bluuebunny/crossref_metadata_2025 huggingface dataset:
An Improved Sparse Representation over Learned Dictionary Method for Seizure Detection
Authors: Li Junhui , Zhou Weidong , Yuan Shasha , Zhang Yanli , Li Chengcheng , Wu Qi
Published: September 2015

Automatic seizure detection has played an important role in the monitoring, diagnosis and treatment of epilepsy. In this paper, a patient specific method is proposed for seizure detection in the long-term intracranial electroencephalogram (EEG) recordings. This seizure detection method is based on sparse representation with online dictionary learning and elastic net constraint. The online learned dictionary could sparsely represent the testing samples more accurately, and the elastic net constraint which combines the 11-norm and 12-norm not only makes the coefficients sparse but also avoids over-fitting problem. First, the EEG signals are preprocessed using wavelet filtering and differential filtering, and the kernel function is applied to make the samples closer to linearly separable. Then the dictionaries of seizure and nonseizure are respectively learned from original ictal and interictal training samples with online dictionary optimization algorithm to compose the training dictionary. After that, the test samples are sparsely coded over the learned dictionary and the residuals associated with ictal and interictal sub-dictionary are calculated, respectively. Eventually, the test samples are classified as two distinct categories, seizure or nonseizure, by comparing the reconstructed residuals. The average segment-based sensitivity of 95.45%, specificity of 99.08%, and event-based sensitivity of 94.44% with false detection rate of 0.23/h and average latency of -5.14 s have been achieved with our proposed method.
IMPACT OF PLASMA SURFACE TREATMENT ON BAMBOO CHARCOAL/SILVER NANOCOMPOSITE
Authors: VIGNESH K. , VIJAYALAKSHMI K. A. , KARTHIKEYAN N.
Published: September 2015

Bamboo charcoal (BC) accompanied silver (Ag) nanocomposite is synthesized through sol–gel method. The produced BC/Ag nanocomposite was surface modified by air and oxygen plasma treatments. Silver ions (Ag[Formula: see text]) will serve to improve the antibacterial activity as well as the surface area of BC. Plasma treatment has improved the surface functional groups, crystalline intensity and antibacterial activity of the prepared nanocomposite. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) studies show that Ag nanoparticles have good agreement with BC and the particle size has a mean diameter of 20–40[Formula: see text]nm. We observe the carboxyl functional groups in Fourier transform infrared spectroscopy (FTIR) after the oxygen plasma treatment. Moreover surface area and adsorption were analyzed by using the Brunauer, Emmett and Teller (BET) surface area ([Formula: see text]) and UV–Vis spectroscopy.
Differences of Opinion and Price Reversals: Evidence from the Taiwan Stock Exchange
Authors: Cheng Chu-Chun , Huang Yen-Sheng
Published: September 2015

This paper examines the impact of differences of opinion (DIFOPN) on long-term price reversals using all of the common stocks listed on the Taiwan Stock Exchange over the period of 1990–2008. We choose winners and losers ranked by their cumulative abnormal returns (CARs) over the three-year formation period. The performance of the winners and losers is evaluated over the subsequent one-year holding periods. The empirical results indicate that DIFOPN are generally positively related to price reversals in the holding period for both winners and losers. When DIFOPN are measured by the financial analysts' forecasts of earnings per share and by the standard deviation of stock returns, the association between DIFOPN and price reversals is significantly different from zero. This relationship is robust when such control variables as market-to-book ratios, size, and beta are included.
On the generalized local cohomology of minimax modules
Authors: Roshan-Shekalgourabi H. , Hassanzadeh-Lelekaami D.
Published: September 2015

Let [Formula: see text] be a commutative Noetherian ring with identity and [Formula: see text] be an ideal of [Formula: see text]. Assume that [Formula: see text] is a finite [Formula: see text]-module and [Formula: see text] and [Formula: see text] are minimax [Formula: see text]-modules such that [Formula: see text]. In this paper, among other things, we show that [Formula: see text] is minimax for all [Formula: see text] and [Formula: see text] when one of the following conditions holds: [Formula: see text](i) [Formula: see text]; [Formula: see text] (ii) [Formula: see text]; or (iii) [Formula: see text].

As a consequence, we obtain that the Bass numbers and Betti numbers of [Formula: see text] are finite for all [Formula: see text] when one of the above conditions holds.
THE “WIN-CONTINUE, LOSE-REVERSE” RULE IN OLIGOPOLIES: ROBUSTNESS OF COLLUSIVE OUTCOMES
Authors: IZQUIERDO SEGISMUNDO S. , IZQUIERDO LUIS R.
Published: September 2015

The so-called “Win-Continue, Lose-Reverse” (WCLR) rule is a simple iterative procedure that can be used to choose a value for any numeric variable (e.g., setting a price or a production level). The rule dictates that one should evaluate the effect on profits of the last adjustment made to the value (e.g., a price variation), and keep on changing the value in the same direction if the adjustment led to greater profits, or reverse the direction of change otherwise. Somewhat surprisingly, this simple rule has been shown to lead to collusive outcomes in Cournot oligopolies, even though its application requires no information about the other firms’ profits or choices. In this paper, we show that the convergence of the WCLR rule toward collusive outcomes can be very sensitive to small independent perturbations in the cost functions or in the income functions of the firms. These perturbations typically push the process toward the Nash equilibrium of the one-shot game. We also explore the behavior of WCLR against other strategies and demonstrate that WCLR is easily exploitable. We then conduct a similar analysis of the WCLR rule in a differentiated Bertrand model, where firms compete in prices.
PCA-Based Algorithms to Find Synergies for Humanoid Robot Motion Behavior
Authors: Tripathi Gyanendra Nath , Wagatsuma Hiroaki
Published: September 2015

