bluuebunny/crossref_metadata_2025 huggingface dataset:
Dosimetric properties of radiophotoluminescent glass detector in low‐energy photon beams
Authors: Kadoya Noriyuki , Shimomura Kouhei , Kitou Satoshi , Shiota Yasuo , Fujita Yukio , Dobashi Suguru , Takeda Ken , Jingu Keiichi , Matsushita Haruo , Namito Yoshihito , Ban Syuichi , Koyama Syuji , Tabushi Katsuyoshi
Published: September 2012

Purpose:

A radiophotoluminescent glass rod dosimeter (RGD) has recently become commercially available. It is being increasingly used for dosimetry in radiotherapy to measure the absorbed dose including scattered low‐energy photons on the body surface of a patient and for postal dosimetry audit. In this article, the dosimetric properties of the RGD, including energy dependence of the dose response, reproducibly, variation in data obtained by the RGD for each energy, and angular dependence in low‐energy photons, are discussed.

Methods:

An RGD (GD‐301, Asahi Techno Glass Corporation, Shizuoka, Japan) was irradiated with monochromatic low‐energy photon beams generated by synchrotron radiation at Photon Factory, High Energy Accelerator Research Organization (KEK). The size of GD‐301 was 1.5 mm in diameter and 8.5 mm in length and the active dose readout volume being 1 mm diameter and 0.6 mm depth located 0.7 mm from the end of the detector. The energy dependence of the dose response and reproducibility and variation were investigated for RGDs irradiated with a plastic holder and those irradiated without the plastic holder. Response of the RGD was obtained by not only conventional single field irradiation but also bilateral irradiation. Angular dependence of the RGD was measured in the range of 0°–90° for 13, 17, 40, and 80 keV photon beams by conventional single field irradiation.

Results:

The dose responses had a peak at around 40 keV. For the energy range of less than 25 keV, all dose response curves steeply decreased in comparison with the ratio of mass energy absorption coefficient of the RGD to that of air. As for the reproducibility and variation in data obtained by the RGD, the coefficient of variance increased with decrease in photon energy. Furthermore, the variation for bilateral irradiation was less than that for single field irradiation. Regarding angular dependence of the RGD, for energies of 13 and 17 keV, the response decreased with increase in the irradiation angle, and the minimum values were 93.5% and 86%, respectively.

Conclusions:

Our results showed the dosimetric properties of the RGD, including the energy dependence of the dose response, reproducibly, variation, and angular dependence in low‐energy photons and suggest that the accuracy of the absorbed dose in low‐energy photons is affected by the readout method and the distribution of radiophotoluminescence centers in the RGD.
Automatic atlas‐based segmentation of the breast in MRI for 3D breast volume computation
Authors: Ortiz C. Gallego , Martel A. L.
Published: September 2012

Purpose:

Breast density is considered a significant risk factor and an important biomarker influencing the later risk of breast cancer. Prior breast segmentation is required when quantifying breast density with MRI in order to calculate the total breast volume and exclude nonbreast surrounding tissues. This paper describes an automatic 3D breast volume segmentation approach.

Methods:

The method is based on 3D local edge detection using phase congruency and Poisson surface reconstruction to extract the total breast volume. The boundary localization framework is integrated to a subsequent shape atlas‐based segmentation using a Laplacian framework.

Results:

The 3D segmentation achieves breast‐air and breast‐chest wall boundary localization errors with a median of 1.36 mm and 2.68 mm, respectively, and an average volume error of 153.8 cm3 when tested on 409 MRI datasets. Furthermore, the breast volume assessment technique will produce a 5.3% variability in the estimation of breast density in the tested population.

Conclusions:

The fully automated segmentation approach of the breast in MRI allows the computation of total breast volume, a step required for breast density assessment. The use of features invariant to image intensity and a shape atlas to reinforce shape consistency are attractive characteristics of the method. Error analysis demonstrates that 5.3% variability in the estimation of breast density incurred by the method is an acceptable trade‐off.
Using statistical measures for automated comparison of in‐beam PET data
Authors: Kuess Peter , Birkfellner Wolfgang , Enghardt Wolfgang , Helmbrecht Stephan , Fiedler Fine , Georg Dietmar
Published: September 2012

Purpose:

Positron emission tomography (PET) is considered to be the state of the art technique to monitor particle therapyin vivo. To evaluate the beam delivery the measured PET image is compared to a predicted β+‐distribution. Nowadays the range assessment is performed by a group of experts via visual inspection. This procedure is rather time consuming and requires well trained personnel. In this study an approach is presented to support human decisions in an automated and objective way.

Methods:

The automated comparison presented uses statistical measures, namely, Pearsonˈs correlation coefficient (PCC), to detect ion beam range deviations. The study is based on 12 in‐beam PET patient data sets recorded at GSI and 70 artificial beam range modifications per data set. The range modifications were 0, 4, 6, and 10 mm water equivalent path length (WEPL) in positive and negative beam directions. The reference image to calculate the PCC was both an unmodified simulation of the activity distribution (Test 1) and a measured in‐beam PET image (Test 2). Based on the PCCs sensitivity and specificity were calculated. Additionally the difference between modified and unmodified data sets was investigated using the Wilcoxon rank sum test.

