bluuebunny/crossref_metadata_2025 huggingface dataset:
MAGNETIC FIELD ALIGNMENT OF BARIUM FERRITE THICK FILMS FOR MICROWAVE CIRCULATOR APPLICATIONS
Authors: PENG BIN , WANG YUANCHAO , ZHANG WANLI , ZHANG WENXU , TAN KE
Published: September 2012

Barium ferrite films were prepared using screen printing method for their applications in self-biased microwave integrated circulators. The influences of alignment magnetic field on the microstructure and magnetic properties of the barium ferrite thick films were investigated. The results show that the (00l) peaks of the barium ferrite films are enhanced with the increase of alignment magnetic field. Hexagonal BaFe 12 O 19 platelets rotate and orient with c-axis perpendicular to the film plane after the magnetic field aligning. The remanence ratio of the barium ferrite films is improved from 0.52 to 0.78 with the increase of alignment magnetic field from 0 to 8 kOe. By magnetic field aligning, barium ferrite thick films with the remanence ratio of 0.8 have been prepared. A prototype of microwave integrated circulator is developed with the prepared barium ferrite films.
INVESTIGATION OF THE PHOTOLUMINESCENCE PROPERTIES OF ZnSe and ZnSe:Cu NANAOCRYSTALS (NCs)
Authors: ORAEE N. , MOLAEI M. , IRANIZAD E. SAIEVAR
Published: September 2012

In this work, ZnSe and ZnSe : Cu nanocrystals (NCs) were synthesized using a simple aqueous thermochemical approach. XRD pattern demonstrated cubic structure (zinc blende) of ZnSe NCs with an average size around 2.5 nm. The band gap of as-prepared ZnSe NCs was about 3.5 eV and by increasing the heating time the band gap of NCs was decreased. The PL spectra of as-prepared ZnSe NCs showed trap state emission, but by increasing the heating time, it indicated the band edge emission. For ZnSe : Cu NCs, the PL peak was shifted from 470 nm to 565 nm by increasing the heating time.
DO ABSENCE DATA MATTER WHEN MODELLING FISH HABITAT PREFERENCE USING A GENETIC TAKAGI-SUGENO FUZZY MODEL?
Authors: FUKUDA SHINJI , DE BAETS BERNARD
Published: September 2012

Information on species distributions is of key importance when designing management plans for a target species or ecosystem. This paper illustrates the effects of absence data on fish habitat prediction and habitat preference evaluation using a genetic Takagi-Sugeno fuzzy model. Three independent data sets were prepared from a series of fish habitat surveys conducted in an agricultural canal in Japan. To quantify the effects of absence data, two kinds of abundance data (entire data and presence data) were used for developing a fuzzy habitat preference model (FHPM). As a result, habitat preference curves (HPCs) obtained from presence data resulted in similar HPCs between the three data sets, while those obtained from entire data slightly differed according to the data sets. The higher generalization ability of the FHPMs obtained from presence data supports the usefulness of presence data for better extracting the habitat preference information of a target species from field observation data.
STEREODYNAMICS STUDY OF THE ABSTRACTION REACTION H + CD4 → HD + CD3
Authors: CHENG DAHAI , YANG TIANGANG , CHEN MAODU
Published: September 2012

A new London–Eyring–Polanyi–Sato (LEPS) potential energy surface (PES) is employed in this work to study the stereo properties for the abstraction reaction of hydrogen with methane at its rovibrationally ground state using the quasiclassical trajectory method (QCT). A "quasi-triatomic" approximation is used to treat the CD3 group of CD4 as a pseudoatom. The calculated excitation function of the title reaction can give a good agreement to most experimental and theoretical data at collision energies (Ec =1.5 ~ 2.5 eV ). Further investigation of the product HD in reaction H + CD4 (v = 0, j = 0) → HD + CD3 and D + CH4 (v = 0, j = 0) → HD + CH3 shows the dependence of the product rotational polarization on collision energies and mass factor, but P(θr) is not sensitive to both the collision energies and the mass factor.
Fault linkage and damage zone architecture in tight carbonate rocks in the Suez Rift (Egypt): implications for permeability structure along segmented normal faults
Authors: Rotevatn A. , Bastesen E.
Published: September 2012

A field study focusing on fracture systems in a fault linkage zone from the Suez Rift, Egypt, is presented to elucidate the role of fault linkage zones in the permeability structure of segmented normal faults in tight carbonate rocks. Fracture systems in the linking damage zone show significantly increased structural complexity compared to that typical of isolated faults. The linkage zone is characterized by high fracture frequencies and multiple fracture sets of different orientations. Notably, pervasive fracture corridors strike at high angles to the fault trend and are interpreted to have formed during the latest evolutionary stages of what is interpreted as a breached relay. The structural observations indicate that along segmented normal faults in carbonate rocks, fault linkage zones represents locations of progressively increased cross- and along-fault permeability through the stages of relay growth and breaching. Our findings, in combination with previously published work, indicate that fault linkage zones represent localized conduits not only for increased fluid flow across faults, but also (vertically) within fault zones. Appreciating this has wide-ranging implications for understanding fluid transport in carbonate rocks and other naturally fractured lithologies.
The importance of natural fractures in a tight reservoir for potential CO
2
storage: a case study of the upper Triassic–middle Jurassic Kapp Toscana Group (Spitsbergen, Arctic Norway)
Authors: Ogata K. , Senger K. , Braathen A. , Tveranger J. , Olaussen S.
Published: September 2012

