bluuebunny/crossref_metadata_2025 huggingface dataset:
Age-class distribution and spatial patterns in an old-growth hemlock–hardwood forest
Authors: Frelich Lee E. , Graumlich Lisa J.
Published: January 2008

The frequency of canopy disturbance over the past 150 years was reconstructed on a 5-ha study area dominated by a patchy mosaic of old-growth sugar maple (Acersaccharum Marsh.) and eastern hemlock (Tsugacanadensis (L.) Carr.) forest in the Sylvania Wilderness Area in western Upper Michigan. The study area was divided into a 10-m grid system and one tree was cored near the center of each grid cell so that the spatial patterns of tree cohorts could be examined. The canopy turnover rate, averaged over all species and 150 years was 5.4% per decade, with a corresponding canopy residence time of 186 years. Canopy-residence times do not vary much between sugar maple (170 years) and hemlock (167 years), but yellow birch has a much longer canopy-residence time (232 years). Canopy-residence times calculated for individual decades over the last 150 years varied from 81 to 556 years. The spatial pattern of gaps of various ages is caused by disturbances in light intensity (2–12% canopy removal) that occur nearly every decade, each of which creates several to many small gaps scattered across the study area. As a result, the study area has a fine-grained random spatial mixture of age-classes at all distance classes from 5 m to >100 m. This mixture is stable throughout the mesic forest in the study area. None of the cohorts resulting from disturbance correspond spatially to patches dominated by either hemlock or sugar maple. Apparently, the dynamics of patch formation by gap-creating disturbances operate independently from the dynamics of the much larger mono-dominant patches. In forests such as the northern hardwood–hemlock type, where several tree lifetimes pass between any two large-scale catastrophic disturbances, spatial and temporal stability of the patch-dynamic processes (quasi equilibrium) may exist for periods of several decades in areas of <1 ha, and several thousand years for landscapes >10 000 ha in size.
Genetic parameters of growth characters in Salixviminalis grown in Sweden
Authors: Rönnberg-Wästljung Ann Christin , Gullberg Urban , Nilsson Christina
Published: January 2008

Forty families of Salixviminalis L. from an eight by eight factorial crossing were planted in contrasting environments to estimate genetic additive, dominance, and epistatic variances and to estimate the impact of genotype–environment interaction. From each family, 14 seed plants were vegetatively propagated. The material was planted in two contrasting soils, heavy clay soil and sandy soil, and in two contrasting nutrient availabilities, high and low. The nutrient experiment was harvested annually for 3 years. The clay–sand experiment was harvested in the 1st, 4th, and 6th year. Height, diameter, weight, and number of shoots were measured. Additive genetic variance was found, but there were large standard deviations in many of the estimates, especially in the nutrient experiment. Dominance and epistatic variances of greater significance were found for weight characters in the clay–sand experiment. Narrow-sense heritability estimates varied, with the highest estimate being 0.34. Genotype–environment interaction seems to be of greatest importance in the establishment years in the soil contrast but of increasing importance in the nutrient contrast. Breeding strategies in connection with these findings are discussed.
Valdensiniaheterodoxa (Sclerotiniaceae) in the United States
Authors: Norvell Lorelei L. , Redhead Scott A.
Published: January 2008

The leaf-spot pathogen Valdensiniaheterodoxa Peyronel is reported for the first time from the United States (Idaho, Washington, and Oregon), based on the recovery of the anamorph. Scanning electron micrographs illustrate anamorphic propagules collected from economically significant ericaceous hosts Gaultheriashallon Pursh, Vacciniumalaskaense Howell, and Vacciniummembranaceum Douglas.
Riparian edge effects on boreal balsam fir bird communities
Authors: Larue Pierre , Bélanger Louis , Huot Jean
Published: January 2008

