bluuebunny/crossref_metadata_2025 huggingface dataset:
Outgassing rate measurements of stainless steel and polymers using the difference method
Authors: Battes Katharina , Day Christian , Hauer Volker
Published: January 2015

This paper presents a new outgassing test facility based on the difference method, which is a rarely used modified throughput technique. Furthermore, the experimental approach presented is validated based on new measurement data for three relevant materials. The facility allows to measure at a good resolution thermal outgassing rates at variable temperatures between room temperature and 300 °C. The measurement approach is discussed, the facility is described, and the measurement uncertainty is evaluated. Three materials were measured to demonstrate the new experimental approach and to compare the results obtained for stainless steel 316L and two polymers, Viton® and Vespel®. For stainless steel 316L, the influence of different pretreatments was analyzed. It was found that by baking in vacuum as well as in air (400 °C, 100 h), the outgassing rate can be reduced by almost a factor of ten, in line with predictions based on outgassing theory. The polymers were investigated, as they represent materials with quite large outgassing rates. This was confirmed, especially when they were measured as received, without baking. In general, the difference method for measuring thermal outgassing was found to work well in a wide range of outgassing rates.
Robust primary modulation‐based scatter estimation for cone‐beam CT
Authors: Ritschl Ludwig , Fahrig Rebecca , Knaup Michael , Maier Joscha , Kachelrieß Marc
Published: January 2015

Purpose:

Scattered radiation is one of the major problems facing image quality in flat detector cone‐beam computed tomography (CBCT). Previously, a new scatter estimation and correction method using primary beam modulation has been proposed. The original image processing technique used a frequency‐domain‐based analysis, which proved to be sensitive to the accuracy of the modulator pattern both spatially and in amplitude as well as to the frequency of the modulation pattern. In addition, it cannot account for penumbra effects that occur, for example, due to the finite focal spot size and the scatter estimate can be degraded by high‐frequency components of the primary image.

Methods:

In this paper, the authors present a new way to estimate the scatter using primary modulation. It is less sensitive to modulator nonidealities and most importantly can handle arbitrary modulator shapes and changes in modulator attenuation. The main idea is that the scatter estimation can be expressed as an optimization problem, which yields a separation of the scatter and the primary image. The method is evaluated using simulated and experimental CBCT data. The scattering properties of the modulator itself are analyzed using a Monte Carlo simulation.

Results:

All reconstructions show strong improvements of image quality. To quantify the results, all images are compared to reference images (ideal simulations and collimated scans).

Conclusions:

The proposed modulator‐based scatter reduction algorithm may open the field of flat detector‐based imaging to become a quantitative modality. This may have significant impact on C‐arm imaging and on image‐guided radiation therapy.
Performance characterization of high quantum efficiency metal package photomultiplier tubes for time‐of‐flight and high‐resolution PET applications
Authors: Ko Guen Bae , Lee Jae Sung
Published: January 2015

Purpose:

Metal package photomultiplier tubes (PMTs) with a metal channel dynode structure have several advanced features for devising such time‐of‐flight (TOF) and high spatial resolution positron emission tomography (PET) detectors, thanks to their high packing density, large effective area ratio, fast time response, and position encoding capability. Here, we report on an investigation of new metal package PMTs with high quantum efficiency (QE) for high‐resolution PET and TOF PET detector modules.

Methods:

The latest metal package PMT, the Hamamatsu R11265 series, is served with two kinds of photocathodes that have higher quantum efficiency than normal bialkali (typical QE ≈ 25%), super bialkali (SBA; QE ≈ 35%), and ultra bialkali (UBA; QE ≈ 43%). In this study, the authors evaluated the performance of the new PMTs with SBA and UBA photocathodes as a PET detector by coupling various crystal arrays. They also investigated the performance improvements of high QE, focusing in particular on a block detector coupled with a lutetium‐based scintillator. A single 4 × 4 × 10 mm3 LYSO, a 7 × 7 array of 3 × 3 × 20 mm3 LGSO, a 9 × 9 array of 1.2 × 1.2 × 10 mm3 LYSO, and a 6 × 6 array of 1.5 × 1.5 × 7 mm3 LuYAP were used for evaluation. All coincidence data were acquired with a DRS4 based fast digitizer.

Results:

This new PMT shows promising crystal positioning accuracy, energy and time discrimination performance for TOF, and high‐resolution PET applications. The authors also found that a metal channel PMT with SBA was enough for both TOF and high‐resolution application, although UBA gave a minor improvement to time resolution. However, significant performance improvement was observed in relative low light output crystals (LuYAP) coupled with UBA.

Conclusions:

The results of this study will be of value as a useful reference to select PMTs for high‐performance PET detectors.
Physical Demands and Salivary Immunoglobulin A Responses of Elite Australian Rules Football Athletes to Match Play
Authors: Coad Sam , Gray Bon , Wehbe George , McLellan Christopher
Published: January 2015

Purpose:

To examine the response or pre- and postmatch salivary immunoglobulin A concentration ([s-IgA]) to Australian Football League (AFL) match play and investigate the acute and cumulative influence of player workload and postmatch [s-IgA] after repeated participation in AFL match play.

