bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetic reversal history of Pleistocene sediments at Old Crow, northwestern Yukon Territory
Authors: Pearce G. W. , Westgate John A. , Robertson Susan
Published: March 2010

The banks of the Porcupine River near Old Crow in the unglaciated part of the northern Yukon consist of about 55 m of interbedded fluvial and lacustrine gravels, sands, silts, and clays. This sequence was sampled closely for palaeomagnetic analysis and the sediments were found to possess a natural remanent magnetization (NRM) that is stable in direction with mean destructive fields of 200–300 Oe (16–24 kA/m). Therefore, good palaeomagnetic data can be obtained from sediments that have been subjected to permafrost conditions, although some samples show disturbance of NRM directions by cryoturbation.Magnetic polarity transitions are centred at 17 and 26 m above river level and the 15 samples between them define an interval of reversed polarity of considerable duration. The behaviour of NRM during the transition periods is complex with declination switching abruptly by 180° but with the inclination displaying very erratic variation over a considerable time. This may be caused by mixing in single samples of components of NRM with ages that straddle the transition—a situation that would be possible if NRM were post-depositional in origin and so could be locked in at times long after sedimentation.Sedimentological, palaeobotanical, and palaeomagnetic data all support the presence of a major unconformity in the middle portion of the sedimentary sequence. This unconformity lies at the top of the transition that closes the reversed episode so that the sediments below it are likely older than 700 000 years.These results demonstrate that palaeomagnetic studies on the sedimentary sequences exposed in the many isolated sites within the Old Crow region should greatly facilitate their correlation and indirect dating, effecting thereby an improved understanding of the recent geological history of this anthropologically important area.
Aminostratigraphy of Quaternary marine and glaciomarine sediments, Qivitu Peninsula, Baffin Island
Authors: Nelson Alan R.
Published: March 2010

A complex sequence of cyclical marine and glaciomarine lithofacies exposed along the coastal lowlands of the Qivitu Peninsula was deposited during the marine transgressions and regressions that affected this area during repeated glaciation of the region. Multivariate analysis of amino acid ratios measured on shell fragments of the pelecypods Hiatella arctica and Myatruncata in the lithostratigraphic units provides a basis for their chronocorrelation through the use of informal regional aminostratigraphic units termed aminozones. All but the oldest aminozones correspond with particular lithostratigraphic units deposited during transgressive–regressive periods when relative sea level was higher than present sea level. Discriminant analysis shows total amino acid fraction allo/iso ratios from either species are the best overall criteria for assigning a shell sample to a particular aminozone, but free fraction allo/iso ratios are more useful in the younger zones. The distribution of ratios in lithostratigraphic units indicates a large proportion of shell fragments is reworked.Interpretation of all 14C, uranium-series, paleomagnetic, and amino acid data from eastern Baffin Island suggests aminozone 1 is [Formula: see text] years BP, aminozone 2 is [Formula: see text] years BP, aminozone 3 is [Formula: see text] years BP, and aminozone 4 is [Formula: see text] years BP. The extent of isoleucine epimerization in shell samples indicates some aminozones may be of early or pre-Quaternary age.
Transverse folding and superposed deformation, Mount Fisher area, southern Canadian Rocky Mountain thrust and fold belt
Authors: McMechan M. E. , Price R. A.
Published: March 2010

A northeast-facing panel of Middle Proterozoic (Purcell Supergroup) strata occurs beneath Cambrian and Devonian strata along the east side of the Rocky Mountain Trench in the Mount Fisher area. Anomalous northeast-trending folds, faults, and cleavage that formed during Cretaceous–Paleocene deformation occur in this panel in the northern part of the area. The dominant structure in the southern part is the northwest-trending Lizard segment of the (Mesozoic) Hosmer nappe, which folds an older north-trending cleavage that probably formed during the East Kootenay Orogeny (1300–1350 Ma). Thickness and facies variations in Purcell strata and changes in the level of erosion beneath the sub-Devonian unconformity imply that many of the important structural boundaries in the Mount Fisher area and also the normal faults along the southern Rocky Mountain Trench follow the locus of older structures that were active in the Middle Proterozoic and the early Paleozoic.The anomalous northeast-trending structures in the Mount Fisher and adjacent areas formed because the underlying Hosmer thrust developed across a major, pre-Devonian, northwest-facing drape fold, the Dibble Creek monocline. Ramps connecting bedding-glide zones were deflected across the monocline, and strata were gravitationally compressed to form northeast-trending folds, faults, and cleavage as they were displaced up the monocline along the Moyie – Dibble Creek fault.
Isotopic and trace element study of the Loon Lake pluton, Grenville Province, Ontario
Authors: Heaman Larry M. , Shieh Yuch-Ning , McNutt Robert H. , Shaw Denis M.
Published: March 2010

