing and its Impact on Knowledge Creation
Authors: Akhavan Peyman , Ghojavand Somayeh , Abdali Roghayeh
Published: July 2012

It is known that "knowledge management" is associated with significant benefits which can empower organisations to get more competitive advantages in their market. Knowledge sharing and knowledge creation are the two vital aspects of knowledge management which play an important role in creating organisational value. The value-creation of knowledge depends on level of sharing knowledge and skills among people across the organisation. So, most companies are focussed on enhancing their capability of knowledge sharing to create new knowledge. The aim of this paper is to test empirically the degree of influence of different knowledge-sharing mechanisms on the knowledge creation capability of Iranian manufacturing industries.

A question survey was administered to a sample of manufacturing industries operating in Iran to elicit opinions of the personnel on the relationship between knowledge sharing and knowledge creation. The questions were structured mostly based on Sa'enz et al. (2009) and Choi and Lee (2002) studies. More than 400 respondents from 16 organisations responded to the survey. A short training course was held in all sample firms separately to explain importance and applications of knowledge management for respondents. SPSS and LISREL software were utilised to analyse research data using Regression tests and structural equation modelling (SEM). Results obtained show that knowledge sharing has a positive influence on the knowledge creation in Iranian manufacturing industries. However, a meaningful relationship was observed between information technology and management processes and two constructs of knowledge creation. The main contribution of the paper is to provide empirical evidence about the impact of knowledge sharing on knowledge creation. Moreover, it reveals what the most effective knowledge-sharing mechanisms are for this purpose, and provides companies with some implications in order to shape their knowledge management strategies.
AN IMPLICIT DIFFERENCE SCHEME FOCUSING ON THE LOCAL CONSERVATION PROPERTIES FOR BURGERS EQUATION
Authors: HU WEIPENG , DENG ZICHEN , HAN SONGMEI
Published: July 2012

Focusing on the local conservation properties, a nine-point implicit difference scheme derived from the multi-symplectic idea, which is named as a generalized multi-symplectic integrator, is presented for the Burgers equation firstly. And then, the associated proofs needed on the local conservation properties of the scheme are given in detail. Finally, to illustrate the high accuracy, the good local conservation properties as well as the excellent long-time numerical behavior of the scheme, the numerical experiments on the single-front solution of the Burgers equation by the implicit scheme are reported.
A COMPARISON BETWEEN THE NMM AND THE XFEM IN DISCONTINUITY MODELING
Authors: AN XINMEI , FU GUOYANG , MA GUOWEI
Published: July 2012

Discontinuities such as voids, cracks, material interfaces, and joints widely exist in nature. Conventional finite element method (FEM) requires the finite element mesh to coincide with the discontinuities, which often complicates the meshing task. When evolution of discontinuities are necessary, remeshing is inevitable, which makes the simulation tedious and time-consuming. In order to overcome such inconveniences, the extended finite element method (XFEM) and the generalized finite element method (GFEM) were developed by incorporating special functions into the standard finite element approximation space based on partition of unity. The finite element mesh is allowed to be totally independent of the discontinuities and remeshing is totally avoided for discontinuity evolution. The numerical manifold method (NMM) can also be viewed as an extension or generalization to the conventional FEM. Different from the XFEM/GFEM, the approximation in the NMM is based on covers. The NMM models discontinuities by its dual cover system. In this paper, a detailed comparison between the NMM and the XFEM in discontinuity modeling is presented. Their advantages and disadvantages are pointed out. How the dual cover system in the NMM favors the complex crack modeling is emphasized. Potential extensions to the XFEM and the NMM are suggested.
LEAST-SQUARES MESHFREE COLLOCATION METHOD
Authors: JIANG BO-NAN
Published: July 2012

A least-squares meshfree collocation method is presented. The method is based on the first-order differential equations in order to result in a better conditioned linear algebraic equations, and to obtain the primary variables (displacements) and the dual variables (stresses) simultaneously with the same accuracy. The moving least-squares approximation is employed to construct the shape functions. The sum of squared residuals of both differential equations and boundary conditions at nodal points is minimized. The present method does not require any background mesh and additional evaluation points, and thus is a truly meshfree method. Unlike other collocation methods, the present method does not involve derivative boundary conditions, therefore no stabilization terms are needed, and the resulting stiffness matrix is symmetric positive definite. Numerical examples show that the proposed method possesses an optimal rate of convergence for both primary and dual variables, if the nodes are uniformly distributed. However, the present method is sensitive to the choice of the influence length. Numerical examples include one-dimensional diffusion and convection-diffusion problems, two-dimensional Poisson equation and linear elasticity problems.
Spectral study on one-electron-oxidized di(phthalocyaninato)rare-earths(III)
Authors: Isago Hiroaki
Published: July 2012