Methods:

Eleven elite AFL athletes (21.8 ± 2.4 y, 186.9 ± 7.9 cm, 87.4 ± 7.5 kg) were monitored throughout 3 matches during the preseason that were separated by 7 d. Saliva samples were collected across each AFL match at 24 h and 1 h prematch and 1, 12, 36, and 60 h postmatch to determine [s-IgA]. Global positioning systems (GPS) with integrated triaxial accelerometers were used to determine total player workload during match play. Hypothesis testing was conducted for time-dependent changes in [s-IgA] and player load using a repeated-measures ANOVA.

Results:

Player load during match 3 (1266 ± 124.6 AU) was significantly (P < .01) greater than in match 1 (1096 ± 115.1 AU) and match 2 (1082 ± 90.4 AU). Across match 3, [s-IgA] was significantly (P < .01) suppressed at 2 postmatch measures (12 and 36 h) compared with prematch measures (24 and 1 h), which coincided with significantly (P < .01) elevated player load.

Conclusion:

The findings indicate that an increase in player load during AFL preseason match play resulted in compromised postmatch mucosal immunological function. Longitudinal assessment of AFL-match player load and mucosal immunological function across the first 60 h of recovery may augment monitoring and preparedness strategies for athletes.
An Exploration of Sports Rehabilitators’ and Athletic Rehabilitation Therapists’ Views on Fear of Reinjury After Anterior Cruciate Ligament Reconstruction
Authors: McVeigh Fiona , Pack Stephen M.
Published: January 2015

Background:

Research involving long-term follow-up of patients after successful anterior cruciate ligament reconstruction (ACLR) has shown that return-to-sport rates are not as good as would be expected despite many patients’ having normal knee-function scores. The psychological component, specifically fear of reinjury, plays a critical role in determining patients’ return to play and is frequently underestimated. Little is known about the recognition and intervention from the therapist’s perspective.

Aim:

To gain a greater understanding of the views of sports rehabilitators and athletic rehabilitation therapists on recognition of fear of reinjury in clients after ACLR.

Method and Design:

A qualitative approach, consisting of semistructured interviews with a purposive sample of 8 participants, sports rehabilitators, or athletic rehabilitation therapists. This population has been largely unexamined in this context in previous research.

Main Findings:

Thematic analysis yielded 2 main themes: communication and education. Participants discussed the importance of communication in the client–therapist relationship and how it is used in addressing misinformation and fear of reinjury. All participants used education in outlining the rehabilitation pathway and dealing with those providing social support around the client. Issues emerged relating to therapists’ recognition of observable signs of fear of reinjury in the clinical setting. Overall, participants thought that fear of reinjury was not a barrier to return to play after ACLR.

Conclusion:

There is a need for more education of therapists on recognizing fear of reinjury and the appropriate use of psychological intervention skills as a method for dealing with this throughout the rehabilitation process.
The Effects of Low-Level Laser Therapy on Pain Associated With Tendinopathy: A Critically Appraised Topic
Authors: Doyle Andrew T. , Lauber Christine , Sabine Kendra
Published: January 2015

Clinical Scenario:

Tendinopathies plague many active individuals, causing pain and reducing sport activity by decreasing range of motion and strength. There are many modalities that have been used to treat pain associated with chronic inflammation, such as ultrasound, moist heat packs, and electrical stimulation. Low-level laser therapy (LLLT) is one such modality. Potential benefits of managing pain associated with tendinopathies have been investigated using LLLT. Cellular respiration and metabolism are thought to be increased by LLLT acting on the mitochondrial cytochromes. The effects LLLT may have on cellular activity could increase blood flow to progress the healing process by reducing the pain-spasm cycle. The purpose of this critically appraised topic is to identify the clinical effectiveness of LLLT on pain associated with tendinopathy and to identify the parameters used to achieve statistically and clinically relevant pain outcomes.

Focused Clinical Question:

What is the effect of LLLT on pain associated with tendinopathy?

Clinical Bottom Line:

Although LLLT significantly decreases pain from baseline, its use may be no better than placebo or traditional treatments such as ultrasound, moist heat packs, electrical stimulation, or therapeutic exercise to reduce pain associated with tendinopathy. Total accumulated joules across the treatment sessions may need to be taken into account as a parameter.
MicroRNA regulatory networks in idiopathic pulmonary fibrosis
Authors: Pandit Kusum V. , Milosevic Jadranka
Published: January 2015