The Loon Lake pluton is a small, reversely zoned pluton with subordinate isolated bodies of diorite and granodiorite gneiss. This pluton is located within the Hastings Basin of the Grenville Province and intrudes the structurally complex Grenville Supergroup.A synthesis of the oxygen and strontium isotopic and trace element data for the monzonite core and quartz monzonite rim indicates that these units are cogenetic but the margin of the pluton has interacted with a CO2–H2O fluid derived from the country rock. This interaction influenced the REE pattern and produced a noticeable enrichment of Rb, 18O, and possibly SiO2 in the rim but did not significantly influence the strontium isotopic systematics. A composite isochron including samples from both units indicates an emplacement age of 1065 ± 13 Ma with an initial strontium ratio of 0.7034 ± 0.0004. Samples from the isolated mafic units indicate an older age and therefore are not interpreted as cogenetic endmembers.The uniform but abnormally high δ18O in the monzonite core and low initial strontium ratio are interpreted to reflect a source composition in the lower crust.
Ichnology of American chalks: the Selma Group (Upper Cretaceous), western Alabama
Authors: Frey Robert W. , Bromley Richard G.
Published: March 2010

Chalk facies within the Selma Group, most of them impure, crop out only in a relatively small area of western Alabama and eastern Mississippi and grade laterally into calcareous terrigenous clastics. Body fossils and skeletal borings (described in a separate paper) are diverse and abundant in some units, especially the impure chalks. Major burrow forms, also distributed unequally among these units, include Chondrites sp., Cylindrichnus pustulosus n. sp., Planolites beverleyensis, Skolithos sp., Teichichnus rectus, Teichichnus zigzag n. sp., Thalassinoides paradoxicus, Thalassinoides suevicus, Trichichnus linearis, Zoophycos sp., and mineralized burrows. Minor forms include Palaeophycus sp., Rosselia spp., and mantled burrows.Characteristic trace fossil distributions especially include the striking dominance of Thalassinoides paradoxicus in chalk hardgrounds of the Arcola Member of the Mooreville Chalk and successive patterns of bioturbation in the lower unnamed member of the Demopolis Chalk. In purer chalks there, major burrow forms exhibit a chronologic sequence of ichnologic events, expressed by (1) cross-cutting relationships among burrows, (2) increased sharpness of younger burrow outlines, and (3) increased contrasts in color and composition of younger burrow fills. The sequence, interpreted to represent differences in depth of burrowing, consistency of the substrate, and type of biogenic activity, proceeds from vague burrow mottles and indistinct Thalassinoides sp., through increasingly distinct Thalassinoides suevicus, Zoophycos sp., and Teichichnus rectus, to sharply defined Teichichnus zigzag and Chondrites sp. Similar relationships, although less conspicuous, are discernible in the Mooreville and Prairie Bluff chalks.
Deglaciation chronology and revegetation in northwestern Ontario
Authors: Björck Svante
Published: March 2010

Along a 420 km transect in northwestern Ontario, Canada, sediments from four lakes were analyzed with respect to lithology, pollen, and macrofossils. Radiocarbon dates show that the region was deglaciated between ca. 11 500 and 8000 years BP, and periods of both rapid ice retreat and readvance influenced the history of Glacial Lake Agassiz. In the south the ice sheet was succeeded by a lengthy interval of park–tundra with stands of spruce, ash, and elm. The ash and elm seem to have disappeared during a suggested cool period (11 100–10 200 years BP). Farther north the park–tundra phase lasted not more than 50–100 years after ca. 10 200 years BP before boreal trees dominated. The climatic change around 10 200 years BP permitted the very rapid migration of spruce, larch, birch, and jack or red pine into northwestern Ontario from northern Minnesota. The migration routes for Pinus strobus (white pine), Alnus rugosa, and A. crispa were divided, however: one from the south (south of Lake Superior) and one from the east-southeast (north of Lake Superior). White pine reached its maximum distribution 6500–6000 years BP, when the limit was probably 150–200 km north of today's. The composition of the boreal forest during the altithermal was only slightly changed, but the influx of presumed prairie pollen reached a peak ca. 8000–7000 years BP. Since then Picea mariana (black spruce) gradually became the dominating tree species.
Geochemical evolution of the Chatham–Grenville stock, Quebec
Authors: Higgins Michael Denis
Published: March 2010

The Chatham–Grenville stock is an anorogenic multiple intrusion that shows a complete gradation from early cumulate and noncumulate syenites to slightly peralkaline granites. It can be divided into four units. Unit 1, the first unit, is a noncumulate syenite with modal quartz less than 5%. Unit 2 has a wide range in composition from cumulate syenites (no modal quartz) to noncumulate syenites and quartz syenites (modal quartz = 20%). Units 3 and 4 are granites with modal quartz up to 25 and 30%, respectively. The parental magma of the whole complex was syenitic. Differentiation occurred as a result of crystal fractionation by filter pressing both at depth and in situ. Ba, Sr, Rb, and Eu abundances and major-element mass-balance calculations show that alkali feldspar, mafic minerals, and apatite were fractionated. At least 79% fractionation is necessary to transform the mean composition of the first unit (1) into the mean composition of the last unit (4). The rare-earth elements, Th, Ta, Hf, and Zr, did not behave in a residual fashion but may have been fractionated in minor accessory phases such as apatite, zircon, monazite, allanite, and xenotime.
Petrology and geochemistry of Cambrian volcanic rocks from the Avalon Zone in New Brunswick
Authors: Greenough John D. , McCutcheon S. R. , Papezik V. S.
Published: March 2010