Riparian forests are often identified as prime habitat for wildlife because of the presence of particular plant communities and edges creating a highly developed and diversified vegetation structure. However, in the northeastern boreal forests of Canada, where narrow land–water ecotones with abrupt edges are quite common, the relative habitat value of riparian forests remains to be demonstrated. We compared bird communities of eight pairs of riparian and nonriparian plots, similar in vegetation structure and composition, to verify the relative value for breeding birds of typical coniferous riparian forest stands of the southern boreal region of eastern Quebec. Bird abundance (P = 0.02), richness (P = 0.03), and diversity (P = 0.02) were significantly higher in the riparian stands, where the spatial sequence of three distinct habitats (a balsam fir (Abiesbalsamea (L.) Mill.)–northern white cedar (Thujaoccidentalis L.) forest, a narrow alder (Alnusrugosa (Du Roi) Spreng.) - grass wetland, and water) created high horizontal vegetation diversity. In riparian stands median bird richness and density were, respectively, 23.5 species and 437.5 territories/km2 compared with 19.0 species and 348.2 territories/km2 for interior stands. Nine species were observed exclusively in riparian plots. In addition to the species usually found in the studied nonriparian forests, the riparian plots were used by species typically related to the water edge such as the Northern Waterthrush (Seiurusnoveboracensis Gmelin) and Rusty Blackbird (Euphaguscarolinus Miiller) as well as species associated with the shrub and grass wetland such as the American Robin (Turdusmigratorius L.), the Veery (Catharusfuscescens Stephens), and the Common Yellowthroat (Geothlypistrichas L.). The shrub-foraging guild showed higher abundance in riparian stands. The tree-foraging and tree-bole foraging guilds, however, were comparable in both groups of stands. In this study, the natural conditions prevailing along he riparian sites appeared mostly positive for the breeding-bird community; it created what is perceived as being an "edge effect." The edge effect can be defined, in this case, as being the additional density and number of species induced by the added horizontal vegetation diversity created by the close association of three extremely different ecosystems: a forest stand, an aquatic ecosystem, and a narrow but distinct shrub-grass wetland. This also confirms the necessity of distinguishing natural edges that are permanent features of the landscape from induced edges created by human activity.
Spacing and provenance effects on the performance of shore pine (Pinus contorta var. contorta): 20-year test results
Authors: Xie C.Y. , Ying C.C. , Johnstone W.D.
Published: January 2008

Spacing and provenance effects on the performance of shore pine (Pinuscontorta var. contorta) at a frost-prone site in coastal British Columbia were investigated with respect to mortality, growth, stem defects, and disease and insect damages in a trial with six seed sources that were assigned to seven spacing regimes from 749 to 2990 stems per hectare. Twenty-year test results indicate that mortality was low (2.3% on average) and not significantly influenced by spacing. However, spacing effects on the other traits were significant. Increasing planting density reduced the proportion of stem defected and disease- and insect-damaged trees, slowed diameter and stem volume growth of individuals, and stimulated height growth. Height growth responded to planting density earlier than diameter growth, but diameter growth became more affected as trees grew. The total volume per hectare increases with planting density, but the rate of increase declined as the test proceeded. Response to planting density was homogeneous among provenances with respect to all the traits investigated. However, large and significant regional and provenance differences in mortality, growth, and disease and insect susceptibility were detected. Northern and outer coast provenances demonstrated higher mortality, slower growth, and larger proportions of disease- and insect-damaged trees. Clearly, determining appropriate spacing levels and selecting suitable seed sources are both important for the success of reforestation with shore pine at difficult sites.
Six-year response of red oak seedlings planted under a shelterwood in central Ontario
Authors: Gordon Andrew M. , Simpson James A. , Williams Peter A.
Published: January 2008

This study investigated the potential for underplanting 1 + 0 and 1 + 1 northern red oak (Quercusrubra L.) in conjunction with a two-cut shelterwood harvest of a low-quality, ridgetop, tolerant hardwood stand in central Ontario. Growth patterns were followed for 6 years; herbicide (glyphosate) application and prescribed fire (two burns, 3 years apart) were used as competition control measures in an experimental design that tested all possible combinations of stock type, competition control, and clipping 2 years after planting. Six years after outplanting the mean height attained across all treatments for 1 + 0 stock was 76 cm and for 1 + 1 stock, almost 90 cm. Depending upon treatment, some individuals were almost 3 m tall. In the presence of heavy deer (Odocoileusvirginianus Zimmerman) browsing, competition control of any type does not appear to be warranted. Clipping also does not appear to be advantageous. We can speculate that competition control made seedlings more susceptible to browsing by deer or damage by heavy snow and ice accumulation. The competitive ability of red oak on these sites is such that it will respond well to even late release from normal competition resulting from overstory disturbance (i.e., control treatment). The general technique for establishment of oak in this manner appears to be logical for these site conditions, but further investigation is necessary to address the direct impact of browsing pressure on seedling growth and the potential for similar silvicultural prescriptions on more marginal oak sites.
Capacity changes in U.S. particleboard, southern pine plywood, and oriented strandboard industries
Authors: Spelter Henry
Published: January 2008

An industry's supply response can be decomposed into tactical (short-run) and strategic (long-run) components. The strategic component, dealing with investments in new capacity, determines the evolution of an industry and its ability to meet changing market demands. A decisive factor affecting capacity investment is the profitability of the commodity produced in relation to the cost of the equipment needed to make it. This concept is related to a theory of investment embodied in the concept of "q" developed by J. Tobin, which suggests that the ratio between the market value of an industry and the replacement cost of capital influences decisions to invest. The results developed here suggest that the theory works well for oriented strandboard, southern pine plywood, and particleboard industries. However, adjustments must be made to the empirical formula to take into account lags between the price stimulus and investment response and the difference in growth rates during the early phases of an industry's life compared with the more mature phases.
Nutrient supply and declines in leaf area and production in lodgepoie pine
Authors: Binkley Dan , Smith F.W. , Son Y.
Published: January 2008