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, and fatal scarring lung disease of unknown etiology, characterized by changes in microRNA expression. Activation of transforming growth factor (TGF-β) is a key event in the development of IPF. Recent reports have also identified epigenetic modification as an important player in the pathogenesis of IPF. In this review, we summarize the main results of studies that address the role of microRNAs in IPF and highlight the synergistic actions of these microRNAs in regulating TGF-β, the primary fibrogenic mediator. We outline epigenetic regulation of microRNAs by methylation. Functional studies identify microRNAs that alter proliferative and migratory properties of fibroblasts, and induce phenotypic changes in epithelial cells consistent with epithelial-mesenchymal transition. Though these studies were performed in isolation, we identify multiple co-operative actions after assembling the results into a network. Construction of such networks will help identify disease-propelling hubs that can be targeted for therapeutic purposes.
Angle count sampling reliability as ground truth for area-based LiDAR applications in forest inventories
Authors: Scrinzi Gianfranco , Clementel Fabrizio , Floris Antonio
Published: January 2015

LiDAR-based techniques to estimate forest variables at the stand level require accurate calibration through ground truth data. One purpose of this study was to verify whether angle count samples can be used as suitable ground truth to calibrate LiDAR-based models for timber volume estimation. Volume data were acquired on the ground for 79 plots in the Latemar forest (province of Bolzano, Italian Alps). A simple linear regression model, using the sum of all of the tree canopy heights in the plot as the explanatory variable, was adopted. As angle count samples have no fixed area, three different methods to approximate their size were compared. The angle count sample area can be properly approximated by visual assessment of the tree size classes and by callipering the largest tree in the plot. The results show that angle count sampling can be an efficient solution to calibrate LiDAR-based models: they produced fair estimates at the plot level (relative root mean square error (RMSE), 26.6%) that were better than fixed-radius plot estimates with full callipering (RMSE, 29.7%). Estimate uncertainty at increasingly large forest stand areas was also calculated by means of a simulation procedure. It showed that low uncertainty (standard error of estimate = approximately 2%) could be reached at a forest compartment level (19 ha on average).
Classification of Bifurcations of Quasi-Periodic Solutions Using Lyapunov Bundles
Authors: Kamiyama Kyohei , Komuro Motomasa , Endo Tetsuro , Aihara Kazuyuki
Published: January 2015

In continuous-time dynamical systems, a periodic orbit becomes a fixed point on a certain Poincaré section. The eigenvalues of the Jacobian matrix at this fixed point determine the local stability of the periodic orbit. Analogously, a quasi-periodic orbit (2-torus) becomes an invariant closed curve (ICC) on a Poincaré section. From the Lyapunov exponents of an ICC, we can determine the time average of the exponential divergence rate of the orbit, which corresponds to the eigenvalues of a fixed point. We denote the Lyapunov exponent with the smallest nonzero absolute value as the Dominant Lyapunov Exponent (DLE). A local bifurcation manifests as a crossing or touch of the DLE locus with zero. However, the type of bifurcation cannot be determined from the DLE. To overcome this problem, we define the Dominant Lyapunov Bundle (DLB), which corresponds to the dominant eigenvectors of a fixed point. We prove that the DLB of a 1-torus in a map can be classified into four types: A+(annulus and orientation preserving), A-(annulus and orientation reversing), M (Möbius band), and F (focus). The DLB of a 2-torus in a flow can be classified into three types: A+× A+, A-× M (equivalently M × A-and M × M), and F × F. From the results, we conjecture the possible local bifurcations in both cases. For the 1-torus in a map, we conjecture that type A+and A-DLBs correspond to a saddle-node and period-doubling bifurcations, respectively, whereas a type M DLB denotes a double-covering bifurcation, and type F relates to a Neimark–Sacker bifurcation. Similarly, for the 2-torus in a flow, we conjecture that type A+× A+DLBs correspond to saddle-node bifurcations, type A-× M DLBs to double-covering bifurcations, and type F × F DLBs to the Neimark–Sacker bifurcations. After introducing the mathematical concepts, we provide a DLB-calculating algorithm and illustrate all of the above bifurcations by examples.
From Fault-Diagnosis and Performance Recovery of a Controlled System to Chaotic Secure Communication
Authors: Hsu Wen-Teng , Tsai Jason Sheng-Hong , Guo Fang-Cheng , Guo Shu-Mei , Shieh Leang-San
Published: January 2015

Chaotic systems are often applied to encryption on secure communication, but they may not provide high-degree security. In order to improve the security of communication, chaotic systems may need to add other secure signals, but this may cause the system to diverge. In this paper, we redesign a communication scheme that could create secure communication with additional secure signals, and the proposed scheme could keep system convergence. First, we introduce the universal state-space adaptive observer-based fault diagnosis/estimator and the high-performance tracker for the sampled-data linear time-varying system with unanticipated decay factors in actuators/system states. Besides, robustness, convergence in the mean, and tracking ability are given in this paper. A residual generation scheme and a mechanism for auto-tuning switched gain is also presented, so that the introduced methodology is applicable for the fault detection and diagnosis (FDD) for actuator and state faults to yield a high tracking performance recovery. The evolutionary programming-based adaptive observer is then applied to the problem of secure communication. Whenever the tracker induces a large control input which might not conform to the input constraint of some physical systems, the proposed modified linear quadratic optimal tracker (LQT) can effectively restrict the control input within the specified constraint interval, under the acceptable tracking performance. The effectiveness of the proposed design methodology is illustrated through tracking control simulation examples.
Stability and Limit Cycle Bifurcation for Two Kinds of Generalized Double Homoclinic Loops in Planar Piecewise Smooth Systems
Authors: Liang Feng , Han Maoan
Published: January 2015