Lower to Middle Cambrian volcanic rocks occur within the Avalon Zone of southern New Brunswick at Beaver Harbour and in the Long Reach area. The Beaver Harbour rocks are intensely altered, but the major- and trace-element geochemistry indicates that they could be highly evolved (basaltic andesites) within-plate basalts. The mafic flows from the Long Reach area form two chemically and petrologically distinct groups: (1) basalts with feldspar phenocrysts that represent evolved continental tholeiites with some oceanic characteristics; and (2) a group of aphyric basalts showing extremely primitive continental tholeiite compositions, also with oceanic affinities and resembling some rift-related Jurassic basalts on the eastern seaboard. Felsic pyroclastic rocks in the Long Reach area make the suite bimodal. This distribution of rock types supports conclusions from the mafic rocks that the area experienced tension throughout the Early to Middle Cambrian.
Discrete phase space - III: The divergence-free S-matrix elements
Authors: Das A.
Published: March 2010

In the arena of the discrete phase space and continuous time, the theory of S-matrix is formulated. In the special case of quantum electrodynamics (QED), the Feynman rules are precisely developed. These rules in the four-momentum turn out to be identical to the usual QED, except for the vertex function. The new vertex function is given by an infinite series that can only be treated in an asymptotic approximation at the present time. Preliminary approximations prove that the second-order self-energies of a fermion and a photon in the discrete model have convergent improper integrals. In the final section, a sharper asymptotic analysis is employed. It is proved that in case where the number of external photon or fermion lines is at least one, then the S-matrix elements converge in all orders. Moreover, there are no infrared divergences in this formulation.
Gain enhancement in two-stream electromagnetically pumped free electron laser with ion-channel guiding
Authors: Saviz S. , Mehdian H.
Published: March 2010

A theory of two-stream electromagnetic wave-wiggler free-electron lasers (TSEMWFEL) with an ion-channel guiding is proposed and investigated. An analysis of the two-stream steady-state electrons trajectories is obtained by solving the equation of motion in the electromagnetic wave wiggler and ion-channel guiding. The electron trajectories and the small signal gain are derived. Numerical calculations show that there are seven group trajectories rather than the two groups reported for conventional free-electron lasers. The characteristics of the linear-gain and the normalized maximum gain are studied numerically. It was also shown that the normalized gain of groups I and II is decreased and for groups (IV–VII) are increasing by growing [Formula: see text]. Furthermore, it was found that the two-stream with ion-channel field enhances the maximum gain in comparison with that for single beam.
Control of mass concentration of reagents by sound in a gas with nonequilibrium chemical reactions
Authors: Perelomova Anna
Published: March 2010

The weakly nonlinear dynamics of a chemically reacting gas is studied. Nonlinear interaction of acoustic and nonacoustic types of motion are considered. We decompose the base equations using the relationships of the gas-dynamic perturbations specific for every type of motion. The governing equation for the mass fraction of a reagent influenced by dominating sound is derived and discussed. The conclusions concern the equilibrium and nonequilibrium regimes of the chemical reactions.
Stokes’ first problem for an electro-conducting micropolar fluid with thermoelectric properties
Authors: Ezzat Magdy A. , Youssef Hamdy M.
Published: March 2010

This work is related to the flow of an electro-conducting micropolar fluid presenting thermoelectric properties effect in the presence of a magnetic field. The electro-conducting thermofluid equation of heat transfer with one relaxation time is derived. The flow of an electro-conducting micropolar fluid over a plate that is moved suddenly is considered. The governing coupled equations in the frame of the boundary-layer model are applied to Stokes' first problem with heat sources. Laplace-transform and Fourier-transform techniques are used to obtain the solution. The inverses of the Fourier transforms are obtained analytically. The Laplace transforms are obtained using the complex inversion formula of the transform together with Fourier-expansion techniques. Numerical results for the temperature distribution, the velocity, and the microrotation components are represented graphically. Thermoelectric figure-of-merit, Seebeck and Peltier effects on a micropolar fluid are studied.
An exact solution of the Dirac equation for a time-dependent Hamiltonian in 1-1 dimension space-time
Authors: Solomon Dan
Published: March 2010

We find an exact solution to the Dirac equation in 1–1 dimension space-time in the presence of a time-dependent potential that consists of a combination of electric, scalar, and pseudoscalar terms.
SYMMETRY OF DIRAC EQUATION AND CORRESPONDING PHENOMENOLOGY
Authors: KE HONG-WEI , LI ZUO , CHEN JING-LING , DING YI-BING , LI XUE-QIAN
Published: March 2010