Results:

In Test 1 a sensitivity and specificity over 90% was reached for detecting modifications of ±10 and ±6 mm WEPL. Regarding Test 2 a sensitivity and specificity above 80% was obtained for modifications of ±10 and −6 mm WEPL. The limitation of the method was around 4 mm WEPL.

Conclusions:

The results demonstrate that the automated comparison using PCC provides similar results in terms of sensitivity and specificity compared to visual inspections of in‐beam PET data. Hence the method presented in this study is a promising and effective approach to improve the efficiency in the clinical workflow in terms of particle therapy monitoring by means of PET.
A Simple Interactive Software Package for Plotting, Animating, and Calculating
Authors: Engelhardt Larry
Published: September 2012

We introduce a new open source (free) software package that provides a simple, highly interactive interface for carrying out certain mathematical tasks that are commonly encountered in physics. These tasks include plotting and animating functions, solving systems of coupled algebraic equations, and basic calculus (differentiating and integrating functions of a single variable). This package was created using Easy Java Simulations (Ejs),1 so we will refer to it simply as Ejs-Math. It can be downloaded from the Open Source Physics collection of the comPADRE digital library.2
Units, Jargon, g-forces, and Squirting Blood
Authors: Milanick Mark
Published: September 2012

Two of the most frustrating things for me as a teacher are the way units and jargon can get in the way of understanding concepts. When I teach pre-nursing and medical students about blood pressure, they end up memorizing a lot of information that would be obvious if they had remembered some of their basic physics—particularly the ability to change units. Of course, the other solution would be to use units that make sense to the students. Some non-majors taking physics classes are thinking about careers in the medical field, but often don't see the connection between physics and their interest in medicine. However, there are a number of ways instructors can build on students' interests to help them explore real-world applications of physics and medicine. This laboratory exercise provides an example of one such connection, by engaging students in considering why large g-forces may cause individuals to “black out.” We have used this activity with success in a pre-nursing physiology class and believe it could be easily adapted for teachers of high school physics.
Estimating the Size of Onion Epidermal Cells from Diffraction Patterns
Authors: Groff Jeffrey R.
Published: September 2012

Bioscience and premedical profession students are a major demographic served by introductory physics courses at many colleges and universities. Exposing these students to biological applications of physical principles will help them to appreciate physics as a useful tool for their future professions. Here I describe an experiment suitable for introductory physics where principles of wave optics are applied to probe the size of onion epidermal cells. The epidermis tissue is composed of cells of relatively uniform size and shape (Fig. 1) so the tissue acts like a one-dimensional transmission diffraction grating. The diffraction patterns generated when a laser beam passes through the tissue (Fig. 2) are analyzed and an estimate of the average width of individual onion epidermal cells is calculated. The results are compared to direct measurements taken using a light microscope. The use of microscopes and plant-cell tissue slides creates opportunities for cross-discipline collaboration between physics and biology instructors.
A first-order k-space model for elastic wave propagation in heterogeneous media
Authors: Firouzi K. , Cox B. T. , Treeby B. E. , Saffari N.
Published: September 2012

A pseudospectral model of linear elastic wave propagation is described based on the first order stress-velocity equations of elastodynamics. k-space adjustments to the spectral gradient calculations are derived from the dyadic Green’s function solution to the second-order elastic wave equation and used to (a) ensure the solution is exact for homogeneous wave propagation for timesteps of arbitrarily large size, and (b) also allows larger time steps without loss of accuracy in heterogeneous media. The formulation in k-space allows the wavefield to be split easily into compressional and shear parts. A perfectly matched layer (PML) absorbing boundary condition was developed to effectively impose a radiation condition on the wavefield. The staggered grid, which is essential for accurate simulations, is described, along with other practical details of the implementation. The model is verified through comparison with exact solutions for canonical examples and further examples are given to show the efficiency of the method for practical problems. The efficiency of the model is by virtue of the reduced point-per-wavelength requirement, the use of the fast Fourier transform (FFT) to calculate the gradients in k space, and larger time steps made possible by the k-space adjustments.
Numerical and analytical solutions for sound propagation and absorption in porous media at high sound pressure levels
Authors: Zhang Bo , Chen Tianning , Zhao Yuyuan , Zhang Weiyong , Zhu Jian
Published: September 2012

On the basis of the work of Wilson et al. [J. Acoust. Soc. Am. 84, 350–359 (1988)], a more exact numerical approach was constructed for predicting the nonlinear sound propagation and absorption properties of rigid porous media at high sound pressure levels. The numerical solution was validated by the experimental results for sintered fibrous porous steel samples and its predictions were compared with the numerical solution of Wilson et al. An approximate analytical solution was further put forward for the normalized surface acoustic admittance of rigid air-saturated porous materials with infinite thickness, based on the wave perturbation method developed by Lambert and McIntosh [J. Acoust. Soc. Am. 88, 1950–1959 (1990)]. Comparisons were made with the numerical results.
Frequency difference limens at high frequencies: Evidence for a transition from a temporal to a place code
Authors: Moore Brian C. J. , Ernst Stephan M. A.
Published: September 2012