In this paper, we present two kinds of generalized double homoclinic loops in planar piecewise smooth systems. For their stability a criterion is provided. Under nondegenerate conditions, we prove that for each case there are at most five limit cycles which can be bifurcated from the generalized double homoclinic loop. Especially, we construct two concrete systems to show that the upper bound can be achieved in both cases.
Secondary Bifurcations in a Lotka–Volterra Model for N Competitors with Applications to Action Selection and Compulsive Behaviors
Authors: Frank T. D.
Published: January 2015

A Lotka–Volterra model for an arbitrary number of competitors is studied for different ratios of self-inhibition versus cross-inhibition. It is shown that winner-takes-all fixed points (states of single surviving species) are the only stable fixed points of the model when cross-inhibition exceeds self-inhibition. Secondary bifurcations in terms of bifurcations between winner-takes-all fixed points induced by changes in the exponential growth rates of competitors are studied and the critical control parameters are identified. A selection principle is derived that states that evolution proceeds in such a way that exponential growth rates of surviving competitors are magnified in evolutionary bifurcation steps. The interacting competitor model is applied as an amplitude equation model for interacting patterns of self-organizing pattern formation systems with an eye on action selection and compulsive behaviors in humans. The possibility is discussed that human behavior is subjected to the selection principle of "faster growth rates".
Experimental Observations of Propagating Waves and Switching Phenomena in a Coupled Bistable Oscillator System
Authors: Shimizu Kuniyasu
Published: January 2015

In this study, we construct a circuit composed of bistable oscillators and we report the experimental observations of quasi-periodic waves propagating in the circuit and compare them with the associated numerical results. Two different types of propagating quasi-periodic waves with identical parameter sets are experimentally verified. The associated numerical results are distinguished by comparing trajectories on the phase planes and by analyzing the one-parameter bifurcation diagrams. Furthermore, the experiments reveal five different types of switching oscillations. The associated numerical results are also presented, and the stability of the switching oscillations (when constrained to an invariant subspace) is numerically investigated. We also calculate spectral distribution for one type of the switching oscillation.
Period Doubling Motions of a Nonlinear Rotating Beam at 1:1 Resonance
Authors: Wang Fengxia , Qu Yuhui
Published: January 2015

A rotating beam subjected to a torsional excitation is studied in this paper. Both quadratic and cubic geometric stiffening nonlinearities are retained in the equation of motion, and the reduced model is obtained via the Galerkin method. Saddle-node bifurcations and Hopf bifurcations of the period-1 motions of the model were obtained via the higher order harmonic balance method. The period-2 and period-4 solutions, which are emanated from the period-1 and period-2 motions, respectively, are obtained by the combined implementation of the harmonic balance method, Floquet theory, and Discrete Fourier transform (DFT). The analytical periodic solutions and their stabilities are verified through numerical simulation.
Design for a Robotic Companion
Authors: Kędzierski Jan , Kaczmarek Paweł , Dziergwa Michał , Tchoń Krzysztof
Published: January 2015

We can learn from the history of robotics that robots are getting closer to humans, both in the physical as well as in the social sense. The development line of robotics is marked with the triad: industrial — assistive — social robots, that leads from human–robot separation toward human–robot interaction. A social robot is a robot able to act autonomously and to interact with humans using social cues. A social robot that can assist a human for a longer period of time is called a robotic companion. This paper is devoted to the design and control issues of such a robotic companion, with reference to the robot FLASH designed at the Wroclaw University of Technology within the European project LIREC, and currently developed by the authors. Two HRI experiments with FLASH demonstrate the human attitude toward FLASH. A trial testing of the robot's emotional system is described.
Less Talk Is More Play
Authors: Ntina Chrysanthi C. , Ma Xiaohan , Deng Zhigang
Published: January 2015

In this paper, we experimentally study a new type of multiplayer mobile game for casual gamers by introducing the concept of online, team-based strategy forming via visual-only in-game communication. The game is deployed to 12 users, formed as three teams (four players per team), in order to study team-based cooperation and competition that they can develop over time and explore new game design concepts. By analyzing both subjective and objective data collected through online logs, questionnaires, and post-game interviews, we find a number of implications and insights that could be used to guide design of similar types of mobile casual games in the future. In addition, how various gaming elements (e.g., ideal number for team-based game play, user interfaces) can be utilized to design better mobile casual games is also discussed.
GROK-LAB
Authors: Gojman Benjamin , Nalmela Sirisha , Mehta Nikil , Howarth Nicholas , Dehon André
Published: January 2015