In the Longyearbyen CO
2
laboratory project, it is planned to inject carbon dioxide into a Triassic–Jurassic fractured sandstone–shale succession (Kapp Toscana Group) at a depth of 700–1000 m below the local settlement. The targeted storage sandstones offer moderate secondary porosity and low permeability (unconventional reservoir), whereas water injection tests evidence good lateral fluid flow facilitated by extensive fracturing. Therefore, a detailed investigation of fracture sets/discontinuities and their characteristics have been undertaken, concentrating on the upper reservoir interval (670–706 m). Datasets include drill cores and well logs, and observations of outcrops, that mainly show fracturing but also some disaggregation deformation bands in the sandstones. The fracture distribution has a lithostratigraphical relationship, and can be subdivided into: (A) massive to laminated shaly intervals, offering abundant lower-angle shear fractures; (B) massive to thin-bedded, heterogeneous, mixed silty–shaly intervals, with a predominance of non-systematic, pervasive bed-confined fractures; and (C) massive to laminated, medium- to thick-bedded, fine- to coarse-grained sandstones with a lower frequency of mostly steep fractures. These domains represent pseudo-geomechanical units characterized by specific fracture sets and fracture intensity, with indicated relationships between the bed thickness and fracture intensity, and with domains separated along bedding interfaces. We discuss the impact of these lithostructural domains on the fluid flow pathways in the heterolithic storage unit.
A theory of monte carlo visibility sampling
Authors: Ramamoorthi Ravi , Anderson John , Meyer Mark , Nowrouzezahrai Derek
Published: September 2012

Soft shadows from area lights are one of the most crucial effects in high-quality and production rendering, but Monte-Carlo sampling of visibility is often the main source of noise in rendered images. Indeed, it is common to use deterministic uniform sampling for the smoother shading effects in direct lighting, so that all of the Monte Carlo noise arises from visibility sampling alone. In this article, we analyze theoretically and empirically, using both statistical and Fourier methods, the effectiveness of different nonadaptive Monte Carlo sampling patterns for rendering soft shadows.

We start with a single image scanline and a linear light source, and gradually consider more complex visibility functions at a pixel. We show analytically that the lowest expected variance is in fact achieved by uniform sampling (albeit at the cost of visual banding artifacts). Surprisingly, we show that for two or more discontinuities in the visibility function, a comparable error to uniform sampling is obtained by “uniform jitter” sampling, where a constant jitter is applied to all samples in a uniform pattern (as opposed to jittering each stratum as in standard stratified sampling). The variance can be reduced by up to a factor of two, compared to stratified or quasi-Monte Carlo techniques, without the banding in uniform sampling.

We augment our statistical analysis with a novel 2D Fourier analysis across the pixel-light space. This allows us to characterize the banding frequencies in uniform sampling, and gives insights into the behavior of uniform jitter and stratified sampling. We next extend these results to planar area light sources. We show that the best sampling method can vary, depending on the type of light source (circular, Gaussian, or square/rectangular). The correlation of adjacent “light scanlines” in square light sources can reduce the effectiveness of uniform jitter sampling, while the smoother shape of circular and Gaussian-modulated sources preserves its benefits—these findings are also exposed through our frequency analysis. In practical terms, the theory in this article provides guidelines for selecting visibility sampling strategies, which can reduce the number of shadow samples by 20--40%, with simple modifications to existing rendering code.
Reflectance model for diffraction
Authors: Cuypers Tom , Haber Tom , Bekaert Philippe , Oh Se Baek , Raskar Ramesh
Published: September 2012

We present a novel method of simulating wave effects in graphics using ray-based renderers with a new function: the Wave BSDF (Bidirectional Scattering Distribution Function). Reflections from neighboring surface patches represented by local BSDFs are mutually independent. However, in many surfaces with wavelength-scale microstructures, interference and diffraction requires a joint analysis of reflected wavefronts from neighboring patches. We demonstrate a simple method to compute the BSDF for the entire microstructure, which can be used independently for each patch. This allows us to use traditional ray-based rendering pipelines to synthesize wave effects. We exploit the Wigner Distribution Function (WDF) to create transmissive, reflective, and emissive BSDFs for various diffraction phenomena in a physically accurate way. In contrast to previous methods for computing interference, we circumvent the need to explicitly keep track of the phase of the wave by using BSDFs that include positive as well as negative coefficients. We describe and compare the theory in relation to well-understood concepts in rendering and demonstrate a straightforward implementation. In conjunction with standard raytracers, such as PBRT, we demonstrate wave effects for a range of scenarios such as multibounce diffraction materials, holograms, and reflection of high-frequency surfaces.
Video stabilization using epipolar geometry
Authors: Goldstein Amit , Fattal Raanan
Published: September 2012

