bluuebunny/crossref_metadata_2025 huggingface dataset:
Implications of Onicescu's informational energy in some fundamental physical models
Authors: Agop Maricel , Gavriluţ Alina , Rezuş Elena
Published: January 2015

Correlating Shannon's maximum informational entropy variational principle with the constant value of Onicescu's informational energy, the uncertainty relations for canonical systems with SL(2R) invariance are obtained.

The constant value of Onicescu's informational energy corresponds, through transitivity manifolds of the SL(2R) group, to the ergodic theorem and, in particular case of a linear oscillator, to a quantification condition. Specifying de Broglie's idea by a periodic field in a complex coordinate, it is proved that the oscillator synchronization group of the same ensemble is still an achievement of the SL(2R) (Barbilian's group). Integrally invoking the invariant functions through the simultaneous action of the two isomorphic SL(2R) groups, the uncertainty relations and Stoler group of synchronization among oscillators from different ensembles (i.e., the second quantification when the annihilation and creation operators refer to a linear oscillator) are obtained. Barbilian's group parameters are interpreted by means of a variational principle as field amplitudes of a stationary vacuum metric.
A variational calculation of magnetized correlated fermion system using a spin-dependent correlation: Application to liquid 3He
Authors: Bordbar Gholam Hossein , Sabet Mohammad Taghi Mohammadi
Published: January 2015

In the presence of magnetic field, we have employed a spin-dependent correlation function to investigate the properties of liquid 3 He using the variational method based on the cluster expansion of the energy. It has been indicated that at all relevant magnetic fields and densities, the inclusion of spin-dependency for the correlation function leads to the lower magnitudes for the kinetic, magnetic and potential energies, and therefore the total energy of this system. We have seen that the spin–spin correlation affects the system to be less magnetized compared to the case in which we consider the spin-independent correlation, especially at low densities. In the case of spin–spin correlation function, our results show a maximum in the magnetic susceptibility, and therefore a meta-magnetic instability for the system for the magnetic fields in the range 50 T ≤ B ≤ 60 T . This behavior has not been observed in the case of spin-independent correlation.
Codimension-Two Big-Bang Bifurcation in a ZAD-Controlled Boost DC-DC Converter
Authors: Amador A. , Casanova S. , Granada H. A. , Olivar G. , Hurtado J.
Published: January 2015

In this paper, we study some nonlinear behaviors in a two-dimensional system defined by a Boost Converter controlled by CPWM (Centered Pulse-Width Modulation) and a ZAD (Zero Average Dynamics) strategy. The dynamics was analyzed using a discrete-time map, which consists of a sampled system at each switching cycle. The structure of the two-parametric space is characterized analytically. This allows proving the existence and stability of an infinite number of codimension-one curves that intersect at the same point in the two-parametric space. This phenomenon has been called a big-bang bifurcation.
Memristor Based van der Pol Oscillation Circuit
Authors: Lu Yimin , Huang Xianfeng , He Shaobin , Wang Dongdong , Zhang Bo
Published: January 2015

The memristor is referred to as the fourth fundamental passive circuit element of which inherent nonlinear properties offer to construct the chaos circuits. In this paper, a flux-controlled memristor circuit is developed, and then a van der Pol oscillator is implemented based on this new memristor circuit. The stability of the circuit, the occurring conditions of Hopf bifurcation and limit circle of the self-excited oscillation are analyzed; meanwhile, under the condition of the circuit with an external exciting source, the circuit exhibits a complicated nonlinear dynamic behavior, and chaos occurs within a certain parameter set. The memristor based van der Pol oscillator, furthermore, has been created by an analog circuit utilizing active elements, and there is a good agreement between the circuit responses and numerical simulations of the van der Pol equation. In the consequence, a new approach has been proposed to generate chaos within a nonautonomous circuit system.
Impulsive Control and Synchronization of Memristor-Based Chaotic Circuits
Authors: Yang Shiju , Li Chuandong , Huang Tingwen
Published: January 2015

The memristor is a novel nonlinear passive circuit element which has the memory function, and the circuits based on the memristors might exhibit chaotic behavior. In this paper, we revisit a memristor-based chaotic circuit, and then investigate its stabilization and synchronization via impulsive control. By impulsive system theory, some sufficient conditions for the stabilization and synchronization of the memristor-based chaotic system are established. Moreover, an estimation of the upper bound of the impulse interval is proposed under the condition that the parameters of the chaotic system and the impulsive control law are well defined. To show the effectiveness of the theoretical results, numerical simulations are also presented.
Thermal Modeling of Disc Brake Rotor in Frictional Contact
Authors: Ali Belhocine , Ghazaly Nouby Mahdi
Published: January 2015