Nine double-decker bis(phthalocyaninato)rare-earth(III) complexes, [M(pc)2] (green radical species; M = Sc, Y, La, Pr, Sm, Eu, Tb, Ho, Yb ) have been electrochemically and spectro-electrochemically investigated in CH2Cl2 . All of them show one oxidation and three reduction waves, which involve phthalocyanine macrocycles. Apart from the lanthanum derivative, the first oxidation and reduction potentials show linear cathodic shift with an increase in ionic radius of the central metal (ri), whereas the second and third reduction little depend on ri. Electrochemical oxidation (around the oxidation potential) and chemical oxidation produced the same red~orange species (depending on the central metal). Their optical absorption spectra show three characteristic bands in 400~600, 600~750, and 800~1200 nm in visible and near-infrared region and their peak positions (in cm-1) linearly depend on ri (except for La). Assignment of these bands has been done based on magnetic circular dichroism spectroscopy and the electrochemical data.
SPECTRAL PROPERTIES OF RANDOM TRIANGULAR MATRICES
Authors: BASU RIDDHIPRATIM , BOSE ARUP , GANGULY SHIRSHENDU , HAZRA RAJAT SUBHRA
Published: July 2012

We prove the existence of the limiting spectral distribution (LSD) of symmetric triangular patterned matrices and also establish the joint convergence of sequences of such matrices. For the particular case of the symmetric triangular Wigner matrix, we derive expression for the moments of the LSD using properties of Catalan words. The problem of deriving explicit formulae for the moments of the LSD does not seem to be easy to solve for other patterned matrices. The LSD of the non-symmetric triangular Wigner matrix also does not seem to be easy to establish.
EMPIRICAL DISTRIBUTIONS OF LAPLACIAN MATRICES OF LARGE DILUTE RANDOM GRAPHS
Authors: JIANG TIEFENG
Published: July 2012

We study the spectral properties of the Laplacian matrices and the normalized Laplacian matrices of the Erdös–Rényi random graph G(n, pn) for large n. Although the graph is simple, we discover some interesting behaviors of the two Laplacian matrices. In fact, under the dilute case, that is, pn∈ (0, 1) and npn→ ∞, we prove that the empirical distribution of the eigenvalues of the Laplacian matrix converges to a deterministic distribution, which is the free convolution of the semi-circle law and N(0, 1). However, for its normalized version, we prove that the empirical distribution converges to the semi-circle law.
A Computational Framework for Media Bias Mitigation
Authors: Park Souneil , Kang Seungwoo , Chung Sangyoung , Song Junehwa
Published: July 2012

Bias in the news media is an inherent flaw of the news production process. The bias often causes a sharp increase in political polarization and in the cost of conflict on social issues such as the Iraq war. This article presents NewsCube, a novel Internet news service which aims to mitigate the effect of media bias. NewsCube automatically creates and promptly provides readers with multiple classified views on a news event. As such, it helps readers understand the event from a plurality of views and to formulate their own, more balanced, viewpoints. The media bias problem has been studied extensively in mass communications and social science. This article reviews related mass communication and journalism studies and provides a structured view of the media bias problem and its solution. We propose media bias mitigation as a practical solution and demonstrate it through NewsCube. We evaluate and discuss the effectiveness of NewsCube through various performance studies.
Investigating the Persuasion Potential of Recommender Systems from a Quality Perspective
Authors: Cremonesi Paolo , Garzotto Franca , Turrin Roberto
Published: July 2012

Recommender Systems (RSs) help users search large amounts of digital contents and services by allowing them to identify the items that are likely to be more attractive or useful. RSs play an important persuasion role, as they can potentially augment the users’ trust towards in an application and orient their decisions or actions towards specific directions. This article explores the persuasiveness of RSs, presenting two vast empirical studies that address a number of research questions.