It has been suggested that the high symmetries in the Schrödinger equation with the Coulomb or harmonic oscillator potentials may remain in the corresponding relativistic Dirac equation. If the principle is correct, in the Dirac equation the potential should have a form as [Formula: see text] where V(r) is [Formula: see text] for hydrogen atom and κr2 for harmonic oscillator. However, in the case of hydrogen atom, by this combination the spin–orbit coupling term would not exist and it is inconsistent with the observational spectra of hydrogen atom, so that the symmetry of SO(4) must reduce into SU(2). The governing mechanisms QED and QCD which induce potential are vector-like theories, so at the leading order only vector potential exists. However, the higher-order effects may cause a scalar fraction. In this work, we show that for QED, the symmetry restoration is very small and some discussions on the symmetry breaking are made. At the end, we briefly discuss the QCD case and indicate that the situation for QCD is much more complicated and interesting.
ON BARYON NUMBER NONCONSERVATION IN TWO-DIMENSIONAL O(2N+1) QCD
Authors: FRIEDMANN TAMAR
Published: March 2010

We construct a classical dynamical system whose phase space is a certain infinite-dimensional Grassmannian manifold, and propose that it is equivalent to the large N limit of two-dimensional QCD with an O (2N+1) gauge group. In this theory, we find that baryon number is a topological quantity that is conserved only modulo 2. We also relate this theory to the master field approach to matrix models.
GRAVITY IN BRANS–DICKE THEORY WITH BORN–INFELD SCALAR FIELD AND THE PIONEER ANOMALY
Authors: SMOLYAKOV MIKHAIL N.
Published: March 2010

In this paper we discuss a model which can be considered as a generalization of the well-known scalar–tensor Brans–Dicke theory. This model possesses an interesting feature: due to Born–Infeld-type nonlinearity of the scalar field the properties of the interaction between two test bodies depend significantly on their masses. It is shown that the model can be interesting in view of the Pioneer 10, 11 spacecraft anomaly.
PHYSICAL PROPERTIES OF TELLURITE GLASSES PREPARED UNDER DIFFERENT THERMAL HISTORIES
Authors: ARAÚJO E. B. , IDALGO E. , MORAES A. P. A. , FILHO A. G. SOUZA , FILHO J. MENDES
Published: March 2010

Tellurite glasses were prepared with identical 20 Li 2 O -80 TeO 2 nominal compositions but with different thermal histories. Differential scanning calorimetry (DSC), X-ray diffraction (XRD) and Raman spectroscopy techniques were used to understand the effects of the thermal histories on the thermal and structural properties of these glasses. It was observed that investigated properties depend strongly on the thermal histories. DSC results suggested that annealing immediately after quenching at temperatures around the glass transition temperature (Tg) and for longer times is favorable for producing local ordered regions in the glass without necessarily increasing the number of nuclei. XRD results revealed the crystallization of the γ- TeO 2, α- TeO 2 and α- Li 2 Te 2 O 5 phases in both studied glasses. Raman spectroscopy revealed the mestastable character of the γ- TeO 2 crystalline phase, while the α- TeO 2 and α- Li 2 Te 2 O 5 crystalline phases persisted up to the final stages of the in-situ crystallization.
CANNY ALGORITHM, COSMIC STRINGS AND THE COSMIC MICROWAVE BACKGROUND
Authors: DANOS REBECCA J. , BRANDENBERGER ROBERT H.
Published: March 2010

We describe a new code to search for signatures of cosmic strings in cosmic microwave anisotropy maps. The code implements the Canny algorithm, an edge detection algorithm designed to search for the lines of large gradients in maps. Such a gradient signature which is coherent in position-space is produced by cosmic strings via the Kaiser–Stebbins effect. We test the power of our new code to set limits on the tension of the cosmic strings by analyzing simulated data, with and without cosmic strings. We compare maps with a pure Gaussian scale-invariant power spectrum with maps which have a contribution of a distribution of cosmic strings obeying a scaling solution. The maps have angular scale and angular resolution comparable to what current and future ground-based small-scale cosmic microwave anisotropy experiments will achieve. We present tests of the codes, indicate the limits on the string tension which could be set with the current code, and describe various ways to refine the analysis. Our results indicate that when applied to the data of ongoing cosmic microwave experiments such as the South Pole Telescope project, the sensitivity of our method to the presence of cosmic strings will be more than an order of magnitude better than the limits from existing analyses.
THERMODYNAMICS OF VISCOUS DARK ENERGY IN AN RSII BRANEWORLD
Authors: SETARE M. R. , SHEYKHI A.
Published: March 2010

We show that for an RSII braneworld filled with interacting viscous dark energy and dark matter, one can always rewrite the Friedmann equation in the form of the first law of thermodynamics, dE = ThdSh + WdV, at the apparent horizon. In addition, the generalized second law of thermodynamics can be fulfilled in a region enclosed by the apparent horizon on the brane for both constant and time-variable five-dimensional Newton's constant G5. These results hold regardless of the specific form of the dark energy. Our study further supports the belief that in an accelerating universe with spatial curvature, the apparent horizon is a physical boundary from the thermodynamical point of view.
COLLECTIVE BEHAVIORS OF SPIRAL WAVES IN THE NETWORKS OF HODGKIN-HUXLEY NEURONS IN PRESENCE OF CHANNEL NOISE
Authors: MA JUN , ZHANG AI-HUA , TANG JUN , JIN WU-YIN
Published: March 2010