We present a new video stabilization technique that uses projective scene reconstruction to treat jittered video sequences. Unlike methods that recover the full three-dimensional geometry of the scene, this model accounts for simple geometric relations between points and epipolar lines. Using this level of scene understanding, we obtain the physical correctness of 3D stabilization methods yet avoid their lack of robustness and computational costs. Our method consists of tracking feature points in the scene and using them to compute fundamental matrices that model stabilized camera motion. We then project the tracked points onto the novel stabilized frames using epipolar point transfer and synthesize new frames using image-based frame warping. Since this model is only valid for static scenes, we develop a time-view reprojection that accounts for nonstationary points in a principled way. This reprojection is based on modeling the dynamics of smooth inertial object motion in three-dimensional space and allows us to avoid the need to interpolate stabilization for moving objects from their static surrounding. Thus, we achieve an adequate stabilization when both the camera and the objects are moving. We demonstrate the abilities of our approach to stabilize hand-held video shots in various scenarios: scenes with no parallax that challenge 3D approaches, scenes containing nontrivial parallax effects, videos with camera zooming and in-camera stabilization, as well as movies with large moving objects.
More is more
Authors: Johnson Matthew P. , Sariöz Deniz , Bar-Noy Amotz , Brown Theodore , Verma Dinesh , Wu Chai W.
Published: September 2012

Positioning disk-shaped sensors to optimize certain coverage parameters is a fundamental problem in ad hoc sensor networks. The hexagon lattice arrangement is known to be optimally efficient in the plane, even though 20.9% of the area is unnecessarily covered twice, however, the arrangement is very rigid—any movement of a sensor from its designated grid position (due to, e.g., placement error or obstacle avoidance) leaves some region uncovered, as would the failure of any one sensor. In this article, we consider how to arrange sensors in order to guarantee multiple coverage, that is,
k
-coverage for some value
k
> 1. A naive approach is to superimpose multiple hexagon lattices, but for robustness reasons, we may wish to space sensors evenly apart.

We present two arrangement methods for
k
-coverage: (1) optimizing a Riesz energy function in order to evenly distribute nodes, and (2) simply shrinking the hexagon lattice and making it denser. The first method often approximates the second, and so we focus on the latter. We show that a density increase tantamount to
k
copies of the lattice can yield
k
′-coverage, for
k
′ >
k
(e.g.,
k
= 11,
k
′ = 12 and
k
= 21,
k
′ = 24), by exploiting the double-coverage regions. Our examples' savings provably converge in the limit to the ≈ 20.9% maximum. We also provide analogous results for the square lattice and its ≈ 57% inefficiency (e.g.,
k
= 3,
k
′ = 4 and
k
=5,
k
′ = 7) and show that for multi-coverage for some values of
k
′, the square lattice can actually be more efficient than the hexagon lattice.

We also explore other benefits of shrinking the lattice: Doing so allows all sensors to move about their intended positions independently while nonetheless guaranteeing full coverage and can also allow us to tolerate probabilistic sensor failure when providing 1-coverage or
k
-coverage. We conclude by construing the shrinking factor as a budget to be divided among these three benefits.
Sensor activation and radius adaptation (SARA) in heterogeneous sensor networks
Authors: Bartolini Novella , Calamoneri Tiziana , La Porta Tom , Petrioli Chiara , Silvestri Simone
Published: September 2012

In order to prolong the lifetime of a wireless sensor network (WSN) devoted to monitoring an area of interest, a useful means is to exploit network redundancy, activating only the sensors that are strictly necessary for coverage and making them work with the minimum necessary sensing radius.

In this article, we introduce the first algorithm that reduces sensor coverage redundancy through joint Sensor Activation and sensing Radius Adaptation (SARA) in general application scenarios comprising two classes of devices: sensors with variable sensing radius and sensors with fixed sensing radius. This device heterogeneity is explicitly addressed by modeling the coverage problem through Voronoi-Laguerre diagrams that, differently from Voronoi diagrams, allow for correctly identifying each sensor coverage region depending on the sensor current radius and the radii of its neighboring nodes. SARA executes quickly with guaranteed termination and, given the currently available nodes, it always guarantees maximum coverage. By means of extensive simulations, we show that SARA obtains remarkable improvements with respect to previous solutions, ensuring, in networks with heterogeneous nodes, longer network lifetime and wider coverage.
Coverage estimation for crowded targets in visual sensor networks
Authors: Karakaya Mahmut , Qi Hairong
Published: September 2012