First, we investigate if a design property of RSs, defined by the statistically measured quality of algorithms, is a reliable predictor of their potential for persuasion. This factor is measured in terms of perceived quality, defined by the overall satisfaction, as well as by how users judge the accuracy and novelty of recommendations. For our purposes, we designed an empirical study involving 210 subjects and implemented seven full-sized versions of a commercial RS, each one using the same interface and dataset (a subset of Netflix), but each with a different recommender algorithm. In each experimental configuration we computed the statistical quality (recall and F-measures) and collected data regarding the quality perceived by 30 users. The results show us that algorithmic attributes are less crucial than we might expect in determining the user’s perception of an RS’s quality, and suggest that the user’s judgment and attitude towards a recommender are likely to be more affected by factors related to the user experience.

Second, we explore the persuasiveness of RSs in the context of large interactive TV services. We report a study aimed at assessing whether measurable persuasion effects (e.g., changes of shopping behavior) can be achieved through the introduction of a recommender. Our data, collected for more than one year, allow us to conclude that, (1) the adoption of an RS can affect both the lift factor and the conversion rate, determining an increased volume of sales and influencing the user’s decision to actually buy one of the recommended products, (2) the introduction of an RS tends to diversify purchases and orient users towards less obvious choices (the long tail), and (3) the perceived novelty of recommendations is likely to be more influential than their perceived accuracy.

Overall, the results of these studies improve our understanding of the persuasion phenomena induced by RSs, and have implications that can be of interest to academic scholars, designers, and adopters of this class of systems.
A framework for the checking and refactoring of crosscutting concepts
Authors: Shonle Macneil , Griswold William G. , Lerner Sorin
Published: July 2012

Programmers employ crosscutting concepts, such as design patterns and other programming idioms, when their design ideas cannot be efficiently or effectively modularized in the underlying programming language. As a result, implementations of these crosscutting concepts can be hard to change even when the code is well structured.

In this article, we describe Arcum, a system that supports the modular maintenance of crosscutting concepts. Arcum can be used to both check essential constraints of crosscutting concepts and to substitute crosscutting concept implementations with alternative implementations. Arcum is complementary to existing refactoring systems that focus on meaning-preserving program transformations at the programming-language-semantics level, because Arcum focuses on transformations at the conceptual level.

We present the underpinnings of the Arcum approach and show how Arcum can be used to address several classical software engineering problems.
DARWIN
Authors: Qi Dawei , Roychoudhury Abhik , Liang Zhenkai , Vaswani Kapil
Published: July 2012

Bugs in programs are often introduced when programs evolve from a stable version to a new version. In this article, we propose a new approach called
DARWIN
for automatically finding potential root causes of such bugs. Given two programs—a reference program and a modified program—and an input that fails on the modified program, our approach uses symbolic execution to automatically synthesize a new input that (a) is very similar to the failing input and (b) does not fail. We find the potential cause(s) of failure by comparing control-flow behavior of the passing and failing inputs and identifying code fragments where the control flows diverge.

A notable feature of our approach is that it handles hard-to-explain bugs, like code missing errors, by pointing to code in the reference program. We have implemented this approach and conducted experiments using several real-world applications, such as the Apache Web server, libPNG (a library for manipulating PNG images), and TCPflow (a program for displaying data sent through TCP connections). In each of these applications,
DARWIN
was able to localize bugs with high accuracy. Even though these applications contain several thousands of lines of code,
DARWIN
could usually narrow down the potential root cause(s) to less than ten lines. In addition, we find that the inputs synthesized by
DARWIN
provide additional value by revealing other undiscovered errors.
Demo hour
Authors: Chuang Yaliang , Chiu Ling-Yuah , Hu Jya-Cheng , Chang George , Kao Hsin-Liu , Lin Tsen-Ying , Huang Kuang-Shih , Chang Li-Erh , Liang Rung-Huei , Kan Tai-Wei , Yang Li-Te , Tsai Shuang-Yu
Published: July 2012

Demo Hour highlights new prototypes and projects that exemplify innovation and novel forms of interaction.

Leah Maestri, Editor
Considering the rights (and wrongs) of community technology
Authors: Le Dantec Christopher A.
Published: July 2012

Community + Culture features practitioner perspectives on designing technologies for and with communities. We highlight compelling projects and provocative points of view that speak to both community technology practice and the interaction design field as a whole.

Christopher A. Le Dantec
Sensible smartphones for Southern Africa
Authors: Jensen Kasper Løvborg
Published: July 2012

This forum looks at how the fields of interaction design and HCI can extend to cover "developing" communities around the world, ones that are gaining access to digital technology for the first time.

Gary Marsden, Editor
A personal history of modeless text editing and cut/copy-paste
Authors: Tesler Larry
Published: July 2012

Timelines provides perspectives on HCI history, glancing back at a road that sometimes took unexpected branches and turns. History is not a dry list of events; it is about points of view and differing interpretations.