Collective behaviors of spiral waves in the networks of Hodgkin-Huxley neuron are investigated. A stable rotating spiral wave can be developed to occupy the quiescent areas in networks of neurons by selecting appropriate initial values for the variables in the networks of neurons. In our numerical studies, most neurons are quiescent and finite (few) numbers of neurons are selected with different values to form a spiral seed. In this way, neurons communicating are carried by propagating spiral wave to break through the quiescent domains (areas) in networks of neurons. The effect of membrane temperature on the formation of spiral wave is investigated by selecting different fixed membrane temperatures in the networks, and it is found that a spiral wave cannot be developed if the membrane temperature is close to a certain threshold. A quantitative factor of synchronization is defined to measure the statistical properties and collective behaviors of the spiral wave. And a distinct phase transition, which indicates the critical condition for spiral survival, is observed in the sudden changing point of the factors of synchronization curve vs. certain bifurcation parameter. Internal noise is introduced into ion channels (channel noise) with the Langevin method. It is found that a stable rotating spiral wave is developed and the spiral wave is robust to weak channel noise (the membrane patch is not small). The spiral wave can not grow up and the stable rotating spiral wave encounters instability in presence of strong channel noise. Coherence resonance-like behavior is observed in calculating the factors of synchronization in presence of channel noise.
GRAPHICAL REPRESENTATION OF CAUSE-EFFECT RELATIONSHIPS AMONG CHEMICAL PROCESS VARIABLES USING A NEURAL NETWORK APPROACH
Authors: DE ALMEIDA GUSTAVO M. , CARDOSO MARCELO , RENA DANILO C. , PARK SONG W.
Published: March 2010

The extraction of information from tabular data is not a natural task for human beings, which is worse when dealing with high dimensional systems. On the other hand, graphical representations make the understanding easier by exploring the human capacity of processing visual information. Such representations can be used for many purposes, e.g., complex systems structuring which contributes to a better understanding of it. This paper constructs a cause-effect map relating the influence of each input process variable on the steam generated by a boiler. The real case study is based on the operations of a chemical recovery boiler of a Kraft pulp mill in Brazil. The map is obtained by two steps, namely the identification of a neural predictive model for the steam and a study of sensitivity analysis. The numerical results are then depicted in a graphical format using a cause-effect map. This representation highlights the relative importance of the predictor variables to the steam generation. The results, in agreement with the literature, show the higher contribution of the heat released during the fuel burning, and the lower influence of both the fuel temperature and the operating variables associated with the primary level of injection of the combustion air.
RECENT DEVELOPMENTS OF STRUCTURAL VIBRATION CONTROL IN CIVIL ENGINEERING IN CHINA
Authors: HONGNAN LI , LINSHENG HUO
Published: March 2010

In recent years, much attention has been paid to research and development of structural control techniques with particular emphasis on alleviation of wind and seismic response of buildings and bridges in China. Structural control in civil engineering has been developed from the concept into a workable technology and applied into practical engineering structures. The aim of this paper is to review a state-of-the-art of researches and application of structural control in civil engineering in China. It includes the passive control, active control, hybrid control, and semi-active control. Finally, the possible future directions of structural control in civil engineering in China are presented.
STATE-OF-THE-ART IN FAILURE MECHANISM AND DAMAGE CONTROL OF LARGE-SCALE URBAN UNDERGROUND BUILDINGS IN CHINA
Authors: YUAN YONG , CHEN ZHIYI
Published: March 2010

The large-scale construction of underground structures prompts researchers and engineers to reconsider seismic safety of existing and new underground structures against future strong earthquakes. This paper attempts to assess the current state-of-the-art in experimental and analytical researches on large-scale urban underground buildings. Three key issues, which need to be urgently resolved in numerical computation, are also discussed. Finally, necessity and applicability of damage control techniques are explored. The techniques, which are proved to be effective in surface buildings, are expected to update seismic performances of underground structures.
AN EVACUATION PLAN FROM A FIRE FOLLOWING EARTHQUAKE IN A CONGESTED CITY AREA
Authors: KOIKE TAKESHI , KANAMORI TAKANORI , SATO YOHEI
Published: March 2010

This paper describes an evacuation assessment from a fire following disaster when a severe earthquake strikes a congested city area. Probabilistic approach will be taken to simulate the evacuation scenario along all the streets which are crowded with evacuation people, in which the ratio of fire-proof structures, ignition rates from fire gutted houses, and population density are assumed in a probabilistic manner based on the investigation data of the 1994 Northridge and 1995 Kobe earthquakes. This study provides a decision measure on how much fire resistive housing ratio is effective or not to prevent the fire initiation, and also to provide an insight on the disaster prevention strategy on the optimal open space allocations for evacuation.
Logspace Reduction of Directed Reachability for Bounded Genus Graphs to the Planar Case
Authors: Kynčl Jan , Vyskočil Tomáš
Published: March 2010