Timing Extraction identifies the delay of fine-grained components within an FPGA. From these computed delays, the delay of any path can be calculated. Moreover, a comparison of the fine-grained delays allows a detailed understanding of the amount and type of process variation that exists in the FPGA. To obtain these delays, Timing Extraction measures, using only resources already available in the FPGA, the delay of a small subset of the total paths in the FPGA. We apply Timing Extraction to the Logic Array Block (LAB) on an Altera Cyclone III FPGA to obtain a view of the delay down to near-individual LUT SRAM cell granularity, characterizing components with delays on the order of tens to a few hundred picoseconds with a resolution of ±3.2ps, matching the expected error bounds. This information reveals that the 65nm process used has, on average, random variation of σ μ =4.0% with components having an average maximum spread of 83ps. Timing Extraction also shows that as V

DD

decreases from 1.2V to 0.9V in a Cyclone IV 60nm FPGA, paths slow down, and variation increases from σ μ =4.3% to σ μ =5.8%, a clear indication that lowering V

DD

magnifies the impact of random variation.
Realistic Biomechanical Simulation and Control of Human Swimming
Authors: Si Weiguang , Lee Sung-Hee , Sifakis Eftychios , Terzopoulos Demetri
Published: January 2015

We address the challenging problem of controlling a complex biomechanical model of the human body to synthesize realistic swimming animation. Our human model includes all of the relevant articular bones and muscles, including 103 bones (163 articular degrees of freedom) plus a total of 823 muscle actuators embedded in a finite element model of the musculotendinous soft tissues of the body that produces realistic deformations. To coordinate the numerous muscle actuators in order to produce natural swimming movements, we develop a biomimetically motivated motor control system based on Central Pattern Generators (CPGs), which learns to produce activation signals that drive the numerous muscle actuators.
Mapping Adaptive Particle Filters to Heterogeneous Reconfigurable Systems
Authors: Chau Thomas C. P. , Niu Xinyu , Eele Alison , Maciejowski Jan , Cheung Peter Y. K. , Luk Wayne
Published: January 2015

This article presents an approach for mapping real-time applications based on particle filters (PFs) to heterogeneous reconfigurable systems, which typically consist of multiple FPGAs and CPUs. A method is proposed to adapt the number of particles dynamically and to utilise runtime reconfigurability of FPGAs for reduced power and energy consumption. A data compression scheme is employed to reduce communication overhead between FPGAs and CPUs. A mobile robot localisation and tracking application is developed to illustrate our approach. Experimental results show that the proposed adaptive PF can reduce up to 99% of computation time. Using runtime reconfiguration, we achieve a 25% to 34% reduction in idle power. A 1U system with four FPGAs is up to 169 times faster than a single-core CPU and 41 times faster than a 1U CPU server with 12 cores. It is also estimated to be 3 times faster than a system with four GPUs.
RIMEP2
Authors: Hadjam Fatima Zohra , Moraga Claudio
Published: January 2015

RIMEP (Reversible Improved Multi Expression Programming), is a system that has been developed for designing reversible digital circuits. This article discloses a new version of RIMEP called “RIMEP2”. The goal was to evolve reversible circuits in a “fanout free” search space. The major changes that RIMEP has undergone, are made in the structure of the chromosome and in the fitness calculation. Although the changes seem to be minor, the impact is effective. The execution time has been considerably decreased and optimal competitive solutions were found for a set of 30 selected benchmarks, where a quantum cost reduction up to 96.13% was reached with an average of 42.17%.
Does the internet make us stupid?
Authors: Maurer Hermann
Published: January 2015

Yes, but this may not be as bad as it sounds…
The Complexity of Mining Maximal Frequent Subgraphs
Authors: Kimelfeld Benny , Kolaitis Phokion G.
Published: January 2015

A
frequent subgraph
of a given collection of graphs is a graph that is isomorphic to a subgraph of at least as many graphs in the collection as a given threshold. Frequent subgraphs generalize frequent itemsets and arise in various contexts, from bioinformatics to the Web. Since the space of frequent subgraphs is typically extremely large, research in graph mining has focused on special types of frequent subgraphs that can be orders of magnitude smaller in number, yet encapsulate the space of all frequent subgraphs.
Maximal
frequent subgraphs (i.e., the ones not properly contained in any frequent subgraph) constitute the most useful such type.

In this article, we embark on a comprehensive investigation of the computational complexity of mining maximal frequent subgraphs. Our study is carried out by considering the effect of three different parameters: possible restrictions on the class of graphs; a fixed bound on the threshold; and a fixed bound on the number of desired answers. We focus on specific classes of connected graphs: general graphs, planar graphs, graphs of bounded degree, and graphs of bounded treewidth (trees being a special case). Moreover, each class has two variants: that in which the nodes are unlabeled, and that in which they are uniquely labeled. We delineate the complexity of the enumeration problem for each of these variants by determining when it is solvable in (total or incremental) polynomial time and when it is NP-hard. Specifically, for the labeled classes, we show that bounding the threshold yields tractability but, in most cases, bounding the number of answers does not, unless P=NP; an exception is the case of labeled trees, where bounding either of these two parameters yields tractability. The state of affairs turns out to be quite different for the unlabeled classes. The main (and most challenging to prove) result concerns unlabeled trees: we show NP-hardness, even if the input consists of two trees and both the threshold and the number of desired answers are equal to just two. In other words, we establish that the following problem is NP-complete: given two unlabeled trees, do they have more than one maximal subtree in common?
Wearables
Authors: Rawassizadeh Reza , Price Blaine A. , Petre Marian
Published: January 2015