Jonathan Grudin, Editor
Partially Evaluating Finite-State Runtime Monitors Ahead of Time
Authors: Bodden Eric , Lam Patrick , Hendren Laurie
Published: July 2012

Finite-state properties account for an important class of program properties, typically related to the order of operations invoked on objects. Many library implementations therefore include manually written finite-state monitors to detect violations of finite-state properties at runtime. Researchers have recently proposed the explicit specification of finite-state properties and automatic generation of monitors from the specification. However, runtime monitoring only shows the presence of violations, and typically cannot prove their absence. Moreover, inserting a runtime monitor into a program under test can slow down the program by several orders of magnitude.

In this work, we therefore present a set of four static whole-program analyses that partially evaluate runtime monitors at compile time, with increasing cost and precision. As we show, ahead-of-time evaluation can often evaluate the monitor completely statically. This may prove that the program cannot violate the property on any execution or may prove that violations do exist. In the remaining cases, the partial evaluation converts the runtime monitor into a residual monitor. This monitor only receives events from program locations that the analyses failed to prove irrelevant. This makes the residual monitor much more efficient than a full monitor, while still capturing all property violations at runtime.

We implemented the analyses in Clara, a novel framework for the partial evaluation of AspectJ-based runtime monitors, and validated our approach by applying Clara to finite-state properties over several large-scale Java programs. Clara proved that most of the programs never violate our example properties. Some programs required monitoring, but in those cases Clara could often reduce the monitoring overhead to below 10%. We observed that several programs did violate the stated properties.
Structured Communication-Centered Programming for Web Services
Authors: Carbone Marco , Honda Kohei , Yoshida Nobuko
Published: July 2012

This article relates two different paradigms of descriptions of communication behavior, one focusing on global message flows and another on end-point behaviors, using formal calculi based on session types. The global calculus, which originates from a Web service description language (W3C WS-CDL), describes an interaction scenario from a vantage viewpoint; the end-point calculus, an applied typed
π
-calculus, precisely identifies a local behavior of each participant. We explore a theory of end-point projection, by which we can map a global description to its end-point counterparts preserving types and dynamics. Three principles of well-structured description and the type structures play a fundamental role in the theory.
On a Technique for Transparently Empowering Classical Compiler Optimizations on Multithreaded Code
Authors: Joisha Pramod G. , Schreiber Robert S. , Banerjee Prithviraj , Boehm Hans-J. , Chakrabarti Dhruva R.
Published: July 2012

A large body of data-flow analyses exists for analyzing and optimizing sequential code. Unfortunately, much of it cannot be directly applied on parallel code, for reasons of correctness. This article presents a technique to automatically, aggressively, yet safely apply sequentially-sound data-flow transformations,
without change
, on shared-memory programs. The technique is founded on the notion of program references being “siloed” on certain control-flow paths. Intuitively, siloed references are free of interference from other threads within the confines of such paths. Data-flow transformations can, in general, be unblocked on siloed references.

The solution has been implemented in a widely used compiler. Results on benchmarks from SPLASH-2 show that performance improvements of up to 41% are possible, with an average improvement of 6% across all the tested programs over all thread counts.
Netshare and stochastic netshare
Authors: Lam Vinh The , Radhakrishnan Sivasankar , Pan Rong , Vahdat Amin , Varghese George
Published: July 2012

Application performance in cloud data centers often depends crucially on network bandwidth, not just the aggregate data transmitted as in typical SLAs. We describe a mechanism for data center networks called
NetShare
that requires no hardware changes to routers but allows bandwidth to be allocated predictably across services based on weights. The weights are either specified by a manager, or automatically assigned at each switch port based on a virtual machine heuristic for isolation. Bandwidth unused by a service is shared proportionately by other services, providing weighted hierarchical max-min fair sharing. On a testbed of Fulcrum switches, we demonstrate that NetShare provides bandwidth isolation in various settings, including multipath networks.
The collateral damage of internet censorship by DNS injection
Authors: Anonymous
Published: July 2012