Safety aspect in automotive engineering has been considered as a number one priority in development of new vehicle. Each single system has been studied and developed in order to meet safety requirement. Instead of having air bag, good suspension systems, good handling and safe cornering, there is one most critical system in the vehicle which is brake systems. The objective of this work is to investigate and analyze the temperature distribution of rotor disc during braking operation using ANSYS Multiphysics. The work uses the finite element analysis techniques to predict the temperature distribution on the full and ventilated brake disc and to identify the critical temperature of the rotor. The analysis also gives us, the heat flux distribution for the two discs.
Revealing the Participation Inequality in Mobile Location Based Games
Authors: Lund Kate , Coulton Paul , Wilson Andrew
Published: January 2015

Free All Monsters! is a novel, context-aware, location-based mobile game and associated online Web-based portal, which allows players to create content that populates the game. The concept has recently transitioned from an initial prototype debuted at very specific events to an iPhone application that will allow the game to be played anywhere in the world. In this paper we present ongoing research that considers the design issues when location-based games have to accommodate the necessary increase of scale, how emergent behavior manifests within the game, and whether the notion of participation inequality is equally evident in such a system. The results show how new game behavior is emerging from the original prototype and that participation inequality is evident in terms of player profiles. Using these results, suggestions are proposed regarding how designers might overcome such effects.
1
Shape Segmentation by Approximate Convexity Analysis
Authors: Kaick Oliver Van , Fish Noa , Kleiman Yanir , Asafi Shmuel , Cohen-OR Daniel
Published: January 2015

We present a shape segmentation method for complete and incomplete shapes. The key idea is to directly optimize the decomposition based on a characterization of the expected geometry of a part in a shape. Rather than setting the number of parts in advance, we search for the smallest number of parts that admit the geometric characterization of the parts. The segmentation is based on an
intermediate-level
analysis, where first the shape is decomposed into approximate convex components, which are then merged into consistent parts based on a nonlocal geometric signature. Our method is designed to handle incomplete shapes, represented by point clouds. We show segmentation results on shapes acquired by a range scanner, and an analysis of the robustness of our method to missing regions. Moreover, our method yields results that are comparable to state-of-the-art techniques evaluated on complete shapes.
Impediments to Regulatory Compliance of Requirements in Contractual Systems Engineering Projects
Authors: Nekvi Md Rashed I. , Madhavji Nazim H.
Published: January 2015

Large-scale contractual systems engineering projects often need to comply with myriad government regulations and standards as part of contractual obligations. A key activity in the requirements engineering (RE) process for such a project is to demonstrate that all relevant requirements have been elicited from the regulatory documents and have been traced to the contract as well as to the target system components. That is, the requirements have met regulatory compliance. However, there are impediments to achieving this level of compliance due to such complexity factors as voluminous contract, large number of regulatory documents, and multiple domains of the system. Little empirical research has been conducted in the scientific community on identifying these impediments. Knowing these impediments is a driver for change in the solutions domain (i.e., creating improved or new methods, tools, processes, etc.) to deal with such impediments. Through a case study of an industrial RE project, we have identified a number of key impediments to achieving regulatory compliance in a large-scale, complex, systems engineering project. This project is an upgrade of a rail infrastructure system. The key contribution of the article is a number of hitherto uncovered impediments described in qualitative and quantitative terms. The article also describes an artefact model, depicting key artefacts and relationships involved in such a compliance project. This model was created from data gathered and observations made in this compliance project. In addition, the article describes emergent metrics on regulatory compliance of requirements that can possibly be used for estimating the effort needed to achieve regulatory compliance of system requirements.
Mining Agents’ Goals in Agent-Oriented Business Processes
Authors: Yan Jiaqi , Hu Daning , Liao Stephen S. , Wang Huaiqing
Published: January 2015

When designing a business process, individual agents are assigned to perform tasks based on certain goals (i.e., designed process goals). However, based on their own interests, real-world agents often have different goals (i.e., agents’ goals) and thus may behave differently than designed, often resulting in reduced effectiveness or efficiencies of the executed process. Moreover, existing business process research lacks effective methods for discovering agents’ goals in the actual execution of the designed business processes. To address this problem, we propose an agent-oriented goal mining approach to modeling, discovering, and analyzing agents’ goals in executed business processes using historical event logs and domain data. To the best of our knowledge, our research is the first to adopt the agents’ goal perspective to study inconsistencies between the design and execution of business processes. Moreover, it also provides a useful tool for stakeholders to discover real-world agents’ actual goals and thus provides insights for improving the task assignment mechanism or business process design in general.
A Reconfigurable Architecture for Binary Acceleration of Loops with Memory Accesses
Authors: Paulino Nuno , Ferreira João Canas , Cardoso João M. P.
Published: January 2015