Applying principal component analysis (PCA) to find synergy signal for specific motion of Robot is a standard method. However, implementation of PCA gives synergy solely on quantitative basis. The algorithms proposed in this paper advocates the enhancement of qualitative measure of PCA to locate well-coordinated synergy signals. The two main control strategies of central nervous system (CNS) are taken into account for enhancement of algorithms. First one is the CNS strategy of separate synergy generation for individual limbs and second is the trajectory generation of complex movement using via-points. The proposed algorithms find the synergy without loss of generality of implementation. Humanoid robot NAO is used as a robotic platform to test the result of the algorithm. The synergy for a group of motors is calculated by implementing the algorithm on motors position sensor data of the robot corresponding to three motion pattern 1. Knee bend sitting–standing, 2. Sitting–standing on chair, and 3. Walking. The improvement in result is statistically measured by calculating error between original and reconstructed signal for proposed algorithms and applying Z-test tested on error signals. Another statistical measure of improvement is treated by calculating ‘Goodness of Fit’ for original and reconstructed signal.
Effect of GPU Communication-Hiding for SPMV Using OpenACC
Authors: Fagerlund Olav Aanes , Kitayama Takeshi , Hashimoto Gaku , Okuda Hiroshi
Published: September 2015

In this study, we discuss overlapping possibilities of Sparse Matrix-Vector multiplication (SpMV) in cases where we have multiple RHS-vectors and where the whole sparse matrix data may or may not fit into the memory of the discrete GPU, at once, by using OpenACC. With GPUs, one can take advantage of their relatively high memory bandwidths. However, data needs to be transferred over the relatively slow PCIe bus. We implement communication-hiding to increase performance.

In the case of three degrees of freedom and modeling 2,097,152 nodes, we observe a just above 40% performance increase by applying communication-hiding in our routine. This underlines the importance of applying such techniques in simulations, when it is suitable with the algorithmic structure of the problem in relation to the underlying computer architecture.
Convolutional Neural Networks with Fused Layers Applied to Face Recognition
Authors: Syafeeza A. R. , Khalil-Hani M. , Liew S. S. , Bakhteri R.
Published: September 2015

In this paper, we propose an effective convolutional neural network (CNN) model to the problem of face recognition. The proposed CNN architecture applies fused convolution/subsampling layers that result in a simpler model with fewer network parameters; that is, a smaller number of neurons, trainable parameters, and connections. In addition, it does not require any complex or costly image preprocessing steps that are typical in existing face recognizer systems. In this work, we enhance the stochastic diagonal Levenberg–Marquardt algorithm, a second-order back-propagation algorithm to obtain faster network convergence and better generalization ability. Experimental work completed on the ORL database shows that a recognition accuracy of 100% is achieved, with the network converging within 15 epochs. The average processing time of the proposed CNN face recognition solution, executed on a 2.5 GHz Intel i5 quad-core processor, is 3 s per epoch, with a recognition speed of less than 0.003 s. These results show that the proposed CNN model is a computationally efficient architecture that exhibits faster processing and learning times, and also produces higher recognition accuracy, outperforming other existing work on face recognizers based on neural networks.
Bernoulli and poly-Bernoulli polynomial convolutions and identities of p-adic Arakawa–Kaneko zeta functions
Authors: Young Paul Thomas
Published: September 2015

We evaluate the ordinary convolution of Bernoulli polynomials in closed form in terms of poly-Bernoulli polynomials. As applications we derive identities for [Formula: see text]-adic Arakawa–Kaneko zeta functions, including a [Formula: see text]-adic analogue of Ohno’s sum formula. These [Formula: see text]-adic identities serve to illustrate the relationships between real periods and their [Formula: see text]-adic analogues.
The (u,v)-Calkin–Wilf forest
Authors: Han Sandie , Masuda Ariane M. , Singh Satyanand , Thiel Johann
Published: September 2015

In this paper, we consider a refinement, due to Nathanson, of the Calkin–Wilf tree. In particular, we study the properties of such trees associated with the matrices [Formula: see text] and [Formula: see text], where [Formula: see text] and [Formula: see text] are non-negative integers. We extend several known results of the original Calkin–Wilf tree, including the symmetry, numerator-denominator, and successor formulas, to this new setting. Additionally, we study the ancestry of a rational number appearing in a generalized Calkin–Wilf tree.
Synthesis of Carbon-Coated LiFePO4Cathode Material by One-Step Microwave-Assisted Pyrolysis of Ionic Liquid Process
Authors: Meng Yanshuang , Zhang Zhong , Han Wangqing , Zhang Yue , Zhu Fuliang , Wang Dajian
Published: September 2015