It is commonly believed that difference limens for frequency (DLFs) for pure tones depend on a temporal mechanism (phase locking) for frequencies up to 4–5 kHz and a place mechanism at higher frequencies. The DLFs predicted from a place mechanism, expressed as a proportion of center frequency (Δf/f), should be approximately invariant with frequency at medium to high frequencies. If there is a transition from a temporal to a place mechanism, Δf/f should increase with increasing center frequency until the transition occurs, and then reach a plateau. Published data do not show such an effect. In this study, DLFs were measured for center frequencies from 2 to 14 kHz, using earphones designed to produce a flat response at the eardrum. The level of every tone was varied over a range of ±4 dB, to reduce loudness cues. The value of Δf/f increased progressively from 2 to 8 kHz, but did not change significantly for frequencies from 8 to 14 kHz. The results are consistent with the idea that there is a transition from a temporal to a place mechanism at about 8 kHz, rather than at 4–5 kHz, as is commonly assumed.
Impact of talker variability on word recognition in non-native listeners
Authors: van Dommelen Wim A. , Hazan Valerie
Published: September 2012

This study investigates the perception of English words produced by 45 native talkers presented in moderate noise to native Norwegian listeners. The relative intelligibility of individual talkers is compared with that obtained for native listeners in order to determine whether intrinsic talker clarity is determined by global acoustic-phonetic characteristics. Talker intelligibility was strongly correlated across native and non-native listeners although the acoustic-phonetic characteristics that correlated with intelligibility varied across the two groups. For both groups, intelligibility was correlated with an amount of energy in the mid-frequency region, but whereas mean word duration was another relevant factor for the natives it was the F2 range in the vowel space for the non-natives. There was also a strong correlation across groups as to the lexical items most often misperceived. Results for two different listening conditions (recognition of isolated words vs triplets) suggested that non-native performance was to a certain extent hampered by increased cognitive load in the triplet condition.
Silky sifaka (Propithecus candidus) “zzuss” vocalizations: Sexual dimorphism, individuality, and function in the alarm call of a monomorphic lemur
Authors: Patel Erik R. , Owren Michael J.
Published: September 2012

Vocalizations of Madagascar’s lemurs have generally been less investigated than those of other primate groups, with virtually no information available about calling in the silky sifaka (Propithecus candidus), a large rainforest species. Current work examined the “zzuss” vocalization, one of the most common and loudest sounds produced by this monomorphic species, and included 160 calls from nine adults (five males, four females) in three groups. Analyses focused on overall acoustic features, individual and sex differences, call usage, and likely function. Acoustically, the calls included separable turbulent noise and tonal components, with the later often marked by frequency jumps and dramatic frequency modulation. Male and female zzuss calls differed most in F0- and amplitude-related features, characteristics that are relatively unconstrained by overall body size. All measures differed among individual callers, with F0-related variables again playing the largest role. Based on usage, these calls most likely function both as generalized alarm and group-coordination signals. The sounds were thus of interest in several regards, including showing sexual differentiation in the absence of other dimorphisms, exhibiting primarily F0-based differentiation in both sex- and individual-based comparisons, and combining apparent alarm and coordination functions across a variety of contexts.
Consistent modeling of boundaries in acoustic finite-difference time-domain simulations
Authors: Häggblad Jon , Engquist Björn
Published: September 2012

The finite-difference time-domain method is one of the most popular for wave propagation in the time domain. One of its advantages is the use of a structured staggered grid, which makes it simple and efficient on modern computer architectures. A drawback, however, is the difficulty in approximating oblique boundaries, having to resort to staircase approximations. In many scattering problems this means that the grid resolution required to obtain an accurate solution is much higher than what is dictated by propagation in a homogeneous material. In this paper zero boundary data are considered, first for the velocity and then the pressure. These two forms of boundary conditions model perfectly rigid and pressure-release boundaries, respectively. A simple and efficient method to consistently model curved rigid boundaries in two dimensions was developed in Tornberg and Engquist [J. Comput. Phys. 227, 6922–6943 (2008)]. Here this treatment is generalized to three dimensions. Based on the approach of this method, a technique to model pressure-release surfaces with second order accuracy and without additional restriction on the timestep is also introduced. The structure of the standard method is preserved, making it easy to use in existing solvers. The effectiveness is demonstrated in several numerical tests.
Combining time of flight and diffraction tomography for high resolution breast imaging: Initial invivo results (L)
Authors: Huthwaite P. , Simonetti F. , Duric N.
Published: September 2012