Directed reachability (or briefly reachability) is the following decision problem: given a directed graph
G
and two of its vertices
s
,
t
, determine whether there is a directed path from
s
to
t
in
G
. Directed reachability is a standard complete problem for the complexity class NL. Planar reachability is an important restricted version of the reachability problem, where the input graph is planar. Planar reachability is hard for L and is contained in NL but is not known to be NL-complete or contained in L. Allender et al. [2009] showed that reachability for graphs embedded on the torus is logspace-reducible to the planar case. We generalize this result to graphs embedded on a fixed surface of arbitrary genus.
Universal Design of Auditory Graphs
Authors: Walker B. N. , Mauney L. M.
Published: March 2010

Determining patterns in data is an important and often difficult task for scientists and students. Unfortunately, graphing and analysis software typically is largely inaccessible to users with vision impairment. Using sound to represent data (i.e., sonification or auditory graphs) can make data analysis more accessible; however, there are few guidelines for designing such displays for maximum effectiveness. One crucial yet understudied design issue is exactly how changes in data (e.g., temperature) are mapped onto changes in sound (e.g., pitch), and how this may depend on the specific user. In this study, magnitude estimation was used to determine preferred data-to-display mappings, polarities, and psychophysical scaling functions relating data values to underlying acoustic parameters (frequency, tempo, or modulation index) for blind and visually impaired listeners. The resulting polarities and scaling functions are compared to previous results with sighted participants. There was general agreement about polarities obtained with the two listener populations, with some notable exceptions. There was also evidence for strong similarities regarding the magnitudes of the slopes of the scaling functions, again with some notable differences. For maximum effectiveness, sonification software designers will need to consider carefully their intended users’ vision abilities. Practical implications and limitations are discussed.
Routing in self-organizing nano-scale irregular networks
Authors: Liu Yang , Dwyer Chris , Lebeck Alvin R.
Published: March 2010

The integration of novel nanotechnologies onto silicon platforms is likely to increase fabrication defects compared with traditional CMOS technologies. Furthermore, the number of nodes connected with these networks makes acquiring a global defect map impractical. As a result, on-chip networks will provide defect tolerance by self-organizing into irregular topologies. In this scenario, simple static routing algorithms based on regular physical topologies, such as meshes, will be inadequate. Additionally, previous routing approaches for irregular networks assume abundant resources and do not apply to this domain of resource-constrained self-organizing nano-scale networks. Consequently, routing algorithms that work in irregular networks with limited resources are needed.

In this article, we explore routing for self-organizing nano-scale irregular networks in the context of a Self-Organizing SIMD Architecture (SOSA). Our approach trades configuration time and a small amount of storage for reduced communication latency. We augment an Euler path-based routing technique for trees to generate static shortest paths between certain pairs of nodes while remaining deadlock free. Simulations of several applications executing on SOSA show our proposed routing algorithm can reduce execution time by 8% to 30%.
Speculative parallelization using software multi-threaded transactions
Authors: Raman Arun , Kim Hanjun , Mason Thomas R. , Jablin Thomas B. , August David I.
Published: March 2010

With the right techniques, multicore architectures may be able to continue the exponential performance trend that elevated the performance of applications of all types for decades. While many scientific programs can be parallelized without speculative techniques, speculative parallelism appears to be the key to continuing this trend for general-purpose applications. Recently-proposed code parallelization techniques, such as those by Bridges et al. and by Thies et al., demonstrate scalable performance on multiple cores by using speculation to divide code into atomic units (transactions) that span multiple threads in order to expose data parallelism. Unfortunately, most software and hardware Thread-Level Speculation (TLS) memory systems and transactional memories are not sufficient because they only support single-threaded atomic units. Multi-threaded Transactions (MTXs) address this problem, but they require expensive hardware support as currently proposed in the literature. This paper proposes a Software MTX (SMTX) system that captures the
applicability
and
performance
of hardware MTX, but on
existing multicore machines
. The SMTX system yields a harmonic mean speedup of 13.36x on native hardware with four 6-core processors (24 cores in total) running speculatively parallelized applications.
Probabilistic job symbiosis modeling for SMT processor scheduling
Authors: Eyerman Stijn , Eeckhout Lieven
Published: March 2010

Symbiotic job scheduling boosts simultaneous multithreading (SMT) processor performance by co-scheduling jobs that have `compatible' demands on the processor's shared resources. Existing approaches however require a sampling phase, evaluate a limited number of possible co-schedules, use heuristics to gauge symbiosis, are rigid in their optimization target, and do not preserve system-level priorities/shares.

This paper proposes probabilistic job symbiosis modeling, which predicts whether jobs will create positive or negative symbiosis when co-scheduled without requiring the co-schedule to be evaluated. The model, which uses per-thread cycle stacks computed through a previously proposed cycle accounting architecture, is simple enough to be used in system software. Probabilistic job symbiosis modeling provides six key innovations over prior work in symbiotic job scheduling: (i) it does not require a sampling phase, (ii) it readjusts the job co-schedule continuously, (iii) it evaluates a large number of possible co-schedules at very low overhead, (iv) it is not driven by heuristics, (v) it can optimize a performance target of interest (e.g., system throughput or job turnaround time), and (vi) it preserves system-level priorities/shares. These innovations make symbiotic job scheduling both practical and effective.

