bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of intermediate principal stress on the deformation response of sand
Authors: Sãyao A , Vaid Y P 
Published: May 2008

An experimental investigation of the relevance of the intermediate principal stress (σ2) on the deformation response of a sand is presented. The effects of σ2 are conveniently studied through the nondimensional stress parameter b = (σ2  σ3)/(σ1  σ3). A series of stress path tests was performed on Ottawa sand specimens in a hollow cylinder torsional shear device. The experimental program includes shear loading at different values of b, and special b tests, in which b was continuously varied at different stress directions. It is shown that the b value may have a significant influence on the stressstrain response of sand, depending on the loading conditions. Key words: hollow cylinder tests, generalized stress paths, sand, stressstrain behaviour, intermediate principal stress.
Void redistribution in sand under post-earthquake loading
Authors: Boulanger Ross W , Truman Stephen P 
Published: May 2008

A mechanism for void redistribution in an infinite slope under post-earthquake loading conditions is described by consideration of the in situ loading paths that can occur under post-earthquake conditions and the results of triaxial tests designed to represent specific in situ post-earthquake loading paths. The mechanism is illustrated by application to an example problem. Void redistribution is shown to be a phenomena that may be more pronounced at the field scale than at the laboratory scale. Key words: liquefaction, earthquake, void redistribution, triaxial, sand.
The role of particle breakage in pile creep in sand
Authors: Leung C F , Lee F H , Yet N S 
Published: May 2008

It has been reported in the literature that the settlement of pile foundations in sand under sustained service loads is time dependent. As this phenomenon is not well understood, an experimental study is conducted to investigate the mechanism of pile creep in sand. In the first part of the study involving centrifuge modelling of piles, the test results show that the pile settlement increases with the logarithm of time and the rate of settlement increase is dependent upon the magnitude of applied load and sand density. The changes in the soil and pile stresses observed from instruments installed in the soil and along the pile shaft reveal that under sustained loads, stress relaxation takes place at and around the pile tip area with consequent stress transfer to the shaft. Associated ground surface settlement shows that creep is related to volumetric compression rather than dilation of sand. The centrifuge test findings are then related to the creep behaviour of sand subjected to one-dimensional compression. Examination of sand particles before and after sustained compression loads reveals that sand grains have been broken with their angular protrusions gradually ground off with time. The phenomena of sand particle breakage and stress relaxation around the pile tip provide evidence for the hypothesis that the observed creep is due to the progressive breakdown of sand particules. Key words: centrifuge models, creep, mechanism, one-dimensional compression, pile, sand.
Modelling of light nonaqueous phase liquid (LNAPL) releases into unsaturated sand
Authors: Knight M A , Mitchell R J 
Published: May 2008

Centrifuge physical modelling of light nonaquaeous phase liquid (LNAPL) transport in an unsaturated sand is discussed with regard to the similitude of the resulting three-fluid flow. Three model series are reported: the first to establish a reproducible unsaturated moisturesuction profile; the second to examine the modelling of models methodology for evaluating similitude of an LNAPL release into an unsaturated fine sand; and the third to prototype-scale data sets for 1000 L surface LNAPL releases at two different rates. Results show that a slower release rate produces deeper LNAPL penetration, and the reasons for this behaviour are discussed. An inexpensive and readily available numerical code called SWANFLOW was used to independently simulate the prototype release rates, and the results are compared with the centrifuge data. The numerical simulations produced compatible predictions of short-term oil transport but did not predict the observed longer term fate of the LNAPL in this highly nonlinear imbibitiondrainage problem. A numerical code that incorporates hysteresis between the imbibition and drainage curves would be expected to produce more complete long-term predictions. Key words: centrifuge modelling, numerical simulation, LNAPL fate, unsaturated sand.
Eighteenth Canadian Geotechnical Colloquium: Limit States Design For Foundations. Part I. An overview of the foundation design process
Authors: Becker Dennis E 
Published: May 2008