This article presents a reconfigurable hardware/software architecture for binary acceleration of embedded applications. A Reconfigurable Processing Unit (RPU) is used as a coprocessor of the General Purpose Processor (GPP) to accelerate the execution of repetitive instruction sequences called
Megablocks
. A toolchain detects Megablocks from instruction traces and generates customized RPU implementations. The implementation of Megablocks with memory accesses uses a memory-sharing mechanism to support concurrent accesses to the entire address space of the GPP’s data memory. The scheduling of load/store operations and memory access handling have been optimized to minimize the latency introduced by memory accesses. The system is able to dynamically switch the execution between the GPP and the RPU when executing the original binaries of the input application. Our proof-of-concept prototype achieved geometric mean speedups of 1.60× and 1.18× for, respectively, a set of 37 benchmarks and a subset considering the 9 most complex benchmarks. With respect to a previous version of our approach, we achieved geometric mean speedup improvements from 1.22 to 1.53 for the 10 benchmarks previously used.
Discovering XSD Keys from XML Data
Authors: Arenas Marcelo , Daenen Jonny , Neven Frank , Ugarte Martin , Bussche Jan Van Den , Vansummeren Stijn
Published: January 2015

A great deal of research into the learning of schemas from XML data has been conducted in recent years to enable the automatic discovery of XML schemas from XML documents when no schema or only a low-quality one is available. Unfortunately, and in strong contrast to, for instance, the relational model, the automatic discovery of even the simplest of XML constraints, namely XML keys, has been left largely unexplored in this context. A major obstacle here is the unavailability of a theory on reasoning about XML keys in the presence of XML schemas, which is needed to validate the quality of candidate keys. The present article embarks on a fundamental study of such a theory and classifies the complexity of several crucial properties concerning XML keys in the presence of an XSD, like, for instance, testing for consistency, boundedness, satisfiability, universality, and equivalence. Of independent interest, novel results are obtained related to cardinality estimation of XPath result sets. A mining algorithm is then developed within the framework of levelwise search. The algorithm leverages known discovery algorithms for functional dependencies in the relational model, but incorporates the properties mentioned before to assess and refine the quality of derived keys. An experimental study on an extensive body of real-world XML data evaluating the effectiveness of the proposed algorithm is provided.
A Rule-Based Design Specification Language for Synthetic Biology
Authors: Oberortner Ernst , Bhatia Swapnil , Lindgren Erik , Densmore Douglas
Published: January 2015

Synthetic Biology is an engineering discipline where parts of DNA sequences are composed into novel, complex systems that execute a desired biological function. Functioning and well-behaving biological systems adhere to a certain set of biological “rules”. Data exchange standards and Bio-Design Automation (BDA) tools support the organization of part libraries and the exploration of rule-compliant compositions. In this work, we formally define a design specification language, enabling the integration of biological rules into the Synthetic Biology engineering process. The supported rules are divided into five categories:
Counting
,
Pairing
,
Positioning
,
Orientation
, and
Interactions
. We formally define the semantics of each rule, characterize the language's expressive power, and perform a case study in that we iteratively design a genetic Priority Encoder circuit following two alternative paradigms—rule-based and template-driven. Ultimately, we touch a method to approximate the complexity and time to computationally enumerate all rule-compliant designs. Our specification language may or may not be expressive enough to capture all designs that a Synthetic Biologist might want to describe, or the complexity one might find through experiments. However, computational support for the acquisition, specification, management, and application of biological rules is inevitable to understand the functioning of biology.
Beating Shapes Relying on Moiré Level Lines
Authors: Chosson Sylvain M. , Hersch Roger D.
Published: January 2015

We consider the problem of obtaining a recognizable shape as superposition moiré of two line gratings. The method we propose generates moiré lines located between the shape foreground and background centers and the shape boundaries. Upon relative displacement of the superposed base- and revealing-layer gratings, the moiré lines move and give the impression of beating shapes. Original bilevel shapes are converted into elevation profiles that are embedded by small local shifts within the base-layer grating layout. The elevation profile's level lines are revealed as moiré by superposing the base and revealing layers. Similar level line moirés can be obtained by applying an identical geometric transformation to both the base and the revealing layers. In order to create grayscale or color images embedding several distinct moiré shapes, we create as base layer a dither array made of several ditherband gratings, each one embedding its specific elevation profile. Further variants include the possibility of incorporating elevation profiles within both the base and the revealing layers, or having two elevation profiles sharing a same base layer by tiling the available space. The moiré-level line techniques can be advantageously used for decorative or for anti-counterfeiting applications. Their base- and revealing-layer gratings may be produced by printing techniques, by imaging on film, or by arrays of cylindrical microlenses.
Stochastic Model Checking of Genetic Circuits
Authors: Madsen Curtis , Zhang Zhen , Roehner Nicholas , Winstead Chris , Myers Chris
Published: January 2015