Time will tell if smartwatches will find their niche.
Efficient Hybrid Inline and Out-of-Line Deduplication for Backup Storage
Authors: Li Yan-Kit , Xu Min , Ng Chun-Ho , Lee Patrick P. C.
Published: January 2015

Backup storage systems often remove redundancy across backups via inline deduplication, which works by referring duplicate chunks of the latest backup to those of existing backups. However, inline deduplication degrades restore performance of the latest backup due to fragmentation, and complicates deletion of expired backups due to the sharing of data chunks. While out-of-line deduplication addresses the problems by forward-pointing existing duplicate chunks to those of the latest backup, it introduces additional I/Os of writing and removing duplicate chunks.

We design and implement
RevDedup
, an efficient hybrid inline and out-of-line deduplication system for backup storage. It applies coarse-grained inline deduplication to remove duplicates of the latest backup, and then fine-grained out-of-line reverse deduplication to remove duplicates from older backups. Our reverse deduplication design limits the I/O overhead and prepares for efficient deletion of expired backups. Through extensive testbed experiments using synthetic and real-world datasets, we show that RevDedup can bring high performance to the backup, restore, and deletion operations, while maintaining high storage efficiency comparable to conventional inline deduplication.
Teaching Introductory Programming
Authors: Koulouri Theodora , Lauria Stanislao , Macredie Robert D.
Published: January 2015

Teaching programming to beginners is a complex task. In this article, the effects of three factors—choice of programming language, problem-solving training, and the use of formative assessment—on learning to program were investigated. The study adopted an iterative methodological approach carried out across 4 consecutive years. To evaluate the effects of each factor (implemented as a single change in each iteration) on students’ learning performance, the study used quantitative, objective metrics. The findings revealed that using a syntactically simple language (Python) instead of a more complex one (Java) facilitated students’ learning of programming concepts. Moreover, teaching problem solving before programming yielded significant improvements in student performance. These two factors were found to have variable effects on the acquisition of basic programming concepts. Finally, it was observed that effective formative feedback in the context of introductory programming depends on multiple parameters. The article discusses the implications of these findings, identifies avenues for further research, and argues for the importance of studies in computer science education anchored on sound research methodologies to produce generalizable results.
Formalizing Modularization and Data Hiding in Synthetic Biology
Authors: Fellermann Harold , Hadorn Maik , Füchslin Rudolf M. , Krasnogor Natalio
Published: January 2015

Biological systems employ compartmentalization and other co-localization strategies in order to orchestrate a multitude of biochemical processes by simultaneously enabling “data hiding” and modularization. This article presents recent research that embraces compartmentalization and co-location as an organizational programmatic principle in synthetic biological and biomimetic systems. In these systems, artificial vesicles and synthetic minimal cells are envisioned as nanoscale reactors for programmable biochemical synthesis and as chassis for molecular information processing. We present P systems, brane calculi, and the recently developed
chemtainer calculus
as formal frameworks providing data hiding and modularization and thus enabling the representation of highly complicated hierarchically organized compartmentalized reaction systems. We demonstrate how compartmentalization can greatly reduce the complexity required to implement computational functionality, and how addressable compartments permit the scaling-up of programmable chemical synthesis.
Did I take my meds today?
Authors: Lee Matthew L.
Published: January 2015

People tend to believe they are more aware of their own health behaviors than they really are. In this article, we present technologies that employ ubiquitous home sensing to support awareness of healthy habits.
A Framework for Dynamic Composition of Communication Services
Authors: Fortuna Carolina , Mohorcic Mihael
Published: January 2015

We propose a framework for dynamic composition of communication services that is well suited for facilitating research and prototyping on real experimental infrastructures of remotely configurable embedded devices. By using the concept of composability, our framework supports modular component development for various networking functions, thereby promoting code reuse. The framework consists of four components: the physical testbed, the module library, the declarative language, and the workbench. Its reference implementation, ProtoStack, developed using semantic web technologies, supports remote experimentation on sensor platform-based infrastructure and is thus well suited also for experimenters who do not possess their own physical experimentation infrastructure. We illustrate how ProtoStack supports research in service-oriented networks and cognitive networking. The cost of increased flexibility and prototyping speed of the protocol stack is paid in terms of increased memory footprint, processing speed, and energy consumption. Compared to the most related noncomposable approach, the CRime library used by ProtoStack has a 16--17% larger footprint, takes 2.4 times longer to execute an open-send-recv-close sequence, and consumes 1.6% more power in doing so. Even though with ProtoStack more resources are consumed by the node, the tradeoff in terms of prototyping speed pays off.
Iterative Training of Dynamic Skills Inspired by Human Coaching Techniques
Authors: Ha Sehoon , Liu C. Karen
Published: January 2015