A one-step microwave-assisted pyrolysis of ionic liquid process is developed to synthesize carbon-coated LiFePO4by using the ionic liquid [BMIm]N(CN)2as a carbon source. A thin layer of uniform and nanoscaled carbon film is formed on the LiFePO4particles surface with a strong interface. The electrochemical properties of LiFePO4are improved due to the carbon coating which increases the electronic conductivity of LiFePO4. The results indicate that the microwave-assisted pyrolysis of ionic liquid process is a rapid and efficient method to prepare carbon-coated LiFePO4material and other carbon-coated electrode materials.
Synthesis of TiO2/rGO Nanocomposites with Enhanced Photoelectrochemical Performance and Photocatalytic Activity
Authors: Kong Dewang , Zhao Min , Li Shikuo , Huang Fangzhi , Song Jiming , Yuan Yupeng , Shen Yuhua , Xie Anjian
Published: September 2015

In this paper, a facile and efficient method combined sol–gel method with hydrothermal process was employed for preparing titanium dioxide (TiO[Formula: see text]/reduced graphene oxide (rGO) nanocomposites without using any reductants or surfactants. This approach leads to the reduction of graphene oxide (GO) and the growth of TiO2 nanorods simultaneously. The results reveal that the TiO2 short nanorods with average size of 15[Formula: see text]nm in length and 10[Formula: see text]nm in diameter were uniformly grown on the rGO sheets with high dispersion. Compared with the pure TiO2 nanoparticles, the TiO2/rGO composites exhibit strong absorption in the visible light range. The photocurrent density of nanocomposites reached 0.826[Formula: see text]mA/cm2 under the simulated sunlight illumination, which is 3.5 times than that of pure TiO2. An enhancement of photocatalytic hydrogen formation rate for the water splitting was observed over the TiO2/rGO composite photocatalysts, the fastest formation rate can reach 889.28[Formula: see text][Formula: see text]mol[Formula: see text]g[Formula: see text]h[Formula: see text] when TiO2 coupling with 1wt.% rGO. Also the hydrogen production rate is about 3.27 times larger than pure TiO2 and 2.23 times than P25 due to the excellent electron trapping and transportation properties of rGO and the synergistic effect between TiO2 and rGO.
Helly and exchange numbers of geodesic and Steiner convexities in lexicographic product of graphs
Authors: Anand Bijo S. , Changat Manoj , Narasimha-Shenoi Prasanth G.
Published: September 2015

We discuss the convexity invariants, namely, the exchange and Helly numbers of the Steiner and geodesic convexity in lexicographic product of graphs. We use the structure of both the Steiner and geodesic convex sets in the lexicographic product for proving the results. Along the way the exchange number of the induced path convexity in arbitrary graphs is also determined.
Delegating Computation
Authors: Goldwasser Shafi , Kalai Yael Tauman , Rothblum Guy N.
Published: September 2015

In this work we study interactive proofs for tractable languages. The (honest) prover should be efficient and run in polynomial time or, in other words, a “muggle”.1 The verifier should be super-efficient and run in nearly linear time. These proof systems can be used for delegating computation: a server can run a computation for a client and interactively prove the correctness of the result. The client can verify the result’s correctness in nearly linear time (instead of running the entire computation itself).

Previously, related questions were considered in the holographic proof setting by Babai et al. [1991b] in the argument setting under computational assumptions by Kilian, and in the random oracle model by Micali [1994]. Our focus, however, is on the original interactive proof model where no assumptions are made on the computational power or adaptiveness of dishonest provers.

Our main technical theorem gives a public coin interactive proof for any language computable by a log-space uniform boolean circuit with depth
d
and input length
n
. The verifier runs in time n · poly(
d
, log(
n
)) and space
O
(log(
n
)), the communication complexity is poly(
d
, log(
n
)), and the prover runs in time poly(
n
). In particular, for languages computable by log-space uniform
NC
(circuits of polylog(
n
) depth), the prover is efficient, the verifier runs in time
n
· polylog(
n
) and space
O
(log(
n
)), and the communication complexity is polylog(
n
). Using this theorem we make progress on several questions.

--- We show how to construct 1-round computationally sound arguments with polylog communication for any log-space uniform
NC
computation. The verifier runs in quasi-linear time. This result uses a recent transformation of Kalai and Raz from public coin interactive
proofs
to 1-round
arguments
. The soundness of the argument system is based on the existence of a PIR scheme with polylog communication.

--- We construct interactive proofs with public coin, log-space, poly-time verifiers for all of
P
are given. This settles an open question regarding the expressive power of proof systems with such verifiers.

--- We construct zero-knowledge interactive proofs are given with communication complexity quasi-linear in the
witness
length for any
NP
language verifiable in
NC
, based on the existence of 1-way functions.

--- We construct probabilistically checkable arguments (a model due to Kalai and Raz) of size polynomial in the witness length (rather than instance length) for any
NP
language verifiable in
NC
, under computational assumptions, are provided.
Algorithmic Applications of Baur-Strassen’s Theorem
Authors: Cygan Marek , Gabow Harold N. , Sankowski Piotr
Published: September 2015

Consider a directed or an undirected graph with integral edge weights from the set [-W, W], that does not contain negative weight cycles. In this article, we introduce a general framework for solving problems on such graphs using matrix multiplication. The framework is based on the usage of Baur-Strassen’s theorem and of Strojohann’s determinant algorithm. It allows us to give new and simple solutions to the following problems:

Finding Shortest Cycles
. We give a simple
Õ
(
Wnω
) time algorithm for finding shortest cycles in undirected and directed graphs. For directed graphs (and undirected graphs with nonnegative weights), this matches the time bounds obtained in 2011 by Roditty and Williams. On the other hand, no algorithm working in
Õ
(
Wn ω
) time was previously known for undirected graphs with negative weights. Furthermore, our algorithm for a given directed or undirected graph detects whether it contains a negative weight cycle within the same running time.