Coverage estimation is one of the fundamental problems in sensor networks. Coverage estimation in visual sensor networks (VSNs) is more challenging than in conventional 1-D (omnidirectional) scalar sensor networks (SSNs) because of the directional sensing nature of cameras and the existence of visual occlusion in crowded environments. This article represents a first attempt toward a closed-form solution for the visual coverage estimation problem in the presence of occlusions. We investigate a new target detection model, referred to as the
certainty-based target detection
(as compared to the traditional
uncertainty-based target detection
) to facilitate the formulation of the visual coverage problem. We then derive the closed-form solution for the estimation of the visual coverage probability based on this new target detection model that takes visual occlusions into account. According to the coverage estimation model, we further propose an estimate of the minimum sensor density that suffices to ensure a visual K-coverage in a crowded sensing field. Simulation is conducted which shows extreme consistency with results from theoretical formulation, especially when the boundary effect is considered. Thus, the closed-form solution for visual coverage estimation is effective when applied to real scenarios, such as efficient sensor deployment and optimal sleep scheduling.
Localized policy-based target tracking using wireless sensor networks
Authors: Misra Sudip , Singh Sweta
Published: September 2012

Wireless Sensor Networks (WSN)-based surveillance applications necessitate tracking a target's trajectory with a high degree of precision. Further, target tracking schemes should consider energy consumption in these resource-constrained networks. In this work, we propose an energy-efficient target tracking algorithm, which minimizes the number of nodes in the network that should be activated for tracking the movement of the target. We model the movement of a target based on the Gauss Markov Mobility Model [Camp et al. 2002]. On detecting a target, the cluster head which detects it activates an optimal number of nodes within its cluster, so that these nodes start sensing the target. A Markov Decision Process (MDP)-based framework is designed to adaptively determine the optimal policy for selecting the nodes localized with each cluster. As the distance between the node and the target decreases, the Received Signal Strength (RSS) increases, thereby increasing the precision of the readings of sensing the target at each node. Simulations show that our proposed algorithm is energy-efficient. Also, the accuracy of the tracked trajectory varies between 50% to 1% over time.
Parallel Reconfigurable Computing-Based Mapping Algorithm for Motion Estimation in Advanced Video Coding
Authors: Paul Anand , Jiang Yung-Chuan , Wang Jhing-Fa , Yang Jar-Ferr
Published: September 2012

Computational load of motion estimation in advanced video coding (AVC) standard is significantly high and even worse for HDTV and super-resolution sequences. In this article, a video processing algorithm is dynamically mapped onto a new parallel reconfigurable computing (PRC) architecture which consists of multiple dynamic reconfigurable computing (DRC) units. First, we construct a directed acyclic graph (DAG) to represent video coding algorithms in which motion estimation is the focus. A novel parallel partition approach is then proposed to map motion estimation DAG onto the multiple DRC units in a PRC system. This partitioning algorithm is capable of design optimization of parallel processing reconfigurable systems for a given number of processing elements in different search ranges. This speeds up the video processing with minimum sacrifice.
BAND-AiDe
Authors: Banerjee Ayan , Kandula Sailesh , Mukherjee Tridib , Gupta Sandeep K. S.
Published: September 2012

Body area networks (BANs) are networks of medical devices implanted within or worn on the human body. Analysis and verification of BAN designs require (i) early feedback on the BAN design and (ii) high-confidence evaluation of BANs without requiring any hazardous, intrusive, and costly deployment. Any design of BAN further has to ensure (i) the safety of the human body, that is, limiting any undesirable side-effects (e.g., heat dissipation) of BAN operations (involving sensing, computation, and communication among the devices) on the human body, and (ii) the sustainability of the BAN operations, that is, the continuation of the operations under constrained resources (e.g., limited battery power in the devices) without requiring any redeployments. This article uses the Model Based Engineering (MBE) approach to perform design and analysis of BANs. In this regard, first, an abstract cyber-physical model of BANs, called BAN-CPS, is proposed that captures the undesirable side-effects of the medical devices (cyber) on the human body (physical); second, a design and analysis tool, named BAND-AiDe, is developed that allows specification of BAN-CPS using industry standard Abstract Architecture Description Language (AADL) and enables safety and sustainability analysis of BANs; and third, the applicability of BAND-AiDe is shown through a case study using both single and a network of medical devices for health monitoring applications.
Impact of Wireless Channel Temporal Variation on MAC Design for Body Area Networks
Authors: Boulis Athanassios , Tselishchev Yuriy , Libman Lavy , Smith David , Hanlen Leif
Published: September 2012

We investigate the impact of wireless channel temporal variations on the design of medium access control (MAC) protocols for body area networks (BANs). Our measurements-based channel model captures large and small time-scale signal correlations, giving an accurate picture of the signal variation, specifically, the deep fades which are the features that mostly affect the behavior of the MAC. We test the effect of the channel model on the performance of the 802.15.4 MAC both in contention access mode and TDMA access mode. We show that there are considerable differences in the performance of the MAC compared to simulations that do not model channel temporal variation. Furthermore, explaining the behavior of the MAC under a temporal varying channel, we can suggest specific design choices for the emerging BAN MAC standard.
Verification of Periodically Controlled Hybrid Systems
Authors: Wongpiromsarn Tichakorn , Mitra Sayan , Lamperski Andrew , Murray Richard M.
Published: September 2012