Synthetic genetic circuits have a number of exciting potential applications such as cleaning up toxic waste, hunting and killing tumor cells, and producing drugs and bio-fuels more efficiently. When designing and analyzing genetic circuits, researchers are often interested in the probability of observing certain behaviors. Discerning these probabilities typically involves simulating the circuit to produce some time series data and computing statistics over the resulting data. However, for very rare behaviors of complex genetic circuits, it becomes computationally intractable to obtain good results as the number of required simulation runs grows exponentially. It is, therefore, necessary to apply numerical methods to determine these probabilities directly. This article describes how
stochastic model checking
, a method for determining the likelihood that certain events occur in a system, can by applied to models of genetic circuits by translating them into
continuous-time Markov chains
(CTMCs) and analyzing them using
Markov chain analysis
to check
continuous stochastic logic
(CSL) properties. The utility of this approach is demonstrated with several case studies illustrating how this method can be used to perform design space exploration of two genetic oscillators and two genetic state-holding elements. Our results show that this method results in a substantial speedup as compared with conventional simulation-based approaches.
Residual Investigation
Authors: Li Kaituo , Reichenbach Christoph , Csallner Christoph , Smaragdakis Yannis
Published: January 2015

We introduce the concept of
residual investigation
for program analysis. A residual investigation is a dynamic check installed as a result of running a static analysis that reports a possible program error. The purpose is to observe conditions that indicate whether the statically predicted program fault is likely to be realizable and relevant. The key feature of a residual investigation is that it has to be much more precise (i.e., with fewer false warnings) than the static analysis alone, yet significantly more general (i.e., reporting more errors) than the dynamic tests in the program's test suite that are pertinent to the statically reported error. That is, good residual investigations encode dynamic conditions that, when considered in conjunction with the static error report, increase confidence in the existence or severity of an error without needing to directly observe a fault resulting from the error.

We enhance the static analyzer FindBugs with several residual investigations appropriately tuned to the static error patterns in FindBugs, and apply it to nine large open-source systems and their native test suites. The result is an analysis with a low occurrence of false warnings (false positives) while reporting several actual errors that would not have been detected by mere execution of a program's test suite.
Interactive intent modeling
Authors: Ruotsalo Tuukka , Jacucci Giulio , Myllymäki Petri , Kaski Samuel
Published: January 2015

The system should let users incrementally direct their search toward relevant, though not initially obvious, information.
Fluigi
Authors: Huang Haiyao , Densmore Douglas
Published: January 2015

One goal of synthetic biology is to design and build genetic circuits in living cells for a range of applications. Our incomplete knowledge of the effects of metabolic load and biological “crosstalk” on the host cell make it difficult to construct multilevel genetic logic circuits in a single cell, limiting the scalability of engineered biological systems. Microfluidic technologies provide reliable and scalable construction of synthetic biological systems by allowing compartmentalization of cells encoding simple genetic circuits and the spatiotemporal control of communication among these cells. This control is achieved via valves on the microfluidics chip which restrict fluid flow when activated. We describe a Computer Aided Design (CAD) framework called “Fluigi” for optimizing the layout of genetic circuits on a microfluidic chip, generating the control sequence of the associated signaling fluid valves, and simulating the behavior of the configured biological circuits. We demonstrate the capabilities of Fluigi on a set of Boolean algebraic benchmark circuits found in both synthetic biology and electrical engineering and a set of assay-based benchmark circuits. The integration of microfluidics and synthetic biology has the capability to increase the scale of engineered biological systems for applications in DNA assembly, biosensors, and screening assays for novel orthogonal genetic parts.
Parallel Networks
Authors: Deans Tara L.
Published: January 2015

Synthetic biology has emerged as an important technology for engineering cells to behave in controllable and predictable ways. The promise of this modern technology is dependent on our understanding of cellular complexity to allow us to engineer cells with novel function. In this regard, the fields of computer science and synthetic biology are critical for accelerating both our understanding of biological systems, and our ability to quantitatively engineer cells. Thus, advances in biology and biotechnology are arising at the intersection of computer science and synthetic biology approaches. This review seeks to introduce the field of synthetic biology to the computer science community, and to ignite a curiosity and interest in fostering a unique synergy for possible collaborations between synthetic biologists and computer scientists.
Introduction to the Special Issue on Computational Synthetic Biology
Authors: Myers Chris J. , Sauro Herbert , Wipat Anil
Published: January 2015