Inspired by how humans learn dynamic motor skills through a progressive process of coaching and practices, we introduce an intuitive and interactive framework for developing dynamic controllers. The user only needs to provide a primitive initial controller and high-level, human-readable instructions as if s/he is coaching a human trainee, while the character has the ability to interpret the abstract instructions, accumulate the knowledge from the coach, and improve its skill iteratively. We introduce “control rigs” as an intermediate layer of control module to facilitate the mapping between high-level instructions and low-level control variables. Control rigs also utilize the human coach's knowledge to reduce the search space for control optimization. In addition, we develop a new sampling-based optimization method, Covariance Matrix Adaptation with Classification (CMA-C), to efficiently compute-control rig parameters. Based on the observation of human ability to “learn from failure”, CMA-C utilizes the failed simulation trials to approximate an infeasible region in the space of control rig parameters, resulting a faster convergence for the CMA optimization. We demonstrate the design process of complex dynamic controllers using our framework, including precision jumps, turnaround jumps, monkey vaults, drop-and-rolls, and wall-backflips.
When and How to Use Multilevel Modelling
Authors: Lara Juan De , Guerra Esther , Cuadrado Jesús Sánchez
Published: January 2015

Model-Driven Engineering (MDE) promotes models as the primary artefacts in the software development process, from which code for the final application is derived. Standard approaches to MDE (like those based on MOF or EMF) advocate a two-level metamodelling setting where Domain-Specific Modelling Languages (DSMLs) are defined through a metamodel that is instantiated to build models at the metalevel below.

Multilevel modelling
(also called
deep metamodelling
) extends the standard approach to metamodelling by enabling modelling at an arbitrary number of metalevels, not necessarily two. Proposers of multilevel modelling claim this leads to simpler model descriptions in some situations, although its applicability has been scarcely evaluated. Thus, practitioners may find it difficult to discern when to use it and how to implement multilevel solutions in practice.

In this article, we discuss those situations where the use of multilevel modelling is beneficial, and identify recurring patterns and idioms. Moreover, in order to assess how often the identified patterns arise in practice, we have analysed a wide range of existing two-level DSMLs from different sources and domains, to detect when their elements could be rearranged in more than two metalevels. The results show this scenario is not uncommon, while in some application domains (like software architecture and enterprise/process modelling) pervasive, with a high average number of pattern occurrences per metamodel.
In search of Bayesian inference
Authors: Klarreich Erica
Published: January 2015

Long relegated to the statistical backburner, Bayesian Inference is undergoing a renaissance.
Scalability techniques for practical synchronization primitives
Authors: Bueso Davidlohr
Published: January 2015

Designing locking primitives with performance in mind.
How traditional firms must compete in the sharing economy
Authors: Cusumano Michael A.
Published: January 2015

Considering the evolving relationship between established companies and their sharing-economy counterparts.
A right to be forgotten?
Authors: Bygrave Lee A.
Published: January 2015

Searching for an answer to the question of how much responsibility search engine operators should bear for privacy-related issues connected to search engine results.
The tears of Donald Knuth
Authors: Haigh Thomas
Published: January 2015

Has the history of computing taken a tragic turn?
Analyzing worldwide research in hardware architecture, 1997--2011
Authors: Singh Virender , Perdigones Alicia , Garcia José Luis , Cañas-Guerroro Ignacio , Mazarrón Fernando R.
Published: January 2015

Results showed more published papers, collaboration with U.S. colleagues, preference for English, and uneven research impact.
A Scalable Lock Manager for Multicores
Authors: Jung Hyungsoo , Han Hyuck , Fekete Alan , Heiser Gernot , Yeom Heon Y.
Published: January 2015

Modern implementations of DBMS software are intended to take advantage of high core counts that are becoming common in high-end servers. However, we have observed that several database platforms, including MySQL, Shore-MT, and a commercial system, exhibit throughput collapse as load increases into oversaturation (where there are more request threads than cores), even for a workload with little or no logical contention for locks, such as a read-only workload. Our analysis of MySQL identifies latch contention within the lock manager as the bottleneck responsible for this collapse.

We design a lock manager with reduced latching, implement it in MySQL, and show that it avoids the collapse and generally improves performance. Our efficient implementation of a lock manager is enabled by a staged allocation and deallocation of locks. Locks are preallocated in bulk, so that the lock manager only has to perform simple list manipulation operations during the acquire and release phases of a transaction. Deallocation of the lock data structures is also performed in bulk, which enables the use of fast implementations of lock acquisition and release as well as concurrent deadlock checking.
I/O-Efficient Algorithms on Triangle Listing and Counting
Authors: Hu Xiaocheng , Tao Yufei , Chung Chin-Wan
Published: January 2015