Our experimental evaluation, which assumes a realistic scenario in which jobs come and go, reports an average 16% (and up to 35%) reduction in job turnaround time compared to the previously proposed SOS (sample, optimize, symbios) approach for a two-thread SMT processor, and an average 19% (and up to 45%) reduction in job turnaround time for a four-thread SMT processor.
Request behavior variations
Authors: Shen Kai
Published: March 2010

A large number of user requests execute (often concurrently) within a server system. A single request may exhibit fluctuating hardware characteristics (such as instruction completion rate and on-chip resource usage) over the course of its execution, due to inherent variations in application execution semantics as well as dynamic resource competition on resource-sharing processors like multicores. Understanding such behavior variations can assist fine-grained request modeling and adaptive resource management.

This paper presents operating system management to track request behavior variations online. In addition to metric sample collection during periodic interrupts, we exploit the frequent system calls in server applications to perform low-cost in-kernel sampling. We utilize identified behavior variations to support or enhance request modeling in request classification, anomaly analysis, and online request signature construction. A foundation of our request modeling is the ability to quantify the difference between two requests' time series behaviors. We evaluate several differencing measures and enhance the classic dynamic time warping technique with additional penalties for asynchronous warp steps. Finally, motivated by fluctuating request resource usage and the resulting contention, we implement contention-easing CPU scheduling on multicore platforms and demonstrate its effectiveness in improving the worst-case request performance.

Experiments in this paper are based on five server applications -- Apache web server, TPCC, TPCH, RUBiS online auction benchmark, and a user-content-driven online teaching application called WeBWorK.
ConMem
Authors: Zhang Wei , Sun Chong , Lu Shan
Published: March 2010

Multicore technology is making concurrent programs increasingly pervasive. Unfortunately, it is difficult to deliver reliable concurrent programs, because of the huge and non-deterministic interleaving space. In reality, without the resources to thoroughly check the interleaving space, critical concurrency bugs can slip into production runs and cause failures in the field. Approaches to making the best use of the limited resources and exposing severe concurrency bugs before software release would be desirable.

Unlike previous work that focuses on bugs caused by specific interleavings (e.g., races and atomicity-violations), this paper targets concurrency bugs that result in one type of severe effects: program crashes. Our study of the error-propagation process of realworld concurrency bugs reveals a common pattern (50% in our non-deadlock concurrency bug set) that is highly correlated with program crashes. We call this pattern concurrency-memory bugs: buggy interleavings directly cause memory bugs (NULL-pointer-dereference, dangling-pointer, buffer-overflow, uninitialized-read) on shared memory objects.

Guided by this study, we built ConMem to monitor program execution, analyze memory accesses and synchronizations, and predicatively detect these common and severe concurrency-memory bugs. We also built a validator ConMem-v to automatically prune false positives by enforcing potential bug-triggering interleavings.

We evaluated ConMem using 7 open-source programs with 9 real-world severe concurrency bugs. ConMem detects more tested bugs (8 out of 9 bugs) than a lock-set-based race detector and an unserializable-interleaving detector that detect 4 and 5 bugs respectively, with a false positive rate about one tenth of the compared tools. ConMem-v further prunes out all the false positives. ConMem has reasonable overhead suitable for development usage.
MacroSS
Authors: Hormati Amir H. , Choi Yoonseo , Woh Mark , Kudlur Manjunath , Rabbah Rodric , Mudge Trevor , Mahlke Scott
Published: March 2010

SIMD (Single Instruction, Multiple Data) engines are an essential part of the processors in various computing markets, from servers to the embedded domain. Although SIMD-enabled architectures have the capability of boosting the performance of many application domains by exploiting data-level parallelism, it is very challenging for compilers and also programmers to identify and transform parts of a program that will benefit from a particular SIMD engine. The focus of this paper is on the problem of SIMDization for the growing application domain of streaming. Streaming applications are an ideal solution for targeting multi-core architectures, such as shared/distributed memory systems, tiled architectures, and single-core systems. Since these architectures, in most cases, provide SIMD acceleration units as well, it is highly beneficial to generate SIMD code from streaming programs. Specifically, we introduce MacroSS, which is capable of performing macro-SIMDization on high-level streaming graphs. Macro-SIMDization uses high-level information such as execution rates of actors and communication patterns between them to transform the graph structure, vectorize actors of a streaming program, and generate intermediate code. We also propose low-overhead architectural modifications that accelerate shuffling of data elements between the scalar and vectorized parts of a streaming program. Our experiments show that MacroSS is capable of generating code that, on average, outperforms scalar code compiled with the current state-of-art auto-vectorizing compilers by 54%. Using the low-overhead data shuffling hardware, performance is improved by an additional 8% with less than 1% area overhead.
Flexible architectural support for fine-grain scheduling
Authors: Sanchez Daniel , Yoo Richard M. , Kozyrakis Christos
Published: March 2010

To make efficient use of CMPs with tens to hundreds of cores, it is often necessary to exploit fine-grain parallelism. However, managing tasks of a few thousand instructions is particularly challenging, as the runtime must ensure load balance without compromising locality and introducing small overheads. Software-only schedulers can implement various scheduling algorithms that match the characteristics of different applications and programming models, but suffer significant overheads as they synchronize and communicate task information over the deep cache hierarchy of a large-scale CMP. To reduce these costs, hardware-only schedulers like Carbon, which implement task queuing and scheduling in hardware, have been proposed. However, a hardware-only solution fixes the scheduling algorithm and leaves no room for other uses of the custom hardware.