In southeastern Wyoming, stand leaf area and production of lodgepoie pine (Pinuscontorta Dougl.) peak early in stand development and then decline. We tested the hypothesis that these declines followed decreasing nutrient supply and increasing nutrient limitation in older forests. Single-tree fertilization plots in 28 stands were used to test for nutrient limitation with stand age and density. Younger stands (<40 year old) had higher net nitrification and mineralization. These stands showed no significant response to fertilization in either needle fascicle weight or basal area growth. All older age-classes responded strongly in both fascicle weight and basal area growth. Foliar analysis indicated that N, P, and K all limited growth in older stands, but basal area increments indicated maximum responses to N alone. We conclude that increasing nutrient limitation in older stands probably accounts for at least part of the decline in stand leaf area and growth. Such declines may be responsive to a range of management activities that improve or impair stand nutrition.
Growth, allocation, and morphological responses of Betulapubescens and Betulapendula to shade in developing Scots pine stands
Authors: Messier Christian , Puttonen Pasi
Published: January 2008

The growth, biomass allocation, crown architecture, and leaf morphology of 50 to 200 cm tall Betulapubescens Ehrh. and Betulapendula Roth seedlings growing under eight Scots pine (Pinussylvestris L.) stands varying in age from 7 to 105 years were studied in southern Finland. The main objective of the study was to assess the degree of morphological plasticity of birch in response to understory conditions in stands of varying structure. In each of these stands, the light, water, and nutrient availability were measured. No clear trend in nutrient and water availability was found from the 7- to 105-year-old stands. Light availability decreased from the 7-year-old stands (45% and 82% of full sunlight in nongap and gap locations, respectively) to the 20-year-old stands (5% and 12% of full sunlight), and then increased to the mature stands (21% and 26% of full sunlight). Relative branch growth rate and height increment decreased with increasing shade. The ratios of leaf area to branch length and to branch weight did not vary significantly among the eight stands. The ratios of height to diameter and fine-root biomass to leaf biomass were the highest under the most shaded stands (20-year-old). Increase in shading decreased leaf thickness and increased specific leaf weight. No major differences were found in any of the growth parameters measured between the two birch species, indicating that they do not differ in their juvenile stage. These results indicate that these two birch species have relatively little morphological plasticity in response to shade. They appear to be able to persist in shade by minimizing carbon demand for growth and by modifying leaf morphology to presumably optimize photosynthesis.
A transaction evidence based estimate of the stumpage value of some southern Ontario forest species
Authors: Nautiyal Jagdish C. , Kant Shashi , Williams Jeremy S.
Published: January 2008

Most of the timber harvested in southern Ontario is sold in an open market. Sales are mainly conducted on mixed-species woodlots and include a range of timber qualities. An econometric model based on the transaction evidence approach and 506 sales data from 1983 to 1993 is developed to estimate the stumpage value of a stand as well as species components most important in determining value. Volume of timber of different species put on sale in a lot was found to be the prime determinant of sale value. For some species the product of average tree size and volume sold turned out to be influential. Per cubic metre value of standing timber was found to generally increase with tree size, but the nature of the relationship was not clearly identifiable. Ash was found to be the most valuable hardwood in southern Ontario. Ownership was a significant determinant of value, privately owned timber fetching much higher value than that on public lands. This may be due to difference in size of Trees on the two types of land. Site characteristics such as slope, underbrush, and distance from mills did not appear to be important in determining values. The reason most probably was that high per cubic metre values commanded by hardwoods rendered site differences and transportation costs in a well-roaded region relatively insignificant. Stand quality might have been an important factor, but poor data on it did not permit any useful analysis.
Growth response of red spruce after known periods of winter injury
Authors: Tobi Donald R. , Bergdahl Dale R. , Wargo Philip M.
Published: January 2008

Winter injury occurred region wide on red spruce (Picearubens Sarg.) during the winters of 1981, 1984, 1989, and 1993, affecting (primarily) needles that were produced during the growing seasons of 1980, 1983, 1988, and 1992, respectively. Red spruce trees growing in four plots, one each above and below cloud base on windward and leeward sides of Whiteface Mountain, Wilmington, N.Y., were evaluated to determine their health classification and growth characteristics in response to winter injury. When needle weight was compared between adjacent years, it was consistently greater on 1981, 1984, and 1989 internodes than on the preceding year's internodes, which were known to be affected by winter injury. When similar comparisons were made on bole growth, basal area increment consistently decreased the growing season immediately after winter injury. The decrease was significant for all health classes on both windward and leeward aspects in 1981. Historical tree-ring records dating back 100 years also showed a reduction in basal area increment associated with years of reported winter injury. Internodal length also decreased in response to winter injury. This decrease was consistent and generally significant in 1983 and 1986, each 2 years after winter injury events. Radial growth reduction in the year of, and internode growth reduction 2 years after, winter injury suggests specific growth processes associated with specific foliage.
FLOP INVARIANCE OF THE TOPOLOGICAL VERTEX
Authors: KONISHI YUKIKO , MINABE SATOSHI
Published: January 2008