Some ISPs and governments (most notably the Great Firewall of China) use DNS injection to block access to "unwanted" websites. The censorship tools inspect DNS queries near the ISP's boundary routers for sensitive domain keywords and inject forged DNS responses, blocking the users from accessing censored sites, such as twitter and facebook. Unfortunately this causes collateral damage, affecting communication beyond the censored networks when outside DNS traffic traverses censored links. In this paper, we analyze the causes of the collateral damages and measure the Internet to identify the injecting activities and their effect. We find 39 ASes in China injecting forged DNS replies. Furthermore, 26 of 43,000 measured open resolvers outside China, distributed in 109 countries, may suffer some collateral damage from these forged replies. Different from previous work that considers the collateral damage being limited to queries to root servers (F, I, J) located in China, we find that most collateral damage arises when the paths between resolvers and some TLD name servers transit through ISPs in China.
Differential piracy
Authors: Crowcroft Jon
Published: July 2012

In all seriousness, Differential
Privacy
is a new technique and set of tools for managing responses to statistical queries over secured data, in such a way that the user cannot reconstruct more precise identification of principles in the dataset beyond a formally well-specified bound. This means that personally sensitive data such as Internet packet traces or social network measurements can be shared between researchers without invading personal privacy, and that assurances can be made with accuracy.

With less seriousness, I would like to talk about Differential
Piracy
, but not without purpose. For sure, while there are legitimate reasons for upstanding citizens to live without fear of eternal surveillance, there is also a segment of society that gets away with things they shouldn't, under a cloak. Perhaps that is the (modest) price we have to pay for a modicum less paranoia in this brave new world.

So, there has been a lot of work recently on Piracy Preserving Queries and Differential Piracy. These two related technologies exploit new ideas in statistical security. Rather than security through obscurity, the idea is to offer privacy through lack of differentiation (no, not inability to perform basic calculus, more the inability to distinguish between large numbers of very similar things).
The 4th workshop on active internet measurements (AIMS-4) report
Authors: claffy kc
Published: July 2012

On February 8-10, 2012, CAIDA hosted the fourth Workshop on Active Internet Measurements (AIMS-4) as part of our series of Internet Statistics and Metrics Analysis (ISMA) workshops. As with the previous three AIMS workshops, the goals were to further our understanding of the potential and limitations of active measurement research and infrastructure in the wide-area Internet, and to promote cooperative solutions and coordinated strategies to address future data needs of the network and security operations and research communities. This year we continued to focus on how measurement can illuminate two specific public policy concerns: IPv6 deployment and broadband performance. This report briefly describes topics discussed at this year's workshop. Slides and other materials related to the workshop are available at http://www.caida.org/.
Turing, the internet and a theory for architecture
Authors: Trossen Dirk
Published: July 2012

The late noughties have seen an influx of work in different scientific disciplines, all addressing the question of 'design' and 'architecture'. It is a battle between those advocating the theory of 'emergent properties' and others who strive for a 'theory for 'architecture'. We provide a particular insight into this battle, represented in the form of a story that focuses on the role of a possibly unusual protagonist and his influence on computer science, the Internet, architecture and beyond. We show his relation to one of the great achievements of system engineering, the Internet, and the possible future as it might unfold.

Note from the writer: The tale is placed in a mixture of reality and fiction, while postulating a certain likelihood for this fiction. There is no proof for the assertions made in this tale, leaving the space for a sequel to be told.
Refactoring network infrastructure to improve manageability
Authors: Chetty Marshini , Feamster Nick
Published: July 2012

Managing a home network is challenging because the underlying infrastructure is so complex. Existing interfaces either hide or expose the network's underlying complexity, but in both cases, the information that is shown does not necessarily allow a user to complete desired tasks. Recent advances in software defined networking, however, permit a redesign of the underlying network and protocols, potentially allowing designers to move complexity further from the user and, in some cases, eliminating it entirely. In this paper, we explore whether the choices of what to make visible to the user in the design of today's home network infrastructure, performance, and policies make sense. We also examine whether new capabilities for refactoring the network infrastructure - changing the underlying system without compromising existing functionality - should cause us to revisit some of these choices. Our work represents a case study of how co-designing an interface and its underlying infrastructure could ultimately improve interfaces for that infrastructure.
Adaptive forwarding in named data networking
Authors: Yi Cheng , Afanasyev Alexander , Wang Lan , Zhang Beichuan , Zhang Lixia
Published: July 2012

In Named Data Networking (NDN) architecture, packets carry data names rather than source or destination addresses. This change of paradigm leads to a new data plane: data consumers send out Interest packets, routers forward them and maintain the state of pending Interests, which is used to guide Data packets back to the consumers. NDN routers' forwarding process is able to detect network problems by observing the two-way traffic of Interest and Data packets, and explore multiple alternative paths without loops. This is in sharp contrast to today's IP forwarding process which follows a single path chosen by the routing process, with no adaptability of its own. In this paper we outline the design of NDN's adaptive forwarding, articulate its potential benefits, and identify open research issues.
An automatic control interface for network-accessible embedded instruments
Authors: Smecher Graeme , Aubin François , George Elizabeth , de Haan Tijmen , Kennedy James , Dobbs Matt
Published: July 2012

We describe a metaprogrammed control interface and support library for network-accessible embedded systems. Together, this project permits functions written in standard C code to be exposed via a network interface expressed in JSON. In turn, this JSON interface mates with a Python library that provides a high-level, user-friendly, and expressive development environment.