Computing Diameter and Radius
. We give a simple
Õ
(
Wnω
) time algorithm for computing a diameter and radius of an undirected or directed graphs. To the best of our knowledge, no algorithm with this running time was known for undirected graphs with negative weights.

Finding Minimum-Weight Perfect Matchings
. We present an
Õ
(
Wnω
) time algorithm for finding minimum-weight perfect matchings in undirected graphs. This resolves an open problem posted by Sankowski [2009] who presented such an algorithm but only in the case of bipartite graphs.

These three problems that are solved in the full generality demonstrate the utility of this framework. Hence, we believe that it can find applications for solving larger spectra of related problems. As an illustrative example, we apply it to the problem of computing a set of vertices that lie on cycles of length at most
t
, for some given
t
. We give a simple
Õ
(
Wnω
) time algorithm for this problem that improves over the
Õ
(
Wnωt
) time algorithm given by Yuster in 2011.

Besides giving this flexible framework, the other main contribution of this article is the development of a novel combinatorial interpretation of the dual solution for the minimum-weight perfect matching problem. Despite the long history of the matching problem, such a combinatorial interpretation was not known previously. This result sheds a new light on the problem, as there exist many structural theorems about unweighted matchings, but almost no results that could cope with the weighted case.
Interactive Visuals as Metaphors for Dance Movement Qualities
Authors: Alaoui Sarah Fdili , Bevilacqua Frederic , Jacquemin Christian
Published: September 2015

The notion of “movement qualities” is central in contemporary dance; it describes the manner in which a movement is executed. Movement qualities convey information revealing movement expressiveness; their use has strong potential for movement-based interaction with applications in arts, entertainment, education, or rehabilitation. The purpose of our research is to design and evaluate interactive reflexive visuals for movement qualities. The theoretical basis for this research is drawn from a collaboration with the members of the international dance company Emio Greco|PC to study their formalization of movement qualities. We designed a pedagogical interactive installation called
Double Skin/Double Mind (DS/DM)
for the analysis and visualization of movement qualities through physical model-based interactive renderings.

In this article, we first evaluate dancers’ perception of the visuals as metaphors for movement qualities. This evaluation shows that, depending on the physical model parameterization, the visuals are capable of generating dynamic behaviors that the dancers associate with
DS/DM
movement qualities. Moreover, we evaluate dance students’ and professionals’ experience of the interactive visuals in the context of a dance pedagogical workshop and a professional dance training. The results of these evaluations show that the dancers consider the interactive visuals to be a reflexive system that encourages them to perform, improves their experience, and contributes to a better understanding of movement qualities. Our findings support research on interactive systems for real-time analysis and visualization of movement qualities, which open new perspectives in movement-based interaction design.
Quantitative Study of Music Listening Behavior in a Smartphone Context
Authors: Yang Yi-Hsuan , Teng Yuan-Ching
Published: September 2015

Context-based services have attracted increasing attention because of the prevalence of sensor-rich mobile devices such as smartphones. The idea is to recommend information that a user would be interested in according to the user’s surrounding context. Although remarkable progress has been made to contextualize music playback, relatively little research has been made using a large collection of real-life listening records collected
in situ
. In light of this fact, we present in this article a quantitative study of the personal, situational, and musical factors of musical preference in a smartphone context, using a new dataset comprising the listening records and self-report context annotation of 48 participants collected over 3wk via an Android app. Although the number of participants is limited and the population is biased towards students, the dataset is unique in that it is collected in a daily context, with sensor data and music listening profiles recorded at the same time. We investigate 3 core research questions evaluating the strength of a rich set of low-level and high-level audio features for music usage auto-tagging (i.e., music preference in different user activities), the strength of time-domain and frequency-domain sensor features for user activity classification, and how user factors such as personality traits are correlated with the predictability of music usage and user activity, using a closed set of 8 activity classes. We provide an in-depth discussion of the main findings of this study and their implications for the development of context-based music services for smartphones.
SuperDragon
Authors: Tan Guangming , Zhang Chunming , Wang Wendi , Zhang Peiheng
Published: September 2015

The data deluge in medical imaging processing requires faster and more efficient systems. Due to the advance in recent heterogeneous architecture, there has been a resurgence in research aimed at domain-specific accelerators. In this article, we develop an experimental system SuperDragon for evaluating acceleration of a single-particle Cryo-electron microscopy (Cryo-EM) 3D reconstruction package
EMAN
through a hybrid of CPU, GPU, and FPGA parallel architecture. Based on a comprehensive workload characterization, we exploit multigrained parallelism in the Cryo-EM 3D reconstruction algorithm and investigate a proper computational mapping to the underlying heterogeneous architecture. The package is restructured with task-level (MPI), thread-level (OpenMP), and data-level (GPU and FPGA) parallelism. Especially, the proposed FPGA accelerator is a stream architecture that emphasizes the importance of optimizing computing dominated data access patterns. Besides, the configurable computing streams are constructed by arranging the hardware modules and bypassing channels to form a linear deep pipeline. Compared to the multicore (six-core) program, the GPU and FPGA implementations achieve speedups of 8.4 and 2.25 times in execution time while improving power efficiency by factors of 7.2 and 14.2, respectively.
Failure Semantics for Modal Transition Systems
Authors: Bujtor Ferenc , Vogler Walter
Published: September 2015