We prove transformation formulae for generating functions of Gromov–Witten invariants on general toric Calabi–Yau threefolds under flops. Our proof is based on a combinatorial identity on the topological vertex and analysis of fans of toric Calabi–Yau threefolds.
MONOIDS, EMBEDDING FUNCTORS AND QUANTUM GROUPS
Authors: MÜGER MICHAEL , TUSET LARS
Published: January 2008

We show that the left regular representation πl of a discrete quantum group (A, Δ) has the absorbing property and forms a monoid [Formula: see text] in the representation category Rep (A, Δ).

Next we show that an absorbing monoid in an abstract tensor *-category [Formula: see text] gives rise to an embedding functor (or fiber functor) [Formula: see text], and we identify conditions on the monoid, satisfied by [Formula: see text], implying that E is *-preserving.

As is well-known, from an embedding functor [Formula: see text] the generalized Tannaka theorem produces a discrete quantum group (A, Δ) such that [Formula: see text]. Thus, for a C*-tensor category [Formula: see text] with conjugates and irreducible unit the following are equivalent: (1) [Formula: see text] is equivalent to the representation category of a discrete quantum group (A, Δ), (2) [Formula: see text] admits an absorbing monoid, (3) there exists a *-preserving embedding functor [Formula: see text].
VERTEX-ALGEBRAIC STRUCTURE OF THE PRINCIPAL SUBSPACES OF CERTAIN $A_{1}^{(1)}$-MODULES, I: LEVEL ONE CASE
Authors: CALINESCU C. , LEPOWSKY J. , MILAS A.
Published: January 2008

This is the first in a series of papers in which we study vertex-algebraic structure of Feigin–Stoyanovsky's principal subspaces associated to standard modules for both untwisted and twisted affine Lie algebras. A key idea is to prove suitable presentations of principal subspaces, without using bases or even "small" spanning sets of these spaces. In this paper, we prove presentations of the principal subspaces of the basic [Formula: see text]-modules. These convenient presentations were previously used in work of Capparelli–Lepowsky–Milas for the purpose of obtaining the classical Rogers–Ramanujan recursion for the graded dimensions of the principal subspaces.
COMBINATORIAL DEHN–LICKORISH TWISTS AND FRAMED LINK PRESENTATIONS OF 3-MANIFOLDS REVISITED
Authors: LINS SÓSTENES
Published: January 2008

From a pseudo-triangulation with n tetrahedra T of an arbitrary closed orientable connected 3-manifold (for short, a 3D-space) M3, we present a gem J′, inducing 𝕊3, with the following characteristics: (a) its number of vertices is O(n); (b) it has a set of p pairwise disjoint couples of vertices {ui, vi}, each named a twistor; (c) in the dual (J′)⋆ of J′ a twistor becomes a pair of tetrahedra with an opposite pair of edges in common, and it is named a hinge; (d) in any embedding of (J′)⋆ ⊂ 𝕊3, the ∊-neighborhood of each hinge is a solid torus; (e) these p solid tori are pairwise disjoint; (f) each twistor contains the precise description on how to perform a specific surgery based in a Denh–Lickorish twist on the solid torus corresponding to it; (g) performing all these p surgeries (at the level of the dual gems) we produce a gem G′ with |G′| = M3; (h) in G′ each such surgery is accomplished by the interchange of a pair of neighbors in each pair of vertices: in particular, |V(G′) = |V(J′)|.

This is a new proof, based on a linear polynomial algorithm, of the classical theorem of Wallace (1960) and Lickorish (1962) that every 3D-space has a framed link presentation in 𝕊3 and opens the way for an algorithmic method to actually obtaining the link by an O(n2)-algorithm. Actually this has been done and awaits a proper implentation.
SUPERCONTINUUM CARS TWEEZERS
Authors: SHI KEBIN , LI PENG , LIU ZHIWEN
Published: January 2008

In this paper, we review our recent work on broadband coherent anti-Stokes Raman scattering (CARS) spectroscopy in supercontinuum optical trap.
POLARIZED SPECTRA OF AMPLIFIED SPONTANEOUS EMISSION AND GAIN FOR GLYCERIN SOLUTIONS OF DYE RHODAMINE-640
Authors: BLINOV L. M. , CIPPARRONE G. , LAZAREV V. V. , PAGLIUSI P. , RUGIERO T. , UMANSKII B. A.
Published: January 2008