The goal of this special issue is to introduce the field of computational synthetic biology to engineers and computer scientists. The first article gives an introduction to the key biological principles and experimental techniques that support synthetic biology, and it draws analogies with the computing field. This issue also includes five original research articles in computational synthetic biology. The first research article discusses how standards can be used to modularize the design process for genetic circuits. The next two articles introduce new abstraction techniques to improve the efficiency of analysis of genetic circuit models. The last two articles introduce new design techniques that help decouple design from construction. We hope this sampling from the field will help to motivate others to join this exciting and rich area of research.
Opportunities of social media in health and well-being
Authors: De Choudhury Munmun
Published: January 2015

Intelligently leveraging data from millions of social media posts is a modern public health approach that has the potential to save many lives.
Children Programming Games
Authors: Werner Linda , Denner Jill , Campe Shannon
Published: January 2015

This article reports the results of a study of the relationship of computer game programming to computational learning (CL). The results contribute to the growing body of knowledge about how to define and measure CL among children by proposing a new concept, Game Computational Sophistication (GCS). We analyzed 231 games programmed by 325 11 and 12 year olds with a range of prior computer experience who attended a voluntary technology class during or after school. Findings suggest that students’ games exhibited a range of GCS: programs composed of sequences of simple programming constructs; programs composed of programming constructs, some of which are used to implement higher-order patterns; and programs composed of game mechanics built from combinations of patterns “glued” together with simple programming constructs. We use case studies of students’ games to illustrate how variation in the use and integration of programming constructs, patterns, and game mechanics can be used to demonstrate evidence of CL. The study contributes to an understanding of what CL looks like in middle school, how to assess it, and how game-programming activities might promote CL.
Challenges in personal health tracking
Authors: Kay Matthew
Published: January 2015

Increasingly, personal health data can be tracked and integrated from numerous streams quickly and easily, but our feedback lingers in the land of "show the user a graph and hope." How can we help people make sense of personal health data?
Light Field Reconstruction Using Sparsity in the Continuous Fourier Domain
Authors: Shi Lixin , Hassanieh Haitham , Davis Abe , Katabi Dina , Durand Fredo
Published: January 2015

Sparsity in the Fourier domain is an important property that enables the dense reconstruction of signals, such as 4D light fields, from a small set of samples. The sparsity of natural spectra is often derived from continuous arguments, but reconstruction algorithms typically work in the discrete Fourier domain. These algorithms usually assume that sparsity derived from continuous principles will hold under discrete sampling. This article makes the critical observation that sparsity is much greater in the
continuous
Fourier spectrum than in the
discrete
spectrum. This difference is caused by a windowing effect. When we sample a signal over a finite window, we convolve its spectrum by an infinite sinc, which destroys much of the sparsity that was in the continuous domain. Based on this observation, we propose an approach to reconstruction that optimizes for sparsity in the continuous Fourier spectrum. We describe the theory behind our approach and discuss how it can be used to reduce sampling requirements and improve reconstruction quality. Finally, we demonstrate the power of our approach by showing how it can be applied to the task of recovering non-Lambertian light fields from a small number of 1D viewpoint trajectories.
Formal Verification of Software Countermeasures against Side-Channel Attacks
Authors: Eldib Hassan , Wang Chao , Schaumont Patrick
Published: January 2015

A common strategy for designing countermeasures against power-analysis-based side-channel attacks is using
random masking
techniques to remove the statistical dependency between sensitive data and side-channel emissions. However, this process is both labor intensive and error prone and, currently, there is a lack of automated tools to formally assess how secure a countermeasure really is. We propose the first SMT-solver-based method for formally verifying the security of a masking countermeasure against such attacks. In addition to checking whether the sensitive data are
masked
by random variables, we also check whether they are
perfectly masked
, that is, whether the intermediate computation results in the implementation of a cryptographic algorithm are independent of the secret key. We encode this verification problem using a series of quantifier-free first-order logic formulas, whose satisfiability can be decided by an off-the-shelf SMT solver. We have implemented the proposed method in a software verification tool based on the LLVM compiler frontend and the Yices SMT solver. Our experiments on a set of recently proposed masking countermeasures for cryptographic algorithms such as AES and MAC-Keccak show the method is both effective in detecting power side-channel leaks and scalable for practical use.
A valuable lesson, and whither Hadoop?
Authors: Barr Valerie , Stonebraker Michael
Published: January 2015

The
Communications
Web site, http://cacm.acm.org, features more than a dozen bloggers in the BLOG@CACM community. In each issue of
Communications
, we'll publish selected posts or excerpts.