This article introduces Periodically Controlled Hybrid Automata (PCHA) for modular specification of embedded control systems. In a PCHA,
control
actions that change the control input to the plant occur roughly periodically, while other actions that update the state of the controller may occur in the interim. Such actions could model, for example, sensor updates and information received from higher-level planning modules that change the set point of the controller. Based on periodicity and subtangential conditions, a new sufficient condition for verifying invariant properties of PCHAs is presented. For PCHAs with polynomial continuous vector fields, it is possible to check these conditions automatically using, for example, quantifier elimination or sum of squares decomposition. We examine the feasibility of this automatic approach on a small example. The proposed technique is also used to manually verify safety and progress properties of a fairly complex planner-controller subsystem of an autonomous ground vehicle. Geometric properties of planner-generated paths are derived which guarantee that such paths can be safely followed by the controller.
A Model Checking Based Approach to Bounding Worst-Case Execution Time for Multicore Processors
Authors: Wu Lan , Zhang Wei
Published: September 2012

As multicore processors are increasingly adopted in industry, it has become a great challenge to accurately bound the worst-case execution time (WCET) for real-time systems running on multicore chips. This is particularly true because of the inter-thread interferences in accessing shared resources on multicores, such as shared L2 caches, which can significantly affect the performance but are very difficult to be estimated statically.

This article proposes an approach to analyzing WCET for multicore processors with shared L2 instruction caches by using a model checking based method. We model each concurrent real-time thread, including the inter-thread cache interferences with a PROMELA process, and derive the WCET by using a binary search algorithm. To reduce the state explosion problem, we propose several techniques for reducing the memory consumption by exploiting domain-specific information. Our experiments indicate that compared to the static analysis technique based on extended ILP (integer linear programming), our approach improves the tightness of WCET estimation by more than 31.1% for the benchmarks we studied. However, due to the inherent complexity of multicore timing analysis and the state explosion problem, the model checking based approach currently can only work with small real-time kernels for dual-core processors.
A Unified Methodology for Scheduling in Distributed Cyber-Physical Systems
Authors: Tang Qinghui , Gupta Sandeep K. S. , Varsamopoulos Georgios
Published: September 2012

A distributed cyber-physical system (DCPS) may receive and induce energy-based interference to and from its environment. This article presents a model and an associated methodology that can be used to (i) schedule tasks in DCPSs to ensure that the thermal effects of the task execution are within acceptable levels, and (ii) verify that a given schedule meets the constraints. The model uses coarse discretization of space and linearity of interference. The methodology involves characterizing the interference of the task execution and fitting it into the model, then using the fitted model to verify a solution or explore the solution space.
Ontology learning from text
Authors: Wong Wilson , Liu Wei , Bennamoun Mohammed
Published: September 2012

Ontologies are often viewed as the answer to the need for interoperable semantics in modern information systems. The explosion of textual information on the Read/Write Web coupled with the increasing demand for ontologies to power the Semantic Web have made (semi-)automatic ontology learning from text a very promising research area. This together with the advanced state in related areas, such as natural language processing, have fueled research into ontology learning over the past decade. This survey looks at how far we have come since the turn of the millennium and discusses the remaining challenges that will define the research directions in this area in the near future.
HPSG-Based Preprocessing for English-to-Japanese Translation
Authors: Isozaki Hideki , Sudoh Katsuhito , Tsukada Hajime , Duh Kevin
Published: September 2012

Japanese sentences have completely different word orders from corresponding English sentences. Typical phrase-based statistical machine translation (SMT) systems such as Moses search for the best word permutation within a given distance limit (distortion limit). For English-to-Japanese translation, we need a large distance limit to obtain acceptable translations, and the number of translation candidates is extremely large. Therefore, SMT systems often fail to find acceptable translations within a limited time. To solve this problem, some researchers use rule-based preprocessing approaches, which reorder English words just like Japanese by using dozens of rules. Our idea is based on the following two observations: (1) Japanese is a typical head-final language, and (2) we can detect heads of English sentences by a head-driven phrase structure grammar (HPSG) parser. The main contributions of this article are twofold: First, we demonstrate how off-the-shelf, state-of-the-art HPSG parser enables us to write the reordering rules in an abstract level and can easily improve the quality of English-to-Japanese translation. Second, we also show that syntactic heads achieve better results than semantic heads. The proposed method outperforms the best system of NTCIR-7 PATMT EJ task.
Adaptive Bayesian HMM for Fully Unsupervised Chinese Part-of-Speech Induction
Authors: Zhang Lidan , Chan Kwop-Ping
Published: September 2012