With the aim to preserve deadlock freedom, we define a new refinement preorder for modal transition systems (MTSs), using an MTS-specific variant of testing inspired by De Nicola and Hennessy. We characterize this refinement with a kind of failure semantics and show that it “supports itself,” for example, in the sense of thoroughness—in contrast to standard modal refinements. We present a conjunction operator with respect to our new refinement, which is quite different from existing ones. It always returns an MTS—again in contrast to the case of modal refinement. Finally, we also consider De Nicola’s and Hennessy’s may- and must-testing, where the latter leads to a semantics that is also compositional for hiding.
Action Synthesis for Branching Time Logic
Authors: Knapik Michał , Męski Artur , Penczek Wojciech
Published: September 2015

The article introduces a parametric extension of Action-Restricted Computation Tree Logic called pmARCTL. A symbolic fixed-point algorithm providing a solution to the exhaustive parameter synthesis problem is proposed. The parametric approach allows for an in-depth system analysis and synthesis of the correct parameter values. The time complexity of the problem and the algorithm is provided. An existential fragment of pmARCTL (pmEARCTL) is identified, in which all of the solutions can be generated from a minimal and unique base. A method for computing this base using symbolic methods is provided. The prototype tool SPATULA implementing the algorithm is applied to the analysis of three benchmarks: faulty Train-Gate-Controller, Peterson’s mutual exclusion protocol, and a generic pipeline processing network. The experimental results show efficiency and scalability of our approach compared to the naive solution to the problem.
Robust Satisfiability of Systems of Equations
Authors: Franek Peter , Krčál Marek
Published: September 2015

We study the problem of
robust satisfiability
of systems of nonlinear equations, namely, whether for a given continuous function
f
:
K
→ Rn on a finite simplicial complex
K
and α>0, it holds that each function
g
:
K
→ Rn such that ║
g−f
║∞ ≤
α
, has a root in
K
. Via a reduction to the extension problem of maps into a sphere, we particularly show that this problem is decidable in polynomial time for every fixed
n
, assuming dim
K
≤ 2
n
−3. This is a substantial extension of previous computational applications of
topological degree
and related concepts in numerical and interval analysis.

Via a reverse reduction, we prove that the problem is undecidable when dim
K
≥ 2
n
−2, where the threshold comes from the
stable range
in homotopy theory.

For the lucidity of our exposition, we focus on the setting when
f
is simplexwise linear. Such functions can approximate general continuous functions, and thus we get approximation schemes and undecidability of the robust satisfiability in other possible settings.
Architecture-Aware Real-Time Compression of Execution Traces
Authors: Mihajlović Bojan , Žilić Željko , Gross Warren J.
Published: September 2015

In recent years, on-chip trace generation has been recognized as a solution to the debugging of increasingly complex software. An
execution trace
can be seen as the most fundamentally useful type of trace, allowing the execution path of software to be determined post hoc. However, the bandwidth required to output such a trace can be excessive. Our architecture-aware trace compression (AATC) scheme adds an on-chip branch predictor and branch target buffer to reduce the volume of execution trace data in real time through on-chip compression. Novel redundancy reduction strategies are employed, most notably in exploiting the widespread use of
linked branches
and the compiler-driven movement of return addresses between link register, stack, and program counter. In doing so, the volume of
branch target addresses
is reduced by 52%, whereas other algorithmic improvements further decrease trace volume. An analysis of spatial and temporal redundancy in the trace stream allows a comparison of encoding strategies to be made for systematically increasing compression performance. A combination of differential, Fibonacci, VarLen, and Move-to-Front encodings are chosen to produce two compressor variants: a performance-focused xAATC that encodes 56.5 instructions/bit using 24,133 gates and an area-efficient fAATC that encodes 48.1 instructions/bit using only 9,854 gates.
Upper Bounds for Newton’s Method on Monotone Polynomial Systems, and P-Time Model Checking of Probabilistic One-Counter Automata
Authors: Stewart Alistair , Etessami Kousha , Yannakakis Mihalis
Published: September 2015

A central computational problem for analyzing and model checking various classes of infinite-state recursive probabilistic systems (including quasi-birth-death processes, multitype branching processes, stochastic context-free grammars, probabilistic pushdown automata and recursive Markov chains) is the computation of termination probabilities, and computing these probabilities in turn boils down to computing the least fixed point (LFP) solution of a corresponding monotone polynomial system (MPS) of equations, denoted
x
=
P
(
x
).

It was shown in Etessami and Yannakakis [2009] that a decomposed variant of Newton’s method converges monotonically to the LFP solution for any MPS that has a nonnegative solution. Subsequently, Esparza et al. [2010] obtained upper bounds on the convergence rate of Newton’s method for certain classes of MPSs. More recently, better upper bounds have been obtained for special classes of MPSs [Etessami et al. 2010, 2012].

However, prior to this article, for arbitrary (not necessarily strongly connected) MPSs, no upper bounds at all were known on the convergence rate of Newton’s method as a function of the encoding size |P| of the input MPS,
x
=
P
(
x
).