This paper presents a combined hardware-software approach to build fine-grain schedulers that retain the flexibility of software schedulers while being as fast and scalable as hardware ones. We propose asynchronous direct messages (ADM), a simple architectural extension that provides direct exchange of asynchronous, short messages between threads in the CMP without going through the memory hierarchy. ADM is sufficient to implement a family of novel, software-mostly schedulers that rely on low-overhead messaging to efficiently coordinate scheduling and transfer task information. These schedulers match and often exceed the performance and scalability of Carbon when using the same scheduling algorithm. When the ADM runtime tailors its scheduling algorithm to application characteristics, it outperforms Carbon by up to 70%.
Technology for developing regions
Authors: Brewer Eric A.
Published: March 2010

The historic focus of development has rightfully been on macroeconomics and good governance, but technology has an increasingly large role to play. In this talk, I review several novel technologies that we have deployed in India and Africa, and discuss the challenges and opportunities of this new subfield of EECS research. Working with the Aravind Eye Hospital, we are currently supporting doctor / patient videoconferencing in 30+ rural villages; more than 25,000 people have had their blindness cured due to these exams.

Although Moore's Law has led to great cost reductions and thus enabled new technologies, we have reached essentially the low point for cost: the computing is essentially free compared to the rest of the system. The premium is thus on a combination of 1) deeper integration (fewer compo-nents), 2) shared usage models (even phones are shared), and 3) lower operating costs in terms of power and connectivity.
Dynamically replicated memory
Authors: Ipek Engin , Condit Jeremy , Nightingale Edmund B. , Burger Doug , Moscibroda Thomas
Published: March 2010

DRAM is facing severe scalability challenges in sub-45nm tech- nology nodes due to precise charge placement and sensing hur- dles in deep-submicron geometries. Resistive memories, such as phase-change memory (PCM), already scale well beyond DRAM and are a promising DRAM replacement. Unfortunately, PCM is write-limited, and current approaches to managing writes must de- commission pages of PCM when the first bit fails.

This paper presents
dynamically replicated memory
(DRM), the first hardware and operating system interface designed for PCM that allows
continued operation through graceful degradation
when hard faults occur. DRM reuses memory pages that con- tain hard faults by dynamically forming pairs of complementary pages that act as a single page of storage. No changes are required to the processor cores, the cache hierarchy, or the operating sys- tem's page tables. By changing the memory controller, the TLBs, and the operating system to be DRM-aware, we can improve the lifetime of PCM by up to 40x over conventional error-detection techniques.
Overlay routing architectures for massively multiuser virtual environments
Authors: Hariri Behnoosh , Alavi Mohammad Hossein , Pakravan Mohammad Reza , Shirmohammadi Shervin
Published: March 2010

Massively Multiuser Virtual Environments (MMVE) are network applications that simulate the experience of realtime interaction among multiple users distributed all over the internet. In order to share the common sense of time and place, multiple entities interacting in the shared virtual environment must be aware of the modifications or interactions within the shared environment. This is achieved through the distribution of update messages. As the number of users and entities increases, there is a considerable increase in the amount of update messages exchanged among the users and entities. Supporting the large of update messages, especially in massive environments, is one of the most important challenges in the design of MMVEs. The use of a distributed architecture allowing users to handle the traffic among each other in a peer to peer (P2P) fashion is one solution to this problem. However, such solution must in turn deal with a variety of challenges related to the noncentralized nature of the protocol.
Architectural challenges and solutions for peer-to-peer massively multiplayer online games
Authors: Ahmed Dewan Tanvir , Shirmohammadi Shervin
Published: March 2010

Massively Multiplayer Online Games (MMOG), now supporting millions of simultaneous participants on a regular basis, have become a significant contributor in human-to-human communications. While originally designed for games, they have now moved into serious realms of socialization, business, commerce, scientific experimentation, and others. As more and more people participate in these massive environments, the underlying infrastructure is starting to exhibit shortcomings that limit the progress, practicality, and applicability of MMOGs. This thesis explores various architectural challenges inherent in MMOGs and offers effective solutions in the context of a hybrid model. The key objective of this hybrid model, realized in a Massively Multiuser VIrtual Simulation Architecture (MM-VISA), is to form a stable and scalable collaboration platform that economically combines the resources of both servers and player peers, incorporating the advantages of a centralized architecture and a scalable Peer-to-Peer distributed system, which in turn leads to improved support for the participating masses.
Adaptive modeling and distribution of large natural scenes
Authors: Mondet Sebastien , Paulin Mathias , Morin Geraldine , Grigoras Romulus , Ooi Wei Tsang , Hahmann Stefanie , Steinbach Eckehard
Published: March 2010

This thesis deals with the modeling and the interactive streaming of large natural 3D scenes. We aim at providing techniques to allow the remote walkthrough of users in a natural 3D scene ensuring botanical coherency and interactivity.