Ultrasound tomography (UST) is being developed to address the limitations of mammography in breast cancer detection. Central to the success of UST is the possibility of obtaining high-resolution images of tissue mechanical properties across the whole breast. A recent paper [Huthwaite and Simonetti, J. Acoust. Soc. Am. 130, 1721–1734 (2011)] made use of a numerical phantom to demonstrate that sufficient image resolution can be obtained by simply treating refraction and diffraction effects in consecutive steps through the combination of ray-based time of flight and diffraction tomography. This letter presents the first experimental demonstration of the method using phantom and invivo data from a cancer patient.
Input impedance in flow ducts: Theory and measurement
Authors: Rodriguez S. , Gibiat V. , Lefebvre A. , Guilain Stephane
Published: September 2012

This paper presents both a theoretical and an experimental investigation of the influence of the mean flow on the input impedance of a duct. The input impedance of an axisymetrical flow duct is calculated, taking into account the convective effect of a uniform flow, the dissipative effect of a turbulent flow and the radiation in an open jet. Each of these effects is separately studied. An experimental apparatus has been specifically designed to lower flow noise on the transducers, taking advantage of the Two-Microphone-Three-Calibration (TMTC) method [V. Gibiat and F. Laloë, J. Acoust. Soc. Am. 88, 2533–2545 (1990)], whose full calibration process allows any geometry for the measurement head. Theory and experiments are compared for a 1 m long cylindrical duct carrying a flow whose Mach number equals up to 0.15. The resonant frequencies are in close agreement, within 3%. The relative evolution of the magnitude maxima with increasing flow are in good agreement, within 10%. Despite similar tendencies when modifying the mean flow velocity, the amplitude of variation of the magnitude is 2 to 5 times smaller in the experiments.
Cross-imaging system comparison of backscatter coefficient estimates from a tissue-mimicking material
Authors: Nam Kibo , Rosado-Mendez Ivan M. , Wirtzfeld Lauren A. , Kumar Viksit , Madsen Ernest L. , Ghoshal Goutam , Pawlicki Alexander D. , Oelze Michael L. , Lavarello Roberto J. , Bigelow Timothy A. , Zagzebski James A. , O’Brien William D. , Hall Timothy J.
Published: September 2012

A key step toward implementing quantitative ultrasound techniques in a clinical setting is demonstrating that parameters such as the ultrasonic backscatter coefficient (BSC) can be accurately estimated independent of the clinical imaging system used. In previous studies, agreement in BSC estimates for well characterized phantoms was demonstrated across different laboratory systems. The goal of this study was to compare the BSC estimates of a tissue mimicking sample measured using four clinical scanners, each providing RF echo data in the 1-15 MHz frequency range. The sample was previously described and characterized with single-element transducer systems. Using a reference phantom for analysis, excellent quantitative agreement was observed across the four array-based imaging systems for BSC estimates. Additionally, the estimates from data acquired with the clinical systems agreed with theoretical predictions and with estimates from laboratory measurements using single-element transducers.
Measurement of reverberation gain in an urban environment
Authors: Mijić Miomir , Šumarac Pavlović Dragana
Published: September 2012

Multipath propagation within an urban area introduces a specific type of reverberation in response to sound excitation. That appearance affects the level of ambient noise produced by strong sound sources. In this paper, the signals recorded during the 1999 bombing of Belgrade were used to analyze the characteristics of reverberation in that urban environment. Six recorded signals were selected among more than 50 explosions recorded at that time. Due to the impulse nature of sound sources, the recorded signals represent the impulse responses of that area. The measured reverberation time T30 is about 7 ± 1 s in octaves between 31.5 Hz and 1 kHz. There is a variation of decay slope in time that is verified by differences between values of T10 and T30. The reverberation gain calculated from recorded signals is 2–7 dB, depending on the global position of the sound excitation point as well as its micro-location according to its position among the surrounding buildings. A variation of gain over octave bands is in the interval of approximately 3 dB. Information about reverberation gain in urban environment can be useful in a quick estimation of noise level produced by strong sound sources in a large area of urban environment.
Extrapolating from Animals to Humans
Authors: Ioannidis John P. A.
Published: September 2012

Clinical effectiveness for interventions in humans can only be speculated from animal studies.
THE ONION DIAGRAM: A VORONOI-LIKE TESSELLATION OF A PLANAR LINE SPACE AND ITS APPLICATIONS
Authors: BAE SANG WON , SHIN CHAN-SU
Published: September 2012

Given a set S of weighted points in the plane, we consider two problems dealing with lines in ℝ2 under the weighted Euclidean distance: (1) Preprocess S into a data structure that efficiently finds a nearest point among S to a query line. (2) Find an optimal line that maximizes the minimum of the weighted distance to any point of S. The latter problem is also known as the obnoxious line location problem. We introduce a unified approach to both problems based on a new geometric transformation that maps lines in the plane to points in a line space. It turns out that our transformation, together with its target space, well describes the proximity relations between given weighted points S and every line in ℝ2. We define a Voronoi-like tessellation on the line space and investigate its geometric, combinatorial, and computational properties. As its direct applications, we obtain several new algorithmic results on the two problems. We also show that our approach extends to weighted line segments and weighted polygons.
APPROXIMATE SHORTEST HOMOTOPIC PATHS IN WEIGHTED REGIONS
Authors: CHENG SIU-WING , JIN JIONGXIN , VIGNERON ANTOINE , WANG YAJUN
Published: September 2012