We propose an adaptive Bayesian hidden Markov model for fully unsupervised part-of-speech (POS) induction. The proposed model with its inference algorithm has two extensions to the first-order Bayesian HMM with Dirichlet priors. First our algorithm infers the optimal number of hidden states from the training corpus rather than fixes the dimensionality of state space beforehand. The second extension studies the Chinese unknown word processing module which measures similarities from both morphological properties and context distribution. Experimental results showed that both of these two extensions can help to find the optimal categories for Chinese in terms of both unsupervised clustering metrics and grammar induction accuracies on the Chinese Treebank.
Revisiting answering tree pattern queries using views
Authors: Wang Junhu , Xu Yu Jeffrey
Published: September 2012

We revisit the problem of answering tree pattern queries using views. We first show that, for queries and views that do not have nodes labeled with the wildcard *, there is an approach which does not require us to find any rewritings explicitly, yet which produces the same answers as the maximal contained rewriting. Then, using the new approach, we give simple conditions and a corresponding algorithm for identifying redundant view answers, which are view answers that can be ignored when evaluating the maximal contained rewriting. We also consider redundant view answers in the case where there are multiple views, the relationship between redundant views and redundant view answers, and discuss how to combine the removal of redundant view answers and redundant rewritings. We show that the aforesaid results can be extended to a number of other special cases. Finally, for arbitrary queries and views in
P
{/,//,.,[]}
, we provide a method to find the maximal contained rewriting and show how to answer the query using views without explicitly finding the rewritings.
Reordering rows for better compression
Authors: Lemire Daniel , Kaser Owen , Gutarra Eduardo
Published: September 2012

Sorting database tables before compressing them improves the compression rate. Can we do better than the lexicographical order? For minimizing the number of runs in a run-length encoding compression scheme, the best approaches to row-ordering are derived from traveling salesman heuristics, although there is a significant trade-off between running time and compression. A new heuristic, Multiple Lists, which is a variant on Nearest Neighbor that trades off compression for a major running-time speedup, is a good option for very large tables. However, for some compression schemes, it is more important to generate long runs rather than few runs. For this case, another novel heuristic, Vortex, is promising. We find that we can improve run-length encoding up to a factor of 3 whereas we can improve prefix coding by up to 80%: these gains are on top of the gains due to lexicographically sorting the table. We prove that the new row reordering is optimal (within 10%) at minimizing the runs of identical values within columns, in a few cases.
Technical debt in software development
Authors: Kruchten Philippe , Nord Robert L. , Ozkaya Ipek , Visser Joost
Published: September 2012

The technical debt metaphor is gaining significant traction in the software development community as a way to understand and communicate issues of intrinsic quality, value, and cost. This is a report on a third workshop on managing technical debt, which took place as part of the 34rd International Conference on Software Engineering (ICSE 2012). The goal of this third workshop was to discuss managing technical debt as a part of the research agenda for the software engineering field, in particular focusing on eliciting and visualizing debt, and creating payback strategies.
Optimizing feature-access time through dynamic updates to application menu layout
Authors: Jain Ajay
Published: September 2012

As soon as a product or application is installed, users want to start using it with zero usability roadblocks. However, there is always a time quantity associated with a user's series of actions that must be performed while traversing application menu items to reach a specific (desired) menu option. This time factor plays a critical role in influencing user experience and engagement; the more the number of clicks, the greater the time taken in reaching the desired menu item. This time lag may leave the user frustrated. The
time and distance traversed increases
further if the menu structure comprises multiple nested menus within the parent menu.

This paper proposes an improvised dynamic menu layout based on usage statistics. This work also demonstrates results of a statistical experiment that compares the time taken in reaching specific menu items with the proposed new layout vs. the traditional menu layout. Experimental data (under defined assumptions) is found to be significantly in favor of the proposed approach. The work also presents data samples, assumptions, limitations, and benefits of the proposed approach.
A note on rigour and replicability
Authors: Louridas Panos , Gousios Georgios
Published: September 2012

As any empirical science, Software Engineering research should strive towards better research practices. Replication is regrettably not a priority for Software Engineering researchers and, moreover, not afforded by many published studies. Here we report our experience from our encounter with a recent paper in a agship Software Engineering conference. Our experience shows that current publication requirements do not guarantee replicability.
A survey in the area of machine learning and its application for software quality prediction
Authors: Rashid Ekbal , Patnayak Srikanta , Bhattacherjee Vandana
Published: September 2012

This paper explores software quality improvement through early prediction of error patterns. It summarizes a variety of techniques for software quality prediction in the domain of software engineering. The objective of this research is to apply the various machine learning approaches, such as Case-Based Reasoning and Fuzzy logic, to predict software quality. The system predicts the error after accepting the values of certain parameters of the software. This paper advocates the use of case-based reasoning (i.e., CBR) to build a software quality prediction system with the help of human experts. The prediction is based on analogy. We have used different similarity measures to find the best method that increases reliability. This software is compiled using Turbo C++ 3.0 and hence it is very compact and standalone. It can be readily deployed on any configuration without affecting its performance.
libdft
Authors: Kemerlis Vasileios P. , Portokalidis Georgios , Jee Kangkook , Keromytis Angelos D.
Published: September 2012