This article studies I/O-efficient algorithms for the
triangle listing problem
and the
triangle counting problem
, whose solutions are basic operators in dealing with many other graph problems. In the former problem, given an undirected graph
G
, the objective is to find all the cliques involving 3 vertices in
G
. In the latter problem, the objective is to report just the number of such cliques without having to enumerate them. Both problems have been well studied in internal memory, but still remain as difficult challenges when
G
does not fit in memory, thus making it crucial to minimize the number of disk I/Os performed. Although previous research has attempted to tackle these challenges, the state-of-the-art solutions rely on a set of crippling assumptions to guarantee good performance. Motivated by this, we develop a new algorithm that is provably I/O and CPU efficient at the same time, without making any assumption on the input
G
at all. The algorithm uses ideas drastically different from all the previous approaches, and outperforms the existing competitors by a factor of over an order of magnitude in our extensive experimentation.
Google Boosts ACM's Turing award prize to $1 million
Authors: Fisher Lawrence M.
Published: January 2015

The increase reflects the escalating impact of computing on daily life, through the innovations and technologies it enables.
CLEF 15th Birthday
Authors: Ferro Nicola
Published: January 2015

2014 marks the 15th birthday for CLEF, an evaluation campaign activity which has applied the Cranfield evaluation paradigm to the testing of multilingual and multimodal information access systems in Europe. This paper provides a summary of the motivations which led to the establishment of CLEF, and a description of how it has evolved over the years, the major achievements, and what we see as the next challenges.
ERD'14
Authors: Carmel David , Chang Ming-Wei , Gabrilovich Evgeniy , Hsu Bo-June (Paul) , Wang Kuansan
Published: January 2015

In this paper we overview the 2014 Entity Recognition and Disambiguation Challenge (ERD'14), which took place from March to June 2014 and was summarized in a dedicated workshop at SIGIR 2014. The main goal of the ERD challenge was to promote research in recognition and disambiguation of entities in unstructured text. Unlike many past entity linking challenges, no mention segmentations were given to the participating systems for a given document. Participants were asked to implement a web service for their system to minimize human involvement during evaluation and to enable measuring the processing times. The challenge has attracted a lot of interest (over 100 teams registered, and 27 of those submitted final results).

In this paper we cover the task definition, issues encountered during annotation, and provide a detailed analysis of all the participating systems. Specifically, we show how we adapted the pooling technique to address the difficulties of gathering annotations for the entity linking task. We also summarize the ERD workshop that followed the challenge, including the oral and poster presentations as well as the invited talks.
Fast splittable pseudorandom number generators
Authors: Steele Guy L. , Lea Doug , Flood Christine H.
Published: January 2015

We describe a new algorithm
SplitMix
for an
object-oriented
and
splittable
pseudorandom number generator (PRNG) that is quite fast: 9 64-bit arithmetic/logical operations per 64 bits generated. A conventional linear PRNG object provides a
generate
method that returns one pseudorandom value and updates the state of the PRNG, but a splittable PRNG object also has a second operation,
split
, that replaces the original PRNG object with two (seemingly) independent PRNG objects, by creating and returning a new such object and updating the state of the original object. Splittable PRNG objects make it easy to organize the use of pseudorandom numbers in multithreaded programs structured using fork-join parallelism. No locking or synchronization is required (other than the usual memory fence immediately after object creation). Because the
generate
method has no loops or conditionals, it is suitable for SIMD or GPU implementation.

We derive
SplitMix
from the
DotMix
algorithm of Leiserson, Schardl, and Sukha by making a series of program transformations and engineering improvements. The end result is an object-oriented version of the purely functional API used in the Haskell library for over a decade, but
SplitMix
is faster and produces pseudorandom sequences of higher quality; it is also far superior in quality and speed to java.util.Random, and has been included in Java JDK8 as the class java.util.SplittableRandom.

We have tested the pseudorandom sequences produced by
SplitMix
using two standard statistical test suites (DieHarder and TestU01) and they appear to be adequate for "everyday" use, such as in Monte Carlo algorithms and randomized data structures where speed is important.
Late data layout
Authors: Ureche Vlad , Burmako Eugene , Odersky Martin
Published: January 2015

Values need to be represented differently when interacting with certain language features. For example, an integer has to take an object-based representation when interacting with erased generics, although, for performance reasons, the stack-based value representation is better. To abstract over these implementation details, some programming languages choose to expose a unified high-level concept (the integer) and let the compiler choose its exact representation and insert coercions where necessary.

This pattern appears in multiple language features such as value classes, specialization and multi-stage programming: they all expose a unified concept which they later refine into multiple representations. Yet, the underlying compiler implementations typically entangle the core mechanism with assumptions about the alternative representations and their interaction with other language features.

In this paper we present the Late Data Layout mechanism, a simple but versatile type-driven generalization that subsumes and improves the state-of-the-art representation transformations. In doing so, we make two key observations: (1) annotated types conveniently capture the semantics of using multiple representations and (2) local type inference can be used to consistently and optimally introduce coercions.

We validated our approach by implementing three language features as Scala compiler extensions: value classes, specialization (using the miniboxing representation) and a simplified multi-stage programming mechanism.