A path P between two points s and t in a polygonal subdivision [Formula: see text] with obstacles and weighted regions defines a class of paths that can be deformed to P without passing over any obstacle. We present the first algorithm that, given P and a relative error tolerance ε ϵ (0, 1), computes a path from this class with cost at most 1 + ε times the optimum. The running time is [Formula: see text], where k is the number of segments in P and h and n are the numbers of obstacles and vertices in [Formula: see text], respectively. The constant in the running time of our algorithm depends on some geometric parameters and the ratio of the maximum region weight to the minimum region weight.
What can gold farmers teach us about criminal networks?
Authors: Keegan Brian , Ahmad Muhammad Aurangzeb , Williams Dmitri , Srivastava Jaideep , Contractor Noshir
Published: September 2012

By observing how covert financial networks operate in online games like World of Warcraft, we can learn about how they might function offline.
Sustainable data centers
Authors: Weihl Bill , Teetzel Erik , Clidaras Jimmy , Malone Chris , Kava Joe , Ryan Michael
Published: September 2012

How Google addresses energy and environment issues as they pertain to its global data centers.
Sourcemap
Authors: Bonanni Leo
Published: September 2012

Industry and consumers need tools to help make decisions that are good for communities and for the environment.
From Neural Networks to Deep Learning
Authors: Laserson Jonathan
Published: September 2012

Pondering the brain with the help of machine learning expert Andrew Ng and researcher-turned-author-turned-entrepreneur Jeff Hawkins.
Using software to liberate U.S. case law
Authors: Yu Harlan , Schultze Stephen
Published: September 2012

Although public information is open, it is not always easily accessible.
Mastering real-time big data with stream processing chains
Authors: Bonino Dario , De Russis Luigi
Published: September 2012

To conciliate application logic concerns with event handling performance, we introduce the spChains processing framework.
Parallel machine learning on big data
Authors: Langford John
Published: September 2012

On algorithms for parallel machine learning, and why they need to be more efficient.
Efficient performance evaluation of memory hierarchy for highly multithreaded graphics processors
Authors: Baghsorkhi Sara S. , Gelado Isaac , Delahaye Matthieu , Hwu Wen-mei W.
Published: September 2012

With the emergence of highly multithreaded architectures, performance monitoring techniques face new challenges in efficiently locating sources of performance discrepancies in the program source code. For example, the state-of-the-art performance counters in highly multithreaded graphics processing units (GPUs) report only the overall occurrences of microarchitecture events at the end of program execution. Furthermore, even if supported, any fine-grained sampling of performance counters will distort the actual program behavior and will make the sampled values inaccurate. On the other hand, it is difficult to achieve high resolution performance information at low sampling rates in the presence of thousands of concurrently running threads. In this paper, we present a novel software-based approach for monitoring the memory hierarchy performance in highly multithreaded general-purpose graphics processors. The proposed analysis is based on memory traces collected for snapshots of an application execution. A trace-based memory hierarchy model with a Monte Carlo experimental methodology generates statistical bounds of performance measures without being concerned about the exact inter-thread ordering of individual events but rather studying the behavior of the overall system. The statistical approach overcomes the classical problem of disturbed execution timing due to fine-grained instrumentation. The approach scales well as we deploy an efficient parallel trace collection technique to reduce the trace generation overhead and a simple memory hierarchy model to reduce the simulation time. The proposed scheme also keeps track of individual memory operations in the source code and can quantify their efficiency with respect to the memory system. A cross-validation of our results shows close agreement with the values read from the hardware performance counters on an NVIDIA Tesla C2050 GPU. Based on the high resolution profile data produced by our model we optimized memory accesses in the sparse matrix vector multiply kernel and achieved speedups ranging from 2.4 to 14.8 depending on the characteristics of the input matrices.
A hybrid approach of OpenMP for clusters
Authors: Kwon Okwan , Jubair Fahed , Eigenmann Rudolf , Midkiff Samuel
Published: September 2012

We present the first fully automated compiler-runtime system that successfully translates and executes OpenMP shared-address-space programs on laboratory-size clusters, for the complete set of regular, repetitive applications in the NAS Parallel Benchmarks. We introduce a hybrid compiler-runtime translation scheme. Compared to previous work, this scheme features a new runtime data flow analysis and new compiler techniques for improving data affinity and reducing communication costs. We present and discuss the performance of our translated programs, and compare them with the performance of the MPI, HPF and UPC versions of the benchmarks. The results show that our translated programs achieve 75% of the hand-coded MPI programs, on average.
Revisiting the combining synchronization technique
Authors: Fatourou Panagiota , Kallimanis Nikolaos D.
Published: September 2012

Fine-grain thread synchronization has been proved, in several cases, to be outperformed by efficient implementations of the combining technique where a single thread, called the
combiner
, holding a coarse-grain lock, serves, in addition to its own synchronization request, active requests announced by other threads while they are waiting by performing some form of spinning. Efficient implementations of this technique significantly reduce the cost of synchronization, so in many cases they exhibit much better performance than the most efficient finely synchronized algorithms.