In this article, we provide worst-case upper bounds, as a function of both the input encoding size |P|, and
ε
> 0, on the number of iterations required for decomposed Newton’s method (even with rounding) to converge to within additive error
ε
> 0 of q*, for an arbitrary MPS with LFP solution q*. Our upper bounds are essentially optimal in terms of several important parameters of the problem.

Using our upper bounds, and building on prior work, we obtain the first P-time algorithm (in the standard Turing model of computation) for quantitative model checking, to within arbitrary desired precision, of discrete-time QBDs and (equivalently) probabilistic 1-counter automata, with respect to any (fixed)
ω
-regular or LTL property.
Memory Interface Design for 3D Stencil Kernels on a Massively Parallel Memory System
Authors: Jin Zheming , Bakos Jason D.
Published: September 2015

Massively parallel memory systems are designed to deliver high bandwidth at relatively low clock speed for memory-intensive applications implemented on programmable logic. For example, the Convey HC-1 provides 1,024 DRAM banks to each of four FPGAs through a full crossbar, presenting a peak bandwidth of 76.8GB/s to the user logic. Such highly parallel memory systems suffer from high latency, and their effective bandwidth is highly sensitive to access ordering. To achieve high performance, the user must use a customized memory interface that combines scheduling, latency hiding, and data reuse. In this article, we describe the design of a custom memory interface for 3D stencil kernels on the Convey HC-1 that incorporates these features. Experimental results show that the proposed memory interface achieves a speedup in runtime of 2.2 for 6-point stencil and 9.5 for 27-point stencil when compared to a naive memory interface.
SybilCast
Authors: Gilbert Seth , Zheng Chaodong
Published: September 2015

Consider a scenario where many wireless users are attempting to download data from a single base station. While most of the users are honest, some users may be malicious and attempt to obtain more than their fair share of the bandwidth. One possible strategy for attacking the system is to simulate multiple fake identities, each of which is given its own equal share of the bandwidth. Such an attack is often referred to as a
sybil attack
. To counter such behavior, we propose
SybilCast
, a protocol for multichannel wireless networks that limits the number of fake identities and, in doing so, ensures that each honest user gets at least a constant fraction of his or her fair share of the bandwidth. As a result, each honest user can complete his or her data download in asymptotically optimal time. A key aspect of this protocol is balancing the rate at which new identities are admitted and the maximum number of fake identities that can coexist while keeping the overhead low. Besides sybil attacks, our protocol can also tolerate spoofing and jamming.
Fast Greedy Algorithms in MapReduce and Streaming
Authors: Kumar Ravi , Moseley Benjamin , Vassilvitskii Sergei , Vattani Andrea
Published: September 2015

Greedy algorithms are practitioners’ best friends—they are intuitive, are simple to implement, and often lead to very good solutions. However, implementing greedy algorithms in a distributed setting is challenging since the greedy choice is inherently sequential, and it is not clear how to take advantage of the extra processing power.

Our main result is a powerful sampling technique that aids in parallelization of sequential algorithms. Armed with this primitive, we then adapt a broad class of greedy algorithms to the MapReduce paradigm; this class includes maximum cover and submodular maximization subject to
p
-system constraint problems. Our method yields efficient algorithms that run in a logarithmic number of rounds while obtaining solutions that are arbitrarily close to those produced by the standard sequential greedy algorithm. We begin with algorithms for modular maximization subject to a matroid constraint and then extend this approach to obtain approximation algorithms for submodular maximization subject to knapsack or
p
-system constraints.
Profitable Scheduling on Multiple Speed-Scalable Processors
Authors: Kling Peter , Pietrzyk Peter
Published: September 2015

We present a new online algorithm for profit-oriented scheduling on multiple speed-scalable processors and provide a tight analysis of the algorithm’s competitiveness. Our results generalize and improve upon work by Chan et al. [2010], which considers a single speed-scalable processor. Using significantly different techniques, we can not only extend their model to multiprocessors but also prove an enhanced and tight competitive ratio for our algorithm.

In our scheduling problem, jobs arrive over time and are preemptable. They have different workloads, values, and deadlines. The scheduler may decide not to finish a job but instead to suffer a loss equaling the job’s value. However, to process a job’s workload until its deadline the scheduler must invest a certain amount of energy. The cost of a schedule is the sum of lost values and invested energy. In order to finish a job, the scheduler has to determine which processors to use and set their speeds accordingly. A processor’s energy consumption is power P
α
(
s
) integrated over time, where P
α
(
s
)=
s
α
is the power consumption when running at speed
s
. Since we consider the online variant of the problem, the scheduler has no knowledge about future jobs. This problem was introduced by Chan et al. [2010] for the case of a single processor. They presented an online algorithm that is α
α
+ 2
e
α-competitive. We provide an online algorithm for the case of multiple processors with an improved competitive ratio of α
α
.
Big Foot
Authors: Jun Eunice , Stefanucci Jeanine K. , Creem-Regehr Sarah H. , Geuss Michael N. , Thompson William B.
Published: September 2015