This paper examines the foundation design process in terms of level of safety associated with current state-of-practice, sources of uncertainty and how they are handled, importance of engineering judgement and experience, and the role of codes of practice. Working stress, limit states, reliability-based design approcahes are described and discussed in terms of their historical development, fundamental bases and differences, advantages, and limitations. Limit states are conditions under which a structure no longer performs its intended function. Limit states design considers seperately the two classes of ultimate and serviceability limit states using partial factors of safety. The European factored strength approach and the North American factored overall resistance approach are compared and discussed. The factored resistance approach is a logical extension of working stress design and has the significant advantage that it reflects not only uncertainty in strength, but also in theoretical models, site conditions, construction tolerances, and failure mechanisms. The partial load and resistance factors are interrelated and are a function of characteristic values. A consistent, rational basis for the selection of the geotechnical characteristic value is required. The use of a conservatively assessed mean value is recommended, and an approach for its interpretation is presented. Key words: limit states design, working stress design, characteristic value, partial factors, factored resistance, load and resistance factor design.
Modeling percent stocking changes for lodgepole pine stands in Alberta
Authors: Yang Yuqing , Huang Shongming 
Published: May 2008

A percent stocking change model was developed for lodgepole pine ( Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) in Alberta based on spatially mapped permanent sample plot data. Percent stocking was defined as the percentage of 10 m2 subplots occupied by at least one tree with a minimum height of 1.3 m. The difference equation technique was employed to fit the model. Three model forms were examined and the logistic function was chosen as the final model. Site index was found to be a significant predictor and incorporated into the model. Analyses revealed that the model had correlated, but homoskedastic errors and the correlated errors were modeled by spherical covariance structure using NLINMIX macro in SAS. A percent stocking index, defined as the percent stocking at 50 years total age, was introduced and derived from the developed model. The percent stocking model had both forward and backward projection capabilities. It was demonstrated, both on model fitting and validation data, that the model adequately portrayed the percent stocking dynamics of lodgepole pine stands in Alberta. The model also provided an important basis for creating linkages between reforestation survey results and future yield, which is crucial for sustainable forest management.
Mycorrhizal fungal community relationship to root nitrogen concentration over a regional atmospheric nitrogen deposition gradient in the northeastern USA
Authors: Lilleskov Erik A. , Wargo Philip M. , Vogt Kristiina A. , Vogt Daniel J. 
Published: May 2008

Increased nitrogen (N) input has been found to alter ectomycorrhizal fungal communities over short deposition gradients and in fertilization experiments; however, its effects over larger spatial scales have not been determined. To address this gap, we reanalyzed data from a study originally designed to examine the effects of soil aluminum/calcium (Al/Ca) ratios on the vitality of red spruce fine roots over a regional acid and N deposition gradient in the northeastern USA. We used root N as an indicator of stand N availability and examined its relationship with the abundance of ectomycorrhizal morphotypes. The dominant morphotypes changed in relative abundance as a function of stand N availability. As root N concentrations increased, Piloderma spp. - like, Cenococcum geophilum Fr., and other unidentified mycorrhizal morphotypes declined in abundance, while other smooth-mantled morphotypes increased. Root N concentration in the 1–2 mm diameter class was the best predictor of the abundance of multiple morphotypes. The morphotype responses were consistent with those found in experimental and small-scale studies, suggesting that N availability is altering ectomycorrhizal communities over broad spatial scales in this region. This finding provides an impetus to conduct a more detailed characterization of mycorrhizal community responses to N deposition across large-scale gradients.
Nitrogen limitation in a sweetgum plantation: implications for carbon allocation and storage
Authors: Iversen Colleen M. , Norby Richard J. 
Published: May 2008

The N status of temperate forests is closely linked to their C fluxes, and altered C or N availability may affect ecosystem C storage through changes in forest production and C allocation. We proposed that increased fine-root production previously observed in a sweetgum ( Liquidambar styraciflua L.) forest in response to elevated [CO2] was a physiological response to N limitation. To examine this premise, we fertilized plots in the sweetgum plantation adjacent to the Oak Ridge National Laboratory free-air CO2-enrichment (FACE) experiment. We hypothesized that N fertilization would increase sweetgum net primary production, leaf [N], and the relative flux of C to wood production. Annual additions of 200 kg·ha–1 of N as urea increased soil N availability, which increased stand net primary production, stand N uptake, and N requirement by about one-third. Increased leaf [N] and leaf area production in the fertilized plots increased stem production and shifted relative flux of C to wood production. We conclude that sweetgum production on this site is limited by soil N availability and a decreased fraction of net primary production in fine-root production with N addition is consistent with the premise that increased fine-root production in the adjacent FACE experiment is in response to N limitation.
Differences in fibre properties in cloned Norway spruce (Picea abies)
Authors: Zubizarreta Gerendiain A. , Peltola H. , Pulkkinen P. , Jaatinen R. , Pappinen A. 
Published: May 2008