Dynamic data flow tracking (DFT) deals with tagging and tracking data of interest as they propagate during program execution. DFT has been repeatedly implemented by a variety of tools for numerous purposes, including protection from zero-day and cross-site scripting attacks, detection and prevention of information leaks, and for the analysis of legitimate and malicious software. We present libdft, a dynamic DFT framework that unlike previous work is at once fast, reusable, and works with commodity software and hardware. libdft provides an API for building DFT-enabled tools that work on unmodified binaries, running on common operating systems and hardware, thus facilitating research and rapid prototyping. We explore different approaches for implementing the low-level aspects of instruction-level data tracking, introduce a more efficient and 64-bit capable shadow memory, and identify (and avoid) the common pitfalls responsible for the excessive performance overhead of previous studies. We evaluate libdft using real applications with large codebases like the Apache and MySQL servers, and the Firefox web browser. We also use a series of benchmarks and utilities to compare libdft with similar systems. Our results indicate that it performs at least as fast, if not faster, than previous solutions, and to the best of our knowledge, we are the first to evaluate the performance overhead of a fast dynamic DFT implementation in such depth. Finally, libdft is freely available as open source software.
Execution mining
Authors: Lefebvre Geoffrey , Cully Brendan , Head Christopher , Spear Mark , Hutchinson Norm , Feeley Mike , Warfield Andrew
Published: September 2012

Operating systems represent large pieces of complex software that are carefully tested and broadly deployed. Despite this, developers frequently have little more than their source code to understand how they behave. This static representation of a system results in limited insight into execution dynamics, such as what code is important, how data flows through a system, or how threads interact with one another. We describe Tralfamadore, a system that preserves complete traces of machine execution as an artifact that can be queried and analyzed with a library of simple, reusable operators, making it easy to develop and run new dynamic analyses. We demonstrate the benefits of this approach with several example applications, including a novel unified source and execution browser.
Replacement attacks against VM-protected applications
Authors: Ghosh Sudeep , Hiser Jason , Davidson Jack W.
Published: September 2012

Process-level virtualization is increasingly being used to enhance the security of software applications from reverse engineering and unauthorized modification (called software protection). Process-level virtual machines (PVMs) can safeguard the application code at run time and hamper the adversary's ability to launch dynamic attacks on the application. This dynamic protection, combined with its flexibility, ease in handling legacy systems and low performance overhead, has made process-level virtualization a popular approach for providing software protection. While there has been much research on using process-level virtualization to provide such protection, there has been less research on attacks against PVM-protected software. In this paper, we describe an attack on applications protected using process-level virtualization, called a replacement attack. In a replacement attack, the adversary replaces the protecting PVM with an attack VM thereby rendering the application vulnerable to analysis and modification. We present a general description of the replacement attack methodology and two attack implementations against a protected application using freely available tools. The generality and simplicity of replacement attacks demonstrates that there is a strong need to develop techniques that meld applications more tightly to the protecting PVM to prevent such attacks.
V2E
Authors: Yan Lok-Kwong , Jayachandra Manjukumar , Zhang Mu , Yin Heng
Published: September 2012

A transparent and extensible malware analysis platform is essential for defeating malware. This platform should be transparent so malware cannot easily detect and bypass it. It should also be extensible to provide strong support for heavyweight instrumentation and analysis efficiency. However, no existing platform can meet both requirements. Leveraging hardware virtualization technology, analysis platforms like Ether can achieve good transparency, but its instrumentation support and analysis efficiency is poor. In contrast, software emulation provides strong support for code instrumentation and good analysis efficiency by using dynamic binary translation. However, analysis platforms based on software emulation can be easily detected by malware and thus is poor in transparency. To achieve both transparency and extensibility, we propose a new analysis platform that combines hardware virtualization and software emulation. The essence is precise heterogeneous replay: the malware execution is recorded via hardware virtualization and then replayed in software. Our design ensures the execution replay is precise. Moreover, with page-level recording granularity, the platform can easily adjust to analyze various forms of malware (a process, a kernel module, or a shared library). We implemented a prototype called V2E and demonstrated its capability and efficiency by conducting an extensive evaluation with both synthetic samples and 14 realworld emulation-resistant malware samples.
RAIDR
Authors: Liu Jamie , Jaiyen Ben , Veras Richard , Mutlu Onur
Published: September 2012

Dynamic random-access memory (DRAM) is the building block of modern main memory systems. DRAM cells must be periodically refreshed to prevent loss of data. These refresh operations waste energy and degrade system performance by interfering with memory accesses. The negative effects of DRAM refresh increase as DRAM device capacity increases. Existing DRAM devices refresh all cells at a rate determined by the leakiest cell in the device. However, most DRAM cells can retain data for significantly longer. Therefore, many of these refreshes are unnecessary.