The polarized spectra of the intensity and gain of the amplified spontaneous emission (ASE) have been measured for two glycerin solutions of a laser dye Rhodamine-640 (RhA and RhB with concentrations of 3 × 10-4 and 3 × 10-3 M/L, respectively). The solutions were pumped by the linearly polarized light. The ASE polarization ratio r strongly depends on the pump pulse energy, which is continuously increasing up to one for RhA and saturating at the level of r ≈ 0.8 for RhB. The gain spectra have been measured by variation of the amplification length for ASE. With increasing pump beam energy, the maximum gain continuously grows for RhA and saturates for RhB, reaching the values of 14–15 and 6 cm-1 for both materials for the polarization parallel to the pump beam polarization. At a particular spectral point, the gain coefficient has also been measured by the direct amplification of the probe beam of a microlaser on a cholesteric liquid crystal.
FOUR-WAVE MIXING IN LEFT-HANDED MATERIALS
Authors: GAO SHIMING , HE SAILING
Published: January 2008

The four-wave mixing (FWM) effect in a so-called left-handed material (LHM) with a third-order nonlinear response is studied. The theoretical models for the wavelength conversion (WC) and parametric amplification (PA) based on the FWM in the LHM are established when the signal falls in the frequency range of backward or forward wave. Analytical formulas for the WC efficiency and PA gain are derived. The influences of the pump powers, the phase mismatch, and the interaction length on the performances of the WC and PA are analyzed. The phase-match dependence of the performance is reduced by carefully controlling the pump powers.
Foveated gaze-contingent displays for peripheral LOD management, 3D visualization, and stereo imaging
Authors: Duchowski Andrew T. , Çöltekin Arzu
Published: January 2008

Advancements in graphics hardware have allowed development of hardware-accelerated imaging displays. This article reviews techniques for real-time simulation of arbitrary visual fields over still images and video. The goal is to provide the vision sciences and perceptual graphics communities techniques for the investigation of fundamental processes of visual perception. Classic gaze-contingent displays used for these purposes are reviewed and for the first time a pixel shader is introduced for display of a high-resolution window over peripherally degraded stimulus. The pixel shader advances current state-of-the-art by allowing real-time processing of still or streamed images, obviating the need for preprocessing or storage.
How late can you update gaze-contingent multiresolutional displays without detection?
Authors: Loschky Lester C. , Wolverton Gary S.
Published: January 2008

This study investigated perceptual disruptions in gaze-contingent multiresolutional displays (GCMRDs) due to delays in updating the center of highest resolution after an eye movement. GCMRDs can be used to save processing resources and transmission bandwidth in many types of single-user display applications, such as virtual reality, video-telephony, simulators, and remote piloting. The current study found that image update delays as late as 60 ms after an eye movement did not significantly increase the detectability of image blur and/or motion transients due to the update. This is good news for designers of GCMRDs, since 60 ms is ample time to update many GCMRDs after an eye movement without disrupting perception. The study also found that longer eye movements led to greater blur and/or transient detection due to moving the eyes further into the low-resolution periphery, effectively reducing the image resolution at fixation prior to the update. In GCMRD applications where longer saccades are more likely (e.g., displays with relatively large distances between objects), this problem could be overcome by increasing the size of the region of highest resolution.
An assessment of eye-gaze potential within immersive virtual environments
Authors: Murray Norman , Roberts Dave , Steed Anthony , Sharkey Paul , Dickerson Paul , Rae John
Published: January 2008

In collaborative situations, eye gaze is a critical element of behavior which supports and fulfills many activities and roles. In current computer-supported collaboration systems, eye gaze is poorly supported. Even in a state-of-the-art video conferencing system such as the access grid, although one can see the face of the user, much of the communicative power of eye gaze is lost. This article gives an overview of some preliminary work that looks towards integrating eye gaze into an immersive collaborative virtual environment and assessing the impact that this would have on interaction between the users of such a system. Three experiments were conducted to assess the efficacy of eye gaze within immersive virtual environments. In each experiment, subjects observed on a large screen the eye-gaze behavior of an avatar. The eye-gaze behavior of that avatar had previously been recorded from a user with the use of a head-mounted eye tracker. The first experiment was conducted to assess the difference between users' abilities to judge what objects an avatar is looking at with only head gaze being viewed and also with eye- and head-gaze data being displayed. The results from the experiment show that eye gaze is of vital importance to the subjects, correctly identifying what a person is looking at in an immersive virtual environment. The second experiment examined whether a monocular or binocular eye-tracker would be required. This was examined by testing subjects' ability to identify where an avatar was looking from their eye direction alone, or by eye direction combined with convergence. This experiment showed that convergence had a significant impact on the subjects' ability to identify where the avatar was looking. The final experiment looked at the effects of stereo and mono-viewing of the scene, with the subjects being asked to identify where the avatar was looking. This experiment showed that there was no difference in the subjects' ability to detect where the avatar was gazing. This is followed by a description of how the eye-tracking system has been integrated into an immersive collaborative virtual environment and some preliminary results from the use of such a system.
The conductor interaction method
Authors: Rachovides Dorothy , Walkerdine James , Phillips Peter
Published: January 2008

Computers have increasingly become part of our everyday lives, with many activities either involving their direct use or being supported by one. This has prompted research into developing methods and mechanisms to assist humans in interacting with computers (human-computer interaction, or HCI). A number of HCI techniques have been developed over the years, some of which are quite old but continue to be used, and some more recent and still evolving. Many of these interaction techniques, however, are not natural in their use and typically require the user to learn a new means of interaction. Inconsistencies within these techniques and the restrictions they impose on user creativity can also make such interaction techniques difficult to use, especially for novice users.