twitter

Follow us on Twitter at http://twitter.com/blogCACM

http://cacm.acm.org/blogs/blog-cacm

Valerie Barr considers outcomes from the Grace Hopper Celebration, while Michael Stonebraker ponders the past, present, and possible future of the "Hadoop stack."
A Theory of Pricing Private Data
Authors: Li Chao , Li Daniel Yang , Miklau Gerome , Suciu Dan
Published: January 2015

Personal data has value to both its owner and to institutions who would like to analyze it. Privacy mechanisms protect the owner's data while releasing to analysts noisy versions of aggregate query results. But such strict protections of the individual's data have not yet found wide use in practice. Instead, Internet companies, for example, commonly provide free services in return for valuable sensitive information from users, which they exploit and sometimes sell to third parties.

As awareness of the value of personal data increases, so has the drive to compensate the end-user for her private information. The idea of monetizing private data can improve over the narrower view of hiding private data, since it empowers individuals to control their data through financial means.

In this article we propose a theoretical framework for assigning prices to noisy query answers as a function of their accuracy, and for dividing the price amongst data owners who deserve compensation for their loss of privacy. Our framework adopts and extends key principles from both differential privacy and query pricing in data markets. We identify essential properties of the pricing function and micropayments, and characterize valid solutions.
Here comes the #engagement: A serious health initiative made trendy
Authors: Payton Fay Cobb , Galloway KaMar
Published: January 2015

Creating a user experience to communicate the seriousness of HIV prevention and awareness can be both educational while entertaining. This combination along with a sense of cultural influence helps to both attract and engage millennials.
Visualization for Relevance Assessments
Authors: Alonso Omar
Published: January 2015

Visual data exploration is a well-known technique in the data mining toolbox for analyzing and understanding large amounts of data. In information retrieval, visualization is still perceived as a front-end or user facing feature while, at the same time, it can be very effective in the back-end for data analysis. Currently, the research community does not sufficiently analyze the reasons underlying the assessments they use for evaluation, which may lead to bias or error when reporting system performance. In this paper we examine the integration of information visualization techniques for visually exploring and analyzing relevance assessments. We argue that visual tools should be integrated as a core component of the infrastructure for relevance assessment and evaluation.
Report on the SIGIR 2014 Workshop on Medical Information Retrieval (MedIR)
Authors: Goeuriot Lorraine , Kelly Liadh , Jones Gareth J.F. , Müller Henning , Zobel Justin
Published: January 2015

The workshop on Medical Information Retrieval took place at SIGIR 2014 in Gold Coast, Australia on July 11. The workshop included eight oral presentations of referred papers and an invited keynote presentation. This allowed time for lively discussions among the participants. These showed the significant interest in the medical information retrieval domain and the many research challenges arising in this space which need to be addressed to give added value to the wide variety of users that can profit from medical information search, such as patients, general health professionals and specialist groups such as radiologists who mainly search for images and image related information.
Report on the 1st International Workshop on Information Access in Smart Cities (i-ASC 2014)
Authors: Albakour M-Dyaa , Macdonald Craig , Ounis Iadh , Clarke Charles L.A. , Bicer Veli
Published: January 2015

Modern cities are increasingly becoming smart where a digital knowledge infrastructure is deployed by local authorities (e.g. City councils and municipalities) to better serve the information needs of their citizens, and to ensure the sustainability and efficient use of power and resources. This knowledge infrastructure consists of a wide range of systems from lowlevel physical sensors to advanced sensing devices through social sensors. The i-ASC 2014 workshop was the first international event, within the Information Retrieval (IR) community, that is dedicated to research on smart/future cities. In particular, the workshop was a venue for research on digesting the city's data streams and knowledge databases in order to serve the information needs of citizens and support decision making for local authorities. Possible use cases include helping tourists to find interesting places to go or activities to do while visiting a city, or assisting journalists in reporting local incidents. Indeed, the workshop was intended to foster the development of new information access and retrieval models that can harness effectively and efficiently the large number of heterogeneous big data streams in a city to provide a new generation of information services. The workshop was well attended, where more than 45 participants were officially registered. It featured two keynote talks from industry (IBM andWaag Society) and two invited talks from academia (Pisa and Edinburgh). In addition, seven refereed papers were presented before breakout groups considered questions and issues identified from a panel discussion.
Alembic
Authors: Holt Brandon , Briggs Preston , Ceze Luis , Oskin Mark
Published: January 2015

Partitioned Global Address Space (PGAS) environments simplify writing parallel code for clusters because they make data movement implicit - dereferencing global pointers automatically moves data around. However, it does not free the programmer from needing to reason about locality - poor placement of data can lead to excessive and even unnecessary communication. For this reason, modern PGAS languages such as X10, Chapel, and UPC allow programmers to express data-layout constraints and explicitly move computation. This places an extra burden on the programmer, and is less effective for applications with limited or data-dependent locality (e.g., graph analytics).