This control interface removes the need to explicitly code interactions at the Python and network layers. As a result, the volume of error-prone and redundant hand-written code (e.g. for error-checking and validation) is vastly reduced.
A hardware time manager implementation for the
Xenomai
real-time kernel of embedded Linux
Authors: Olivier Pierre , Boukhobza Jalil
Published: July 2012

Nowadays, the use of embedded operating systems in different embedded projects is subject to a tremendous growth. Embedded Linux is becoming one of those most popular EOSs due to its modularity, efficiency, reliability, and cost. One way to make it hard real-time is to include a real-time kernel like Xenomai. One of the key characteristics of a Real-Time Operating System (RTOS) is its ability to meet execution time deadlines deterministically. So, the more precise and flexible the time management can be, the better it can handle efficiently the determinism for different embedded applications. RTOS time precision is characterized by a specific periodic interrupt service controlled by a software time manager. The smaller the period of the interrupt, the better the precision of the RTOS, the more it overloads the CPU, and though reduces the overall efficiency of the RTOS. In this paper, we propose to drastically reduce these overheads by migrating the time management service of Xenomai into a configurable hardware component to relieve the CPU. The hardware component is implemented in a Field Programmable Gate Array coupled to the CPU. This work was achieved in a Master degree project where students could apprehend many fields of embedded systems: RTOS programming, hardware design, performance evaluation, etc.
On benchmarking embedded Linux flash file systems
Authors: Olivier Pierre , Boukhobza Jalil , Senn Eric
Published: July 2012

Due to its attractive characteristics in terms of performance, weight and power consumption, NAND flash memory became the main non volatile memory (NVM) in embedded systems. Those NVMs also present some specific characteristics/constraints: good but asymmetric I/O performance, limited lifetime, write/erase granularity asymmetry, etc.

Those peculiarities are either managed in hardware for flash disks (SSDs, SD cards, USB sticks, etc.) or in software for raw embedded flash chips. When managed in software, flash algorithms and structures are implemented in a specific flash file system (FFS). In this paper, we present a performance study of the most widely used FFSs in embedded Linux: JFFS2, UBIFS, and YAFFS. We show some very particular behaviors and large performance disparities for tested FFS operations such as mounting, copying, and searching file trees, compression, etc.
High-performance computing in mobile services
Authors: Liu Zhen
Published: July 2012

With the ever increasing popularity of smart phones, mobile services have been evolving rapidly to allow users to enjoy localized and personalized experiences. Users can discover local information and keep connected with family and friends on the go, and ultimately to experience the convergence of cyber space and physical world where digital technologies are interwoven into the day-to-day life. A pivotal component of such a cyber-physical convergence is the contextual intelligence. The extraction and dissemination of contextual information around users is the key for the cyber capabilities to be applied to physical activities and for the cyber world to better reflect the physical reality. In this talk, we shall address some issues arising from context-based mobile services. In particular, we discuss how mobility impacts contextual relevancy and personalization in mobile services. The relevancy and timeliness of contextual information not only are essential for these services to deliver great user experiences, but also put significant computation pressure on service infrastructure that processes continuous data streams in real time and disseminate relevant data to a large amount of mobile users. This talk will explore the challenges and opportunities for high-performance computing in mobile services. Based on key findings from large-scale mobile measurement data, the talk will analyze the tradeoff of different computing architectures, present case studies of scalable system design and implementation for personalized mobile services, and conclude with open challenges for the broad research community in performance measurement and modeling.
Energy-efficient congestion control
Authors: Gan Lingwen , Walid Anwar , Low Steven
Published: July 2012