This article proposes an alternative interaction method, the conductor interaction method (CIM), which aims to provide a more natural and easier-to-learn interaction technique. This novel interaction method extends existing HCI methods by drawing upon techniques found in human-human interaction. It is argued that the use of a two-phased multimodal interaction mechanism, using gaze for selection and gesture for manipulation, incorporated within a metaphor-based environment, can provide a viable alternative for interacting with a computer (especially for novice users). Both the model and an implementation of the CIM within a system are presented in this article. This system formed the basis of a number of user studies that have been performed to assess the effectiveness of the CIM, the findings of which are discussed in this work.
An adaptive approach to accelerated evaluation of highly available services
Authors: Hsu Chih-Chieh , Devetsikiotis Michael
Published: January 2008

We motivate and describe improved fast simulation techniques for the accelerated performance evaluation of highly available services. In systems that provide such services, service unavailability events are rare due to a low component failure rate or high resource capacity. Using traditional Monte Carlo simulation to evaluate such services requires a large amount of runtime. Importance sampling (IS) has been applied to certain instances of such systems, focusing on single-class and/or homogeneous resource demands. In this article, we formulate highly available services as multiresource losstype systems, and we present two IS methods for fast simulation, extending to multiple classes and nonhomogeneous resource demands. First, for the cases in which component failure rates are small, we prove that
static
IS using the Standard Clock (S-ISSC) method exhibits the bounded relative error (BRE) property. Second, for estimating failure probabilities due to large capacity or fast service in systems that have nonrare component failure rates, we propose adaptive ISSC (A-ISSC), which estimates the relative probability of reaching each possible state of system failure in every step of the simulation. Using A-ISSC, IS methods which are proven to be efficient can be extended to
multidimensional
cases, while still retaining a very favorable performance, as supported by our validation experiments.
Adaptive Newton-based multivariate smoothed functional algorithms for simulation optimization
Authors: Bhatnagar Shalabh
Published: January 2008

In this article, we present three smoothed functional (SF) algorithms for simulation optimization. While one of these estimates only the gradient by using a finite difference approximation with two parallel simulations, the other two are adaptive Newton-based stochastic approximation algorithms that estimate both the gradient and Hessian. One of the Newton-based algorithms uses only one simulation and has a one-sided estimate in both the gradient and Hessian, while the other uses two-sided estimates in both quantities and requires two simulations. For obtaining gradient and Hessian estimates, we perturb each parameter component randomly using independent and identically distributed (i.i.d) Gaussian random variates.

The earlier SF algorithms in the literature only estimate the gradient of the objective function. Using similar techniques, we derive two unbiased SF-based estimators for the Hessian and develop suitable three-timescale stochastic approximation procedures for simulation optimization. We present a detailed convergence analysis of our algorithms and show numerical experiments with parameters of dimension 50 on a setting involving a network of
M
/
G
/1 queues with feedback. We compare the performance of our algorithms with related algorithms in the literature. While our two-simulation Newton-based algorithm shows the best results overall, our one-simulation algorithm shows better performance compared to other one-simulation algorithms.
Sample-based estimation of correlation ratio with polynomial approximation
Authors: Lewandowski Daniel , Cooke Roger M. , Tebbens Radboud J. Duintjer
Published: January 2008

Sensitivity analysis has become a natural step in the uncertainty analysis framework. As there is no general sensitivity measure that would capture all information on impact of input factors on model output, analysts tend to combine various measures to obtain a broader image of interactions between different modes. This article concentrates on the correlation ratio, demonstrates methods for calculating this quantity efficiently and accurately, and compares the results. A new method inspired by artificial intelligence techniques emerges as outperforming the familiar methods.
Development of a simulation model of colorectal cancer
Authors: Roberts Stephen , Wang Lijun , Klein Robert , Ness Reid , Dittus Robert
Published: January 2008