This paper proposes Alembic, a new static analysis that frees programmers from having to manually move computation to exploit locality in PGAS programs. It works by determining regions of code that access the same cluster node, then transforming the code to migrate parts of the execution to increase the proportion of accesses to local data. We implement the analysis and transformation for C++ in LLVM and show that in irregular application kernels, Alembic can achieve 82% of the performance of hand-tuned communication (for comparison, naïve compiler-generated communication achieves only 13%).
Symbolic execution of multithreaded programs from arbitrary program contexts
Authors: Bergan Tom , Grossman Dan , Ceze Luis
Published: January 2015

We describe an algorithm to perform symbolic execution of a multithreaded program starting from an arbitrary program context. We argue that this can enable more efficient symbolic exploration of deep code paths in multithreaded programs by allowing the symbolic engine to jump directly to program contexts of interest.

The key challenge is modeling the initial context with reasonable precision - an overly approximate model leads to exploration of many infeasible paths during symbolic execution, while a very precise model would be so expensive to compute that computing it would defeat the purpose of jumping directly to the initial context in the first place. We propose a
context-specific dataflow analysis
that approximates the initial context cheaply, but precisely enough to avoid some common causes of infeasible-path explosion. This model is necessarily approximate - it may leave portions of the memory state unconstrained, leaving our symbolic execution unable to answer simple questions such as "which thread holds lock A?". For such cases, we describe a novel algorithm for evaluating
symbolic synchronization
during symbolic execution. Our symbolic execution semantics are sound and complete up to the limits of the underlying SMT solver. We describe initial experiments on an implementation in Cloud 9.
Continuously measuring critical section pressure with the free-lunch profiler
Authors: David Florian , Thomas Gael , Lawall Julia , Muller Gilles
Published: January 2015

Today, Java is regularly used to implement large multi-threaded server-class applications that use locks to protect access to shared data. However, understanding the impact of locks on the performance of a system is complex, and thus the use of locks can impede the progress of threads on configurations that were not anticipated by the developer, during specific phases of the execution.

In this paper, we propose Free Lunch, a new lock profiler for Java application servers, specifically designed to identify, in-vivo, phases where the progress of the threads is impeded by a lock. Free Lunch is designed around a new metric, critical section pressure (CSP), which directly correlates the progress of the threads to each of the locks. Using Free Lunch, we have identified phases of high CSP, which were hidden with other lock profilers, in the distributed Cassandra NoSQL database and in several applications from the DaCapo 9.12, the SPECjvm2008 and the SPECjbb2005 benchmark suites. Our evaluation of Free Lunch shows that its overhead is never greater than 6%, making it suitable for in-vivo use.
Efficient subcubic alias analysis for C
Authors: Zhang Qirun , Xiao Xiao , Zhang Charles , Yuan Hao , Su Zhendong
Published: January 2015

Inclusion-based alias analysis for C can be formulated as a context-free language (CFL) reachability problem. It is well known that the traditional cubic CFL-reachability algorithm does not scale well in practice. We present a highly scalable and efficient CFL-reachability-based alias analysis for C. The key novelty of our algorithm is to propagate reachability information along only original graph edges and bypass a large portion of summary edges, while the traditional CFL-reachability algorithm propagates along all summary edges. We also utilize the Four Russians' Trick - a key enabling technique in the subcubic CFL-reachability algorithm - in our alias analysis. We have implemented our subcubic alias analysis and conducted extensive experiments on widely-used C programs from the pointer analysis literature. The results demonstrate that our alias analysis scales extremely well in practice. In particular, it can analyze the recent Linux kernel (which consists of 10M SLOC) in about 30 seconds.
Determinacy in static analysis for jQuery
Authors: Andreasen Esben , Møller Anders
Published: January 2015

Static analysis for JavaScript can potentially help programmers find errors early during development. Although much progress has been made on analysis techniques, a major obstacle is the prevalence of libraries, in particular jQuery, which apply programming patterns that have detrimental consequences on the analysis precision and performance. Previous work on dynamic determinacy analysis has demonstrated how information about program expressions that always resolve to a fixed value in some call context may lead to significant scalability improvements of static analysis for such code. We present a static dataflow analysis for JavaScript that infers and exploits determinacy information on-the-fly, to enable analysis of some of the most complex parts of jQuery. The analysis combines selective context and path sensitivity, constant propagation, and branch pruning, based on a systematic investigation of the main causes of analysis imprecision when using a more basic analysis.