In this paper, we revisit the combining technique with the goal to discover where its real performance power resides and whether or how ensuring some desired properties (e.g., fairness in serving requests) would impact performance. We do so by presenting two new implementations of this technique; the first (CC-Synch) addresses systems that support coherent caches, whereas the second (DSM-Synch) works better in cacheless NUMA machines. In comparison to previous such implementations, the new implementations (1) provide bounds on the number of remote memory references (RMRs) that they perform, (2) support a stronger notion of fairness, and (3) use simpler and less basic primitives than previous approaches. In all our experiments, the new implementations outperform by far all previous state-of-the-art combining-based and fine-grain synchronization algorithms. Our experimental analysis sheds light to the questions we aimed to answer.

Several modern multi-core systems organize the cores into clusters and provide fast communication within the same cluster and much slower communication across clusters. We present an hierarchical version of CC-Synch, called H-Synch which exploits the hierarchical communication nature of such systems to achieve better performance. Experiments show that H-Synch significantly outper forms previous state-of-the-art hierarchical approaches.

We provide new implementations of common shared data structures (like stacks and queues) based on CC-Synch, DSM-Synch and H-Synch. Our experiments show that these implementations outperform by far all previous (fine-grain or combined-based) implementations of shared stacks and queues.
FlexBFS
Authors: Liu Gu , An Hong , Han Wenting , Li Xiaoqiang , Sun Tao , Zhou Wei , Wei Xuechao , Tang Xulong
Published: September 2012

In this paper, we present FlexBFS, a parallelism-aware implementation for breadth-first search on GPU. Our implementation can adjust the computation resources according to the feedback of available parallelism dynamically. We also optimized our program in three ways: (1)a simplified two-level queue management,(2)a combined kernel strategy and (3)a high-degree vertices specialization approach. Our experimental results show that it can achieve 3~20 times speedup against the fastest serial version, and can outperform the TBB based multi-threading CPU version and the previous most effective GPU version on all types of input graphs.
An overview of Medusa
Authors: Zhong Jianlong , He Bingsheng
Published: September 2012

Graphs are the de facto data structures for many applications, and efficient graph processing is a must for the application performance. GPUs have an order of magnitude higher computational power and memory bandwidth compared to CPUs and have been adopted to accelerate several common graph algorithms. However, it is difficult to write correct and efficient GPU programs and even more difficult for graph processing due to the irregularities of graph structures. To address those difficulties, we propose a programming framework named Medusa to simplify graph processing on GPUs. Medusa offers a small set of APIs, based on which developers can define their application logics by writing sequential code without awareness of GPU architectures. The Medusa runtime system automatically executes the developer defined APIs in parallel on the GPU, with a series of graph-centric optimizations. This poster gives an overview of Medusa, and presents some preliminary results.
Optimizing remote accesses for offloaded kernels
Authors: Alias Christophe , Darte Alain , Plesco Alexandru
Published: September 2012

In the context of the high-level synthesis (HLS) of regular kernels offloaded to FPGA and communicating with an external DDR memory, we show how to automatically generate adequate communicating processes for optimizing the transfer of remote data. This requires a generalized form of communication coalescing where data can be transferred from the external memory even when this memory is not fully up-to-date. Experiments with Altera HLS tools demonstrate that this automatization, based on advanced polyhedral code analysis and code generation techniques, can be used to efficiently map C kernels to FPGA, by generating, entirely at C level, all the necessary glue (the communication processes), which is compiled with the same HLS tool as for the computation kernel.
The boat hull model
Authors: Nugteren Cedric , Corporaal Henk
Published: September 2012

Multi-core and many-core were already major trends for the past six years, and are expected to continue for the next decades. With these trends of parallel computing, it becomes increasingly difficult to decide on which architecture to run a given application.

In this work, we use an algorithm classification to predict performance
prior
to algorithm implementation. For this purpose, we modify the
roofline model
to include class information. In this way, we enable architectural choice through performance prediction prior to the development of architecture specific code. The new model, the
boat hull model
, is demonstrated using a GPU as a target architecture. We show for 6 example algorithms that performance is predicted accurately without requiring code to be available.
OpenCL as a unified programming model for heterogeneous CPU/GPU clusters
Authors: Kim Jungwon , Seo Sangmin , Lee Jun , Nah Jeongho , Jo Gangwon , Lee Jaejin
Published: September 2012

In this paper, we propose an OpenCL framework for heterogeneous CPU/GPU clusters, and show that the framework achieves both high performance and ease of programming. The framework provides an illusion of a single system for the user. It allows the application to utilize multiple heterogeneous compute devices, such as multicore CPUs and GPUs, in a remote node as if they were in a local node. No communication API, such as the MPI library, is required in the application source. We implement the OpenCL framework and evaluate its performance on a heterogeneous CPU/GPU cluster that consists of one host node and nine compute nodes using eleven OpenCL benchmark applications.
NDetermin
Authors: Burnim Jacob , Elmas Tayfun , Necula George , Sen Koushik
Published: September 2012