Spatial perception research in the real world and in virtual environments suggests that the body (e.g., hands) plays a role in the perception of the scale of the world. However, little research has closely examined how varying the size of virtual body parts may influence judgments of action capabilities and spatial layout. Here, we questioned whether changing the size of virtual feet would affect judgments of stepping over and estimates of the width of a gap. Participants viewed their disembodied virtual feet as small or large and judged both their ability to step over a gap and the size of gaps shown in the virtual world. Foot size affected both affordance judgments and size estimates such that those with enlarged virtual feet estimated they could step over larger gaps and that the extent of the gap was smaller. Shrunken feet led to the perception of a reduced ability to step over a gap and smaller estimates of width. The results suggest that people use their visually perceived foot size to scale virtual spaces. Regardless of foot size, participants felt that they owned the feet rendered in the virtual world. Seeing disembodied, but motion-tracked, virtual feet affected spatial judgments, suggesting that the presentation of a single tracked body part is sufficient to produce similar effects on perception, as has been observed with the presence of fully co-located virtual self-avatars or other body parts in the past.
Spatiotemporal SIMT and Scalarization for Improving GPU Efficiency
Authors: Lucas Jan , Andersch Michael , Alvarez-Mesa Mauricio , Juurlink Ben
Published: September 2015

Temporal SIMT (TSIMT) has been suggested as an alternative to conventional (spatial) SIMT for improving GPU performance on branch-intensive code. Although TSIMT has been briefly mentioned before, it was not evaluated. We present a complete design and evaluation of TSIMT GPUs, along with the inclusion of scalarization and a combination of temporal and spatial SIMT, named Spatiotemporal SIMT (STSIMT). Simulations show that TSIMT alone results in a performance reduction, but a combination of scalarization and STSIMT yields a mean performance enhancement of 19.6% and improves the energy-delay product by 26.2% compared to SIMT.
Toward Simpler, not Simplistic, Quantification of Software Architecture and Metrics
Authors: Ozkaya Ipek , Nord Robert L. , Koziolek Heiko , Avgeriou Paris
Published: September 2015

Architects of complex software systems face the challenge of how best to assess the achievement of quality attributes and other key system drivers, how to reveal issues and risks early, and how to make decisions about architecture improvement. Software architecture quality has a large impact on this effort, but it is usually not assessed with quantitative measures. A software architecture metric quantifies architecture quality, value, and cost. While it is highly desirable to improve feedback between development and deployment through measurable means for intrinsic quality, value, and cost, efforts in software architecture quality measurement have lagged behind the body of work focusing on code quality. The goal of the Second International Workshop on Software Architecture and Metrics was to discuss progress on architecture and metrics, measurement, and analysis; to gather empirical evidence on the use and effectiveness of metrics; and to identify priorities for a research agenda.
ITiCSE conference report
Authors: Dagienė Valentina
Published: September 2015

The 20th Annual ITiCSE, held in Vilnius, Lithuania is over and mixed feelings are spread around attendees --- the cheeriness of productively spending several days together and the nostalgia for leaving both the known and the newly made friends.
Estimating the magnitude of near-membrane PDE4 activity in living cells
Authors: Xin Wenkuan , Feinstein Wei P. , Britain Andrea L. , Ochoa Cristhiaan D. , Zhu Bing , Richter Wito , Leavesley Silas J. , Rich Thomas C.
Published: September 2015

Recent studies have demonstrated that functionally discrete pools of phosphodiesterase (PDE) activity regulate distinct cellular functions. While the importance of localized pools of enzyme activity has become apparent, few studies have estimated enzyme activity within discrete subcellular compartments. Here we present an approach to estimate near-membrane PDE activity. First, total PDE activity is measured using traditional PDE activity assays. Second, known cAMP concentrations are dialyzed into single cells and the spatial spread of cAMP is monitored using cyclic nucleotide-gated channels. Third, mathematical models are used to estimate the spatial distribution of PDE activity within cells. Using this three-tiered approach, we observed two pharmacologically distinct pools of PDE activity, a rolipram-sensitive pool and an 8-methoxymethyl IBMX (8MM-IBMX)-sensitive pool. We observed that the rolipram-sensitive PDE (PDE4) was primarily responsible for cAMP hydrolysis near the plasma membrane. Finally, we observed that PDE4 was capable of blunting cAMP levels near the plasma membrane even when 100 μM cAMP were introduced into the cell via a patch pipette. Two compartment models predict that PDE activity near the plasma membrane, near cyclic nucleotide-gated channels, was significantly lower than total cellular PDE activity and that a slow spatial spread of cAMP allowed PDE activity to effectively hydrolyze near-membrane cAMP. These results imply that cAMP levels near the plasma membrane are distinct from those in other subcellular compartments; PDE activity is not uniform within cells; and localized pools of AC and PDE activities are responsible for controlling cAMP levels within distinct subcellular compartments.
Aerobic exercise training-induced changes in serum adropin level are associated with reduced arterial stiffness in middle-aged and older adults
Authors: Fujie Shumpei , Hasegawa Natsuki , Sato Koji , Fujita Satoshi , Sanada Kiyoshi , Hamaoka Takafumi , Iemitsu Motoyuki
Published: September 2015