The techniques are implemented in the TAJS analysis tool and evaluated on a collection of small programs that use jQuery. Our results show that the proposed analysis techniques boost both precision and performance, specifically for inferring type information and call graphs.
Rubah
Authors: Pina Luís , Veiga Luís , Hicks Michael
Published: January 2015

This paper presents Rubah, the first
dynamic software updating
system for Java that: is
portable
, implemented via libraries and bytecode rewriting on top of a standard JVM; is
efficient
, imposing essentially no overhead on normal, steady-state execution; is
flexible
, allowing nearly arbitrary changes to classes between updates; and is
non-disruptive
, employing either a novel eager algorithm that transforms the program state with multiple threads, or a novel lazy algorithm that transforms objects as they are demanded, post-update. Requiring little programmer effort, Rubah has been used to dynamically update five long-running applications: the H2 database, the Voldemort key-value store, the Jake2 implementation of the Quake 2 shooter game, the CrossFTP server, and the JavaEmailServer.
Accelerating iterators in optimizing AST interpreters
Authors: Zhang Wei , Larsen Per , Brunthaler Stefan , Franz Michael
Published: January 2015

Generators offer an elegant way to express iterators. However, their performance has always been their Achilles heel and has prevented widespread adoption. We present techniques to efficiently implement and optimize generators.

We have implemented our optimizations in ZipPy, a modern, light-weight AST interpreter based Python 3 implementation targeting the Java virtual machine. Our implementation builds on a framework that optimizes AST interpreters using just-in-time compilation. In such a system, it is crucial that AST optimizations do not prevent subsequent optimizations. Our system was carefully designed to avoid this problem. We report an average speedup of 3.58x for generator-bound programs. As a result, using generators no longer has downsides and programmers are free to enjoy their upsides.
Atlas
Authors: Chakrabarti Dhruva R. , Boehm Hans-J. , Bhandari Kumud
Published: January 2015

Non-volatile main memory, such as memristors or phase change memory, can revolutionize the way programs persist data. In-memory objects can themselves be persistent without the need for a separate persistent data storage format. However, the challenge is to ensure that such data remains consistent if a failure occurs during execution.

In this paper, we present our system, called Atlas, which adds durability semantics to lock-based code, typically allowing us to automatically maintain a globally consistent state even in the presence of failures. We identify failure-atomic sections of code based on existing critical sections and describe a log-based implementation that can be used to recover a consistent state after a failure. We discuss several subtle semantic issues and implementation tradeoffs. We confirm the ability to rapidly flush CPU caches as a core implementation bottleneck and suggest partial solutions. Experimental results confirm the practicality of our approach and provide insight into the overheads of such a system.
EventBreak
Authors: Pradel Michael , Schuh Parker , Necula George , Sen Koushik
Published: January 2015

Event-driven user interface applications typically have a single thread of execution that processes event handlers in response to input events triggered by the user, the network, or other applications. Programmers must ensure that event handlers terminate after a short amount of time because otherwise, the application may become unresponsive. This paper presents EventBreak, a performance-guided test generation technique to identify and analyze event handlers whose execution time may gradually increase while using the application. The key idea is to systematically search for pairs of events where triggering one event increases the execution time of the other event. For example, this situation may happen because one event accumulates data that is processed by the other event. We implement the approach for JavaScript-based web applications and apply it to three real-world applications. EventBreak discovers events with an execution time that gradually increases in an unbounded way, which makes the application unresponsive, and events that, if triggered repeatedly, reveal a severe scalability problem, which makes the application unusable. The approach reveals two known bugs and four previously unknown responsiveness problems. Furthermore, we show that EventBreak helps in testing that event handlers avoid such problems by bounding a handler's execution time.
Understanding energy behaviors of thread management constructs
Authors: Pinto Gustavo , Castor Fernando , Liu Yu David
Published: January 2015

Java programmers are faced with numerous choices in managing concurrent execution on multicore platforms. These choices often have different trade-offs (e.g., performance, scalability, and correctness guarantees). This paper analyzes an additional dimension, energy consumption. It presents an empirical study aiming to illuminate the relationship between the choices and settings of thread management constructs and energy consumption. We consider three important thread management constructs in concurrent programming: explicit thread creation, fixed-size thread pooling, and work stealing. We further shed light on the energy/performance trade-off of three ``tuning knobs'' of these constructs: the number of threads, the task division strategy, and the characteristics of processed data. Through an extensive experimental space exploration over real-world Java programs, we produce a list of findings about the energy behaviors of concurrent programs, which are not always obvious. The study serves as a first step toward improving energy efficiency of concurrent programs on parallel architectures.