Various link bandwidth adjustment mechanisms are being developed to save network energy. However, their interaction with congestion control can significantly reduce network throughput, and is not well understood. We firstly put forward a framework to study this interaction, and then propose an easily implementable dynamic bandwidth adjustment (DBA) mechanism for the links. In DBA, each link updates its bandwidth according to an integral control law to match its average buffer size with a target buffer size. We prove that DBA reduces link bandwidth without sacrificing throughput---DBA only turns off excess bandwidth---in the presence of congestion control. Preliminary ns2 simulations confirm this result.
How well can congestion pricing neutralize denial of service attacks?
Authors: Vulimiri Ashish , Agha Gul A. , Godfrey Philip Brighten , Lakshminarayanan Karthik
Published: July 2012

Denial of service protection mechanisms usually require classifying malicious traffic, which can be difficult. Another approach is to price scarce resources. However, while congestion pricing has been suggested as a way to combat DoS attacks, it has not been shown quantitatively how much damage a malicious player could cause to the utility of benign participants. In this paper, we quantify the protection that congestion pricing affords against DoS attacks, even for powerful attackers that can control their packets' routes. Specifically, we model the limits on the resources available to the attackers in three different ways and, in each case, quantify the maximum amount of damage they can cause as a function of their resource bounds. In addition, we show that congestion pricing is provably superior to fair queueing in attack resilience.
Temperature management in data centers
Authors: El-Sayed Nosayba , Stefanovici Ioan A. , Amvrosiadis George , Hwang Andy A. , Schroeder Bianca
Published: July 2012

The energy consumed by data centers is starting to make up a significant fraction of the world's energy consumption and carbon emissions. A large fraction of the consumed energy is spent on data center cooling, which has motivated a large body of work on temperature management in data centers. Interestingly, a key aspect of temperature management has not been well understood: controlling the setpoint temperature at which to run a data center's cooling system. Most data centers set their thermostat based on (conservative) suggestions by manufacturers, as there is limited understanding of how higher temperatures will affect the system. At the same time, studies suggest that increasing the temperature setpoint by just one degree could save 2-5% of the energy consumption. This paper provides a multi-faceted study of temperature management in data centers. We use a large collection of field data from different production environments to study the impact of temperature on hardware reliability, including the reliability of the storage subsystem, the memory subsystem and server reliability as a whole. We also use an experimental testbed based on a thermal chamber and a large array of benchmarks to study two other potential issues with higher data center temperatures: the effect on server performance and power. Based on our findings, we make recommendations for temperature management in data centers, that create the potential for saving energy, while limiting negative effects on system reliability and performance.
Energy storage in datacenters
Authors: Wang Di , Ren Chuangang , Sivasubramaniam Anand , Urgaonkar Bhuvan , Fathy Hosam
Published: July 2012

Energy storage - in the form of UPS units - in a datacenter has been primarily used to fail-over to diesel generators upon power outages. There has been recent interest in using these Energy Storage Devices (ESDs) for demand-response (DR) to either shift peak demand away from high tariff periods, or to shave demand allowing aggressive under-provisioning of the power infrastructure. All such prior work has only considered a single/specific type of ESD (typically re-chargeable lead-acid batteries), and has only employed them at a single level of the power delivery network. Continuing technological advances have provided us a plethora of competitive ESD options ranging from ultra-capacitors, to different kinds of batteries, flywheels and even compressed air-based storage. These ESDs offer very different trade-offs between their power and energy costs, densities, lifetimes, and energy efficiency, among other factors, suggesting that employing hybrid combinations of these may allow more effective DR than with a single technology. Furthermore, ESDs can be placed at different, and possibly multiple, levels of the power delivery hierarchy with different associated trade-offs. To our knowledge, no prior work has studied the extensive design space involving multiple ESD technology provisioning and placement options. This paper intends to fill this critical void, by presenting a theoretical framework for capturing important characteristics of different ESD technologies, the trade-offs of placing them at different levels of the power hierarchy, and quantifying the resulting cost-benefit trade-offs as a function of workload properties.
Learning the graph of epidemic cascades
Authors: Netrapalli Praneeth , Sanghavi Sujay
Published: July 2012

We consider the problem of finding the graph on which an epidemic spreads, given
only
the times when each node gets infected. While this is a problem of central importance in several contexts -- offline and online social networks, e-commerce, epidemiology -- there has been very little work, analytical or empirical, on finding the graph. Clearly, it is impossible to do so from just one epidemic; our interest is in learning the graph from a small number of independent epidemics.