Nondeterministic Sequential (NDSeq) specifications have been proposed as a means for separating the testing, debugging, and verifying of a program's parallelism correctness and its sequential functional correctness. In this work, we present a technique that, given a few representative executions of a parallel program, combines dynamic data flow analysis and Minimum-Cost Boolean Satisfiability (MinCostSAT) solving for automatically inferring a likely NDSeq specification for the parallel program. For a number of Java benchmarks, our tool NDetermin infers equivalent or stronger NDSeq specifications than those previously written manually.
Concurrent breakpoints
Authors: Park Chang-Seo , Sen Koushik
Published: September 2012

In program debugging, reproducibility of bugs is a key requirement. Unfortunately, bugs in concurrent programs are notoriously difficult to reproduce because bugs due to concurrency happen under very specific thread schedules and the likelihood of taking such corner-case schedules during regular testing is very low. We propose concurrent breakpoints, a light-weight and programmatic way to make a concurrency bug reproducible. We describe a mechanism that helps to hit a concurrent breakpoint in a concurrent execution with high probability. We have implemented concurrent breakpoints as a light-weight library for Java and C/C++ programs. We have used the implementation to deterministically reproduce several known non-deterministic bugs in real-world concurrent Java and C/C++ programs with almost 100% probability.
Establishing a Miniapp as a programmability proxy
Authors: Stone Andrew , Dennis John , Strout Michelle
Published: September 2012

Miniapps serve as test beds for prototyping and evaluating new algorithms, data structures, and programming models before incorporating such changes into larger applications. For the miniapp to accurately predict how a prototyped change would affect a larger application it is necessary that the miniapp be shown to serve as a proxy for that larger application. Although many benchmarks claim to proxy the performance for a set of large applications, little work has explored what criteria must be met for a benchmark to serve as a proxy for examining programmability. In this poster we describe criteria that can be used to establish that a miniapp serves as a performance and programmability proxy.
Performance analysis of parallel constraint-based local search
Authors: Caniou Yves , Diaz Daniel , Richoux Florian , Codognet Philippe , Abreu Salvador
Published: September 2012

We present a parallel implementation of a constraint-based local search algorithm and investigate its performance results for hard combinatorial optimization problems on two different platforms up to several hundreds of cores. On a variety of classical CSPs benchmarks, speedups are very good for a few tens of cores, and good up to a hundred cores. More challenging problems derived from reallife applications (Costas array) shows even better speedups, nearly optimal up to 256 cores.
Antibiotic Resistance ofEscherichia coliSerotypes from Cochin Estuary
Authors: Sukumaran Divya P. , Durairaj Srinivasan , Abdulla Mohamed Hatha
Published: September 2012

This study aimed at detecting the prevalence of antibiotic-resistant serotypes ofEscherichia coliin Cochin estuary, India.E. colistrains were isolated during the period January 2010–December 2011 from five different stations set at Cochin estuary. Water samples from five different stations in Cochin estuary were collected on a monthly basis for a period of two years. Isolates were serotyped, antibiogram-phenotyped for twelve antimicrobial agents, and genotyped by polymerase chain reaction foruidgene that codes forβ-D-glucuronidase. TheseE. colistrains from Cochin estuary were tested against twelve antibiotics to determine the prevalence of multiple antibiotic resistance among them. The results revealed that more than 53.33% of the isolates were multiple antibiotic resistant. Thirteen isolates showed resistance to sulphonamides and two of them contained thesul1 gene. Class 1 integrons were detected in twoE. colistrains which were resistant to more than seven antibiotics. In the present study, O serotyping, antibiotic sensitivity, and polymerase chain reaction were employed with the purpose of establishing the present distribution of multiple antibiotic-resistant serotypes, associated withE. coliisolated from different parts of Cochin estuary.
Temperature and H/D Isotopic Effects in the IR Spectra of the Hydrogen Bond in Solid-State 2-Furanacetic Acid and 2-Furanacrylic Acid
Authors: Flakus Henryk T. , Jarczyk-Jędryka Anna
Published: September 2012

Polarized IR spectra of 2-furanacetic acid and of 2-furanacrylic acid crystals were measured at 293 K and 77 K in the vO−H and vO−H band frequency ranges. The corresponding spectra of the two individual systems strongly differ, one from the other, by the corresponding band shapes as well as by the temperature effect characterizing the bands. The crystal spectral properties remain in a close relation with the electronic structure of the two different molecular systems. We show that a vibronic coupling mechanism involving the hydrogen bond protons and the electrons on the π-electronic systems in the molecules determines the way in which the vibrational exciton coupling between the hydrogen bonds in the carboxylic acid dimers occurs. A strong coupling in 2-furanacrylic acid dimers prefers a “tail-to-head-” type Davydov coupling widespread by the π-electrons. A weak through-space coupling in 2-furanacetic acid dimers is responsible for a “side-to-side-” type coupling. The relative contribution of each exciton coupling mechanism in the dimer spectra generation is temperature and the molecular electronic structure dependent. This explains the observed difference in the temperature-induced evolution of the compared spectra.
Almost Sure Stability and Stabilization for Hybrid Stochastic Systems with Time‐Varying Delays
Authors: Yang Hua , Shu Huisheng , Kan Xiu , Che Yan
Published: September 2012