Aging-induced arterial stiffening is reduced by aerobic exercise training, and elevated production of nitric oxide (NO) participates in this effect. Adropin is a regulator of endothelial NO synthase and NO release, and circulating adropin level decreases with age. However, the effect of habitual aerobic exercise on circulating adropin levels in healthy middle-aged and older adults remains unclear. We sought to determine whether serum adropin level is associated with exercise training-induced changes in arterial stiffness. First, in a cross-sectional study, we investigated the association between serum adropin level and both arterial stiffness and cardiorespiratory fitness in 80 healthy middle-aged and older subjects (65.6 ± 0.9 yr). Second, in an intervention study, we examined the effects of 8-wk aerobic exercise training on serum adropin level and arterial stiffness in 40 healthy middle-aged and older subjects (67.3 ± 1.0 yr) divided into two groups: aerobic exercise training and sedentary controls. In the cross-sectional study, serum adropin level was negatively correlated with carotid β-stiffness ( r = −0.437, P < 0.001) and positively correlated with plasma NOx level ( r = 0.493, P < 0.001) and cardiorespiratory fitness ( r = 0.457, P < 0.001). Serum adropin levels were elevated after the 8-wk aerobic exercise training intervention, and training-induced changes in serum adropin level were correlated with training-induced changes in carotid β-stiffness ( r = −0.399, P < 0.05) and plasma NOx level ( r = 0.623, P < 0.001). Thus the increase in adropin may participate in the exercise-induced reduction of arterial stiffness.
Coagulation changes during lower body negative pressure and blood loss in humans
Authors: Helmond Noud van , Johnson Blair D. , Curry Timothy B. , Cap Andrew P. , Convertino Victor A. , Joyner Michael J.
Published: September 2015

We tested the hypothesis that markers of coagulation activation are greater during lower body negative pressure (LBNP) than those obtained during blood loss (BL). We assessed coagulation using both standard clinical tests and thrombelastography (TEG) in 12 men who performed a LBNP and BL protocol in a randomized order. LBNP consisted of 5-min stages at 0, −15, −30, and −45 mmHg of suction. BL included 5 min at baseline and following three stages of 333 ml of blood removal (up to 1,000 ml total). Arterial blood draws were performed at baseline and after the last stage of each protocol. We found that LBNP to −45 mmHg is a greater central hypovolemic stimulus versus BL; therefore, the coagulation markers were plotted against central venous pressure (CVP) to obtain stimulus-response relationships using the linear regression line slopes for both protocols. Paired t-tests were used to determine whether the slopes of these regression lines fell on similar trajectories for each protocol. Mean regression line slopes for coagulation markers versus CVP fell on similar trajectories during both protocols, except for TEG α° angle (−0.42 ± 0.96 during LBNP vs. −2.41 ± 1.13°/mmHg during BL; P < 0.05). During both LBNP and BL, coagulation was accelerated as evidenced by shortened R-times (LBNP, 9.9 ± 2.4 to 6.2 ± 1.1; BL, 8.7 ± 1.3 to 6.4 ± 0.4 min; both P < 0.05). Our results indicate that LBNP models the general changes in coagulation markers observed during BL.
Sr2−xBaxTiO4:Eu3+, Gd3+: A Novel Blue Converting Yellow‐Emitting Phosphor for White Light‐Emitting Diodes
Authors: Dong Limin , Zhao Jiatong , Li Qin , Han Zhidong
Published: September 2015

A highly intense yellow‐emitting phosphor
Sr2−xBaxTiO4:Eu3+, Gd3+
peaking at 593–611 nm was synthesized by the sol‐gel method. XRD and SEM show that the samples are single phase and have irregular shape. The excitation wavelength matches well with that of the emission of the blue‐light‐emitting diode. The emission peaks at 593 and 611 nm are attributed to the transitions from the 5D0‐7F1 and 5D0‐7F2 of Eu3+ ions, respectively. Gd3+ was used as sensitizer, aiming at increasing the luminous intensity. A certain amount of Sr2+ and Ba2+ is contributed to the intensity of light emission.
Real-time Imaging of the Resection Bed Using a Handheld Probe to Reduce Incidence of Microscopic Positive Margins in Cancer Surgery
Authors: Erickson-Bhatt Sarah J. , Nolan Ryan M. , Shemonski Nathan D. , Adie Steven G. , Putney Jeffrey , Darga Donald , McCormick Daniel T. , Cittadine Andrew J. , Zysk Adam M. , Marjanovic Marina , Chaney Eric J. , Monroy Guillermo L. , South Fredrick A. , Cradock Kimberly A. , Liu Z. George , Sundaram Magesh , Ray Partha S. , Boppart Stephen A.
Published: September 2015

Wide local excision (WLE) is a common surgical intervention for solid tumors such as those in melanoma, breast, pancreatic, and gastrointestinal cancer. However, adequate margin assessment during WLE remains a significant challenge, resulting in surgical reinterventions to achieve adequate local control. Currently, no label-free imaging method is available for surgeons to examine the resection bed in vivo for microscopic residual cancer. Optical coherence tomography (OCT) enables real-time high-resolution imaging of tissue microstructure. Previous studies have demonstrated that OCT analysis of excised tissue specimens can distinguish between normal and cancerous tissues by identifying the heterogeneous and disorganized microscopic tissue structures indicative of malignancy. In this translational study involving 35 patients, a handheld surgical OCT imaging probe was developed for in vivo use to assess margins both in the resection bed and on excised specimens for the microscopic presence of cancer. The image results from OCT showed structural differences between normal and cancerous tissue within the resection bed following WLE of the human breast. The ex vivo images were compared with standard postoperative histopathology to yield sensitivity of 91.7% [95% confidence interval (CI), 62.5%–100%] and specificity of 92.1% (95% CI, 78.4%–98%). This study demonstrates in vivo OCT imaging of the resection bed during WLE with the potential for real-time microscopic image-guided surgery. Cancer Res; 75(18); 3706–12. ©2015 AACR.