For the classic and popular "independent cascade" epidemics, we analytically establish sufficient conditions on the number of epidemics for both the global maximum-likelihood (ML) estimator, and a natural greedy algorithm to succeed with high probability. Both results are based on a key observation: the global graph learning problem decouples into n local problems -- one for each node. For a node of degree d, we show that its neighborhood can be reliably found once it has been infected O(d
2
log n) times (for ML on general graphs) or O(d log n) times (for greedy on trees). We also provide a corresponding information-theoretic lower bound of Ω(d log n); thus our bounds are essentially tight.

Furthermore, if we are given side-information in the form of a super-graph of the actual graph (as is often the case), then the number of epidemic samples required -- in all cases -- becomes independent of the network size n.
What is a good buffer cache replacement scheme for mobile flash storage?
Authors: Kim Hyojun , Ryu Moonkyung , Ramachandran Umakishore
Published: July 2012

Smartphones are becoming ubiquitous and powerful. The Achilles' heel in such devices that limits performance is the storage. Low-end flash memory is the storage technology of choice in such devices due to energy, size, and cost considerations. In this paper, we take a critical look at the performance of flash on smartphones for mobile applications. Specifically, we ask the question whether the state-of-the-art buffer cache replacement schemes proposed thus far (both flash-agnostic and flash-aware ones) are the right ones for mobile flash storage. To answer this question, we first expose the limitations of current buffer cache performance evaluation methods, and propose a novel evaluation framework that is a hybrid between trace-driven simulation and real implementation of such schemes inside an operating system. Such an evaluation reveals some unexpected and surprising insights on the performance of buffer management schemes that contradicts conventional wisdom. Armed with this knowledge, we propose a new buffer cache replacement scheme called SpatialClock.

Using our evaluation framework, we show the superior performance of SpatialClock relative to the state-of-the-art for mobile flash storage.
Versatile refresh
Authors: Alizadeh Mohammad , Javanmard Adel , Chuang Shang-Tse , Iyer Sundar , Lu Yi
Published: July 2012

Multi-banked embedded DRAM (eDRAM) has become increasingly popular in high-performance systems. However, the data retention problem of eDRAM is exacerbated by the larger number of banks and the high-performance environment in which it is deployed: The data retention time of each memory cell decreases while the number of cells to be refreshed increases. For this, multi-bank designs offer a concurrent refresh mode, where idle banks can be refreshed concurrently during read and write operations. However, conventional techniques such as periodically scheduling refreshes---with priority given to refreshes in case of conflicts with reads or writes---have variable performance, increase read latency, and can perform poorly in worst case memory access patterns. We propose a novel refresh scheduling algorithm that is low-complexity, produces near-optimal throughput with universal guarantees, and is tolerant to bursty memory access patterns. The central idea is to decouple the scheduler into two simple-to-implement modules: one determines which cell to refresh next and the other determines when to force an idle cycle in all banks. We derive necessary and sufficient conditions to guarantee data integrity for all access patterns, with any given number of banks, rows per bank, read/write ports and data retention time. Our analysis shows that there is a tradeoff between refresh overhead and burst tolerance and characterizes this tradeoff precisely. The algorithm is shown to be near-optimal and achieves, for instance, 76.6% reduction in worst-case refresh overhead from the periodic refresh algorithm for a 250MHz eDRAM with 10us retention time and 16 banks each with 128 rows. Simulations with Apex-Map synthetic benchmarks and switch lookup table traffic show that VR can almost completely hide the refresh overhead for memory accesses with moderate-to-high multiplexing across memory banks.
ADP
Authors: Yoo Wucherl , Larson Kevin , Baugh Lee , Kim Sangkyum , Campbell Roy H.
Published: July 2012

Performance characterization of applications' hardware behavior is essential for making the best use of available hardware resources. Modern architectures offer access to many hardware events that are capable of providing information to reveal architectural performance bottlenecks throughout the core and memory hierarchy. These events can provide programmers with unique and powerful insights into the causes of the resource bottlenecks in their applications. However, interpreting these events has been a significant challenge. We present an automated system that uses machine learning to identify an application's performance problems. Our system provides programmers with insights about the performance of their applications while shielding them from the onerous task of digesting hardware events. It uses a decision tree algorithm, random forests on our micro-benchmarks to fingerprint the performance problems. Our system divides a profiled application into functions and automatically classifies each function by the dominant hardware resource bottlenecks. Using the classifications from the hotspot functions, we were able to achieve an average speedup of 1.73 from three applications in the PARSEC benchmark suite. Our system provides programmers with a guideline of where, what, and how to fix the detected performance problems in applications, which would have otherwise required considerable architectural knowledge.