In this paper, we propose RAIDR (Retention-Aware Intelligent DRAM Refresh), a low-cost mechanism that can identify and skip unnecessary refreshes using knowledge of cell retention times. Our key idea is to group DRAM rows into retention time bins and apply a different refresh rate to each bin. As a result, rows containing leaky cells are refreshed as frequently as normal, while most rows are refreshed less frequently. RAIDR uses Bloom filters to efficiently implement retention time bins. RAIDR requires no modification to DRAM and minimal modification to the memory controller. In an 8-core system with 32 GB DRAM, RAIDR achieves a 74.6% refresh reduction, an average DRAM power reduction of 16.1%, and an average system performance improvement of 8.6% over existing systems, at a modest storage overhead of 1.25 KB in the memory controller. RAIDR's benefits are robust to variation in DRAM system configuration, and increase as memory capacity increases.
PARDIS
Authors: Bojnordi Mahdi Nazm , Ipek Engin
Published: September 2012

Modern memory controllers employ sophisticated address mapping, command scheduling, and power management optimizations to alleviate the adverse effects of DRAM timing and resource constraints on system performance. A promising way of improving the versatility and efficiency of these controllers is to make them programmable---a proven technique that has seen wide use in other control tasks ranging from DMA scheduling to NAND Flash and directory control. Unfortunately, the stringent latency and throughput requirements of modern DDRx devices have rendered such programmability largely impractical, confining DDRx controllers to fixed-function hardware.

This paper presents the instruction set architecture (ISA) and hardware implementation of PARDIS, a programmable memory controller that can meet the performance requirements of a high-speed DDRx interface. The proposed controller is evaluated by mapping previously proposed DRAM scheduling, address mapping, refresh scheduling, and power management algorithms onto PARDIS. Simulation results show that the average performance of PARDIS comes within 8% of fixed-function hardware for each of these techniques; moreover, by enabling application-specific optimizations, PARDIS improves system performance by 6--17% and reduces DRAM energy by 9--22% over four existing memory controllers.
BOOM
Authors: Yoon Doe Hyun , Chang Jichuan , Muralimanohar Naveen , Ranganathan Parthasarathy
Published: September 2012

To address the real-time processing needs of large and growing amounts of data, modern software increasingly uses main memory as the primary data store for critical information. This trend creates a new emphasis on high-capacity, high-bandwidth, and high-reliability main memory systems. Conventional and recently-proposed server memory techniques can satisfy these requirements, but at the cost of significantly increased memory power, a key constraint for future memory systems. In this paper, we exploit the low-power nature of another high volume memory component---mobile DRAM---while improving its bandwidth and reliability shortcomings with a new DIMM architecture. We propose Buffered Output On Module (BOOM) that buffers the data outputs from multiple ranks of low-frequency mobile DRAM devices, which in aggregation provide high bandwidth and achieve chipkill-correct or even stronger reliability. Our evaluation shws that BOOM can reduce main memory power by more than 73% relative to the baseline chipkill system, while improving average performance by 5% and providing strong reliability. For memory-intensive applications, BOOM can improve performance by 30--40%.
Towards energy-proportional datacenter memory with mobile DRAM
Authors: Malladi Krishna T. , Lee Benjamin C. , Nothaft Frank A. , Kozyrakis Christos , Periyathambi Karthika , Horowitz Mark
Published: September 2012

To increase datacenter energy efficiency, we need memory systems that keep pace with processor efficiency gains. Currently, servers use DDR3 memory, which is designed for high bandwidth but not for energy proportionality. A system using 20% of the peak DDR3 bandwidth consumes 2.3x the energy per bit compared to the energy consumed by a system with fully utilized memory bandwidth. Nevertheless, many datacenter applications stress memory capacity and latency but not memory bandwidth. In response, we architect server memory systems using mobile DRAM devices, trading peak bandwidth for lower energy consumption per bit and more efficient idle modes. We demonstrate 3-5x lower memory power, better proportionality, and negligible performance penalties for datacenter workloads.
Boosting mobile GPU performance with a decoupled access/execute fragment processor
Authors: Arnau José-María , Parcerisa Joan-Manuel , Xekalakis Polychronis
Published: September 2012

Smartphones represent one of the fastest growing markets, providing significant hardware/software improvements every few months. However, supporting these capabilities reduces the operating time per battery charge. The CPU/GPU component is only left with a shrinking fraction of the power budget, since most of the energy is consumed by the screen and the antenna.

In this paper, we focus on improving the energy efficiency of the GPU since graphical applications consist an important part of the existing market. Moreover, the trend towards better screens will inevitably lead to a higher demand for improved graphics rendering. We show that the main bottleneck for these applications is the texture cache and that traditional techniques for hiding memory latency (prefetching, multithreading) do not work well or come at a high energy cost.

We thus propose the migration of GPU designs towards the decoupled access-execute concept. Furthermore, we significantly reduce bandwidth usage in the decoupled architecture by exploiting inter-core data sharing. Using commercial Android applications, we show that the end design can achieve 93% of the performance of a heavily multithreaded GPU while providing energy savings of 34%.