The problems of almost sure (a.s.) stability and a.s. stabilization are investigated for hybrid stochastic systems (HSSs) with time‐varying delays. The different time‐varying delays in the drift part and in the diffusion part are considered. Based on nonnegative semimartingale convergence theorem, Hölder’s inequality, Doob’s martingale inequality, and Chebyshev’s inequality, some sufficient conditions are proposed to guarantee that the underlying nonlinear hybrid stochastic delay systems (HSDSs) are almost surely (a.s.) stable. With these conditions, a.s. stabilization problem for a class of nonlinear HSDSs is addressed through designing linear state feedback controllers, which are obtained in terms of the solutions to a set of linear matrix inequalities (LMIs). Two numerical simulation examples are given to show the usefulness of the results derived.
Dynamic Economic Dispatch Using Hybrid DE‐SQP for Generating Units with Valve‐Point Effects
Authors: Elaiw A. M. , Xia X. , Shehata A. M.
Published: September 2012

This paper presents hybrid differential evolution (DE) and sequential quadratic programming (SQP) for solving the dynamic economic dispatch (DED) problem for generating units with valve‐point effects. DE is used as a global optimizer and SQP is used as a fine tuning to determine the optimal solution at the final. The feasibility of the proposed method is validated with five‐and ten‐unit test systems. Results obtained by DE‐SQP method are compared with other techniques in the literature.
On the Sets of Convergence for Sequences of the q‐Bernstein Polynomials with q > 1
Authors: Ostrovska Sofiya , Özban Ahmet Yaşar
Published: September 2012

The aim of this paper is to present new results related to the convergence of the sequence of the q‐Bernstein polynomials {Bn,q(f; x)} in the case q > 1, where f is a continuous function on [0,1]. It is shown that the polynomials converge to f uniformly on the time scale , and that this result is sharp in the sense that the sequence may be divergent for all x ∈ R∖𝕁q. Further, the impossibility of the uniform approximation for the Weierstrass‐type functions is established. Throughout the paper, the results are illustrated by numerical examples.
Reoperation following Pancreaticoduodenectomy
Authors: Reddy J. R. , Saxena R. , Singh R. K. , Pottakkat B. , Prakash A. , Behari A. , Gupta A. K. , Kapoor V. K.
Published: September 2012

Introduction. The literature on reoperation following pancreaticoduodenectomy is sparse and does not address all concerns.Aim. To analyze the incidence, causes, and outcome of patients undergoing reoperations following pancreaticoduodenectomy.Methods. Retrospective analysis of 520 consecutive patients undergoing pancreaticoduodenectomy from May 1989 to September 2010.Results. 96 patients (18.5%) were reoperated; 72 were early, 18 were late, and 6 underwent both early and late reoperations. Indications for early reoperation were post pancreatectomy hemorrhage in 53 (68%), pancreatico-enteric anastomotic leak in 10 (13%), hepaticojejunostomy leak in 3 (3.8%), duodenojejunostomy leak in 4 (5%), intestinal obstruction in 1 (1.2%) and miscellaneous causes in 7 (9%). Patients reoperated early did not fare poorly on long-term follow up. Indications for late reoperations were complications of index surgery (n= 12), recurrence of the primary disease (n= 8), complications of adjuvant radiotherapy (n= 3), and gastrointestinal bleed (n= 1). The median survival of 16 patients reoperated late without recurrent disease was 49 months.Conclusion. Early reoperations following pancreaticoduodenectomy, commonly for post pancreatectomy hemorrhage, carries a high mortality due to associated sepsis, but has no impact on long-term survival. Long-term complications related to pancreaticoduodenectomy and adjuvant radiotherapy can be managed successfully with good results.
Methods for Assessing Expiratory Flow Limitation during Tidal Breathing in COPD Patients
Authors: Koulouris Nickolaos G. , Kaltsakas Georgios , Palamidas Anastasios F. , Gennimata Sofia-Antiopi
Published: September 2012

Patients with severe COPD often exhale along the same flow-volume curve during quite breathing as during forced expiratory vital capacity manoeuvre, and this has been taken as indicating expiratory flow limitation at rest (EFLT). Therefore,EFLT, namely, attainment of maximal expiratory flow during tidal expiration, occurs when an increase in transpulmonary pressure causes no increase in expiratory flow.EFLTleads to small airway injury and promotes dynamic pulmonary hyperinflation with concurrent dyspnoea and exercise limitation. In fact,EFLToccurs commonly in COPD patients (mainly in GOLD III and IV stage) in whom the latter symptoms are common. The existing up-to-date physiological methods for assessing expiratory flow limitation (EFLT) are reviewed in the present work. Among the currently available techniques, the negative expiratory pressure (NEP) has been validated in a wide variety of settings and disorders. Consequently, it should be regarded as a simple, non invasive, most practical, and accurate new technique.