Colorectal cancer (CRC) is deadly if not found early. Any protocols developed for screening and surveillance and any policy decisions regarding the availability of CRC resources should consider the nature of the disease and its impact over time on costs and quality-adjusted life years in a population. Simulation models can provide a flexible representation needed for such analysis; however, the development of a credible simulation model of the natural history of CRC is hindered by limited data and incomplete knowledge. To accommodate the extensive modeling and remodeling required to produce a credible model, we created an object-oriented simulation platform driven by a model-independent database within the .NET environment. The object-oriented structure not only encapsulated the needs of a simulation replication but created an extensible framework for specialization of the CRC components. This robust framework allowed development to focus modeling on the CRC events and their event relationships, conveniently facilitating extensive revision during model construction. As a second-generation CRC modeling activity, this model development benefited from prior experience with data sources and modeling difficulties. A graphical user interface makes the model accessible by displaying existing scenarios, showing input variables and their values, and permitting the creation of new scenarios and changes to its input. Output from the simulation is captured in familiar tabbed worksheets and stored in the database. The eventual CRC model was conceptualized through a series of assumptions that conformed to beliefs and data regarding the natural history of CRC. Throughout the development cycle, extensive verification and validation calibrated the model. The result is a simulation model that characterizes the natural history of CRC with sufficient accuracy to provide an effective means of evaluating numerous issues regarding the burden of this disease on individuals and society. Generalizations from this study are offered regarding the use of discrete-event simulation in disease modeling and medical decision making.
Exploiting synchronous and asynchronous DVS for feedback EDF scheduling on an embedded platform
Authors: Zhu Yifan , Mueller Frank
Published: January 2008

Contemporary processors support dynamic voltage scaling (DVS) to reduce power consumption by varying processor voltage/frequency dynamically. We develop power-aware feedback--DVS algorithms for hard real-time systems that adapt to dynamically changing workloads. The algorithms lower execution speed while guaranteeing timing constraints. We study energy consumption for synchronous and asynchronous DVS switching on a PowerPC board. Energy, measured via data acquisition, is reduced up to 70% over naïve DVS for our feedback scheme with 24% peak savings over previous algorithms. These results, albeit differing in quantity, confirm trends observed under simulation. They are the first of their kind on an embedded board.
Data cache locking for tight timing calculations
Authors: Vera Xavier , Lisper Björn , Xue Jingling
Published: January 2008

Caches have become increasingly important with the widening gap between main memory and processor speeds. Small and fast cache memories are designed to bridge this discrepancy. However, they are only effective when programs exhibit sufficient data locality. In addition, caches are a source of unpredictability, resulting in programs sometimes behaving in a different way than expected. Detailed information about the number of cache misses and their causes allows us to predict cache behavior and to detect bottlenecks. Small modifications in the source code may change memory patterns, thereby altering the cache behavior. Code transformations, which take the cache behavior into account, might result in a high cache performance improvement. However, cache memory behavior is very hard to predict, thus making the task of optimizing and timing cache behavior very difficult. This article proposes and evaluates a new compiler framework that times cache behavior for multitasking systems. Our method explores the use of
cache partitioning
and
dynamic cache locking
to provide worst-case performance estimates in a safe and tight way for multitasking systems. We use cache partitioning, which divides the cache among tasks to eliminate intertask cache interferences. We combine static cache analysis and cache-locking mechanisms to ensure that all intratask conflicts, and consequently, memory access times, are exactly predictable. The results of our experiments demonstrate the capability of our framework to describe cache behavior at compile time. We compare our timing approach with a system equipped with a nonpartitioned, but statically, locked data cache. Our method outperforms static cache locking for all analyzed task sets under various cache architectures, demonstrating that our fully predictable scheme does not compromise the performance of the transformed programs.
Meeting of the MINDS
Authors: Callan Jamie , Allan James , Clarke Charles L. A. , Dumais Susan , Evans David A. , Sanderson Mark , Zhai ChengXiang
Published: January 2008

Since its inception in the late 1950s, the field of Information Retrieval (IR) has developed tools that help people find, organize, and analyze information. The key early influences on the field are well-known. Among them are H. P. Luhn's pioneering work, the development of the vector space retrieval model by Salton and his students, Cleverdon's development of the Cranfield experimental methodology, Spärck Jones' development of
idf
, and a series of probabilistic retrieval models by Robertson and Croft. Until the development of the WorldWideWeb (Web), IR was of greatest interest to professional information analysts such as librarians, intelligence analysts, the legal community, and the pharmaceutical industry.
On the value of temporal information in information retrieval
Authors: Alonso Omar , Gertz Michael , Baeza-Yates Ricardo
Published: January 2008

Time is an important dimension of any information space and can be very useful in information retrieval. Current information retrieval systems and applications do not take advantage of all the time information available in the content of documents to provide better search results and user experience. In this paper we show some of the areas that can benefit from exploiting such temporal information.
The SIGIR 2007 workshop program
Authors: Mothe Josiane
Published: January 2008

The SIGIR workshop program aims at providing a framework for exploring new areas and ideas, and for presenting them in a less formal and possibly more focused way than the conference itself. It also encourages interaction with contributors and/or participants from related fields. These goals have been fully achieved in 2007
vintage
.
Workshop on web information seeking and interaction
Authors: Rodden Kerry , Ruthven Ian , White Ryen W.
Published: January 2008

The World Wide Web has provided access to a diverse range of information sources and systems. People engaging with this rich network of information may need to interact with different technologies, interfaces, and information providers in the course of a single search task. These systems may offer different interaction affordances and require users to adapt their information-seeking strategies. Not only is this challenging for users, but it also presents challenges for the designers of interactive systems, who need to make their own system useful and usable to broad user groups. The popularity of Web browsing and Web search engines has given rise to distinct forms of information-seeking behaviour, and new interaction styles, but we do not yet fully understand these or their implications for the development of new systems.
Plagiarism analysis, authorship identification, and near-duplicate detection PAN'07
Authors: Stein Benno , Koppel Moshe , Stamatatos Efstathios
Published: January 2008

Goal of the workshop was to bring together experts and prospective researchers around the exciting and future-oriented topic of plagiarism analysis, authorship identification, and high similarity search. This topic receives increasing attention, which results, among others, from the fact that information about nearly any subject can be found on the World Wide Web.
Improving non-English web searching (iNEWS07)
Authors: Lazarinis Fotis , Ferro Jesus Vilares , Tait John
Published: January 2008

This workshop attempted to promote the discussion and the research on non-English Web searching. Most search engines were first built for English. They do not take full account of inflectional semantics nor, for example, diacritics or the use of capitals. Our main aim was to discuss the additional problems faced in non-English Web queries and to suggest techniques to improve the response of searching systems. Papers related to Arabic, Basque, Farsi (Persian), Greek, Spanish, Swedish, Hindi, Bengali and other south asian languages were accepted. Conclusions were that search engines would be more effective if they took more account of the properties of individual languages, and that there is a need for more studies of real user behaviour in practical situations.
Multimedia information retrieval
Authors: van Zwol Roelof , Rüger Stefan , Sanderson Mark , Mass Yosi
Published: January 2008

With the rising popularity of rich media services such as Flickr, YouTube, and Jumpcut, new challenges in large scale multimedia information retrieval have emerged that not only rely on meta-data but on content-based information retrieval combined with the collective knowledge of users and geo-referenced meta-data that is captured during the creation process. For the future, it is envisioned that multimedia search in mobile environments or on P2P networks will take off on a large scale.
Information retrieval and applications of graphical models (IRGM 2007)
Authors: Fernández-Luna Juan M. , Piwowarski Benjamin , Huete Juan F.
Published: January 2008

Probabilistic models constitute an important kind of Information Retrieval (IR) model. They have been long and widely used [2], and offer a principled way of managing the uncertainty that naturally appears in many elements within this field. Nowadays, the dominant approach for managing probability within the field of Artificial Intelligence is based on the use of Bayesian Networks [15, 9], and these have also been used within IR as extensions of classical probabilistic models.
Report on the SIGIR 2007 workshop on focused retrieval
Authors: Trotman Andrew , Geva Shlomo , Kamps Jaap
Published: January 2008

On the 27th July 2007 the SIGIR 2007 Workshop on Focused Retrieval was held as part of SIGIR in Amsterdam, the Netherlands. Nine papers were presented in three sessions and in a fourth session there was a panel discussion. This report outlines the events of the workshop and summarizes the major outcomes.
Searching spontaneous conversational speech
Authors: de Jong Franciska , Oard Douglas W. , Ordelman Roeland , Raaijmakers Stephan
Published: January 2008

The SIGIR Workshop on Searching Spontaneous Conversational Speech was held as part of the 2007 ACM SIGIR Conference in Amsterdam. The workshop program was a mix of elements, including a keynote speech, paper presentations and panel discussions. This brief report describes the organization of this workshop and summarizes the discussions.
EVIA 2007
Authors: Sanderson Mark , Sakai Tetsuya , Kando Noriko
Published: January 2008

The first workshop on Evaluating Information Access was held at the National Institute of Informatics, Tokyo, Japan on May 15
th
, 2007. It was composed of a five invited speakers and two sessions of refereed papers and posters.
Query log analysis
Authors: Murray G. Craig , Teevan Jaime
Published: January 2008

Analysis of search engine query logs is an important tool for developers and researchers. However, the potentially personal content of query logs raises a number of questions about the use of that data. Privacy advocates are concerned about potential misuse of personal data; search engine providers are interested in protecting their users while maintaining a competitive edge; and academic researchers are frustrated by barriers to shared learning though shared data analysis. This paper reports on a workshop held at the WWW 2007 Conference to foster dialogue on the social and technical challenges that are posed by the content of query logs and the analysis of that content.
Feature generation for textual information retrieval using world knowledge
Authors: Gabrilovich Evgeniy
Published: January 2008

Imagine an automatic news filtering system that tracks company news. Given the news item "FDA approves ciprofloxacin for victims of anthrax inhalation", how can the system know that the drug mentioned is an antibiotic produced by Bayer? Or consider an information professional searching for data on RFID technology -- how can a computer understand that the item "Wal-Mart supply chain goes real time" is relevant for the search? Algorithms we present can do just that.