In forest breeding programmes, growth has typically been used as a selection trait of prime importance in Norway spruce ( Picea abies (L.) Karst.), whereas less attention has been given to the wood and fibre characteristics. In the above context, we investigated phenotypic relationships between different fibre properties and growth and wood density traits in 20 cloned Norway spruce based on a clonal trial established in the 1970s in southeastern Finland. We found that fibre width showed, on average (2.9%), the lowest phenotypic variation followed by fibre wall thickness (3.4%), coarseness (5.5%), and fibre length (8.1%). All of the phenotypic correlations between the fibre properties were also positive (p < 0.05), ranging from moderate to strong, suggesting that selection for one trait could simultaneously affect the other traits. The phenotypic correlations, on average, were quite weak but positive between growth and fibre properties and slightly negative or weak positive between wood density and different fibre properties (p < 0.05). Individually, some of the clones showed negative correlation between growth traits and fibre length. As a result, selection for fibre properties alone could also reduce overall stem volume (or stem mass) and would not directly indicate wood density traits and vice versa.
Vegetation responses to stand structure and prescribed fire in an interior ponderosa pine ecosystemThis article is one of a selection of papers from the Special Forum on Ecological Studies in Interior Ponderosa Pine — First Findings from Blacks Mountain Interdisciplinary Research.
Authors: Zhang Jianwei , Ritchie Martin W. , Oliver William W. 
Published: May 2008

A large-scale interior ponderosa pine ( Pinus ponderosa Dougl. ex P. & C. Laws.) study was conducted at the Blacks Mountain Experimental Forest in northeastern California. The primary purpose of the study was to determine the influence of structural diversity on the dynamics of interior pine forests at the landscape scale. High structural diversity (HiD) and low structural diversity (LoD) treatments were created with mechanical thinning on 12 main plots. Each plot was then split in half with one-half treated with prescribed fire. During the 5 year period after the treatments, the LoD treatments showed slightly higher periodic annual increments for basal area (BA) and significantly higher diameter increments than did the HiD treatments, although HiD carried twice as much BA as LoD did immediately after the treatments. Prescribed fire did not affect growth, but killed and (or) weakened some trees. No interaction between treatments was found for any variable. Stand density was reduced from the stands before treatments, but species composition did not change. Old dominant trees still grew and large snags were stable during the 5 year period. Treatments had minor impacts on shrub cover and numbers. These results suggest that ponderosa pine forest can be silviculturally treated to improve stand growth and health without sacrificing understory shrub diversity.
Bird occupancy and richness in ponderosa pine forests with contrasting forest structure and fire historyThis article is one of a selection of papers from the Special Forum on Ecological Studies in Interior Ponderosa Pine — First Findings from Blacks Mountain Interdisciplinary Research.
Authors: George T. Luke , Zack Steve 
Published: May 2008

We compared the effects of two contrasting silvicultural treatments and prescribed fire on bird occupancy at Blacks Mountain Experimental Forest. Each silvicultural treatment was applied to two approximately 100 ha units within each of three blocks. Prescribed burning was applied to one-half of each silvicultural treatment in a split-plot design. Occupancy was estimated at eight points in each plot for 11 bird species and three foraging guilds (bark gleaners, woodpeckers, and foliage gleaners). The frequencies of species detections on the point counts were used to estimate species richness on each plot. Occupancy did not differ among treatments for any of the guilds. Four of the 11 bird species, the American robin ( Turdus migratorius L., 1766), the chipping sparrow ( Spizella passerina (Bechstein, 1798)), the white-breasted nuthatch ( Sitta carolinensis Latham, 1790), and the western tanager ( Piranga ludoviciana (A. Wilson, 1811)), showed responses to the treatments. Species richness did not differ between the silvicultural or the burn treatments. The general lack of response of the bird community to the silvicultural and burn treatments is likely a result of the relatively large size of the trees and snags retained on both silvicultural treatments, the low intensity of the prescribed burns, and the lack of a strong contrast in tree density between the silvicultural treatments.
REPUTATION FOR INNOVATING SOCIAL NETWORKS
Authors: CONTE ROSARIA , PAOLUCCI MARIO , SABATER-MIR JORDI 
Published: May 2008

Reputation is a fundamental instrument of partner selection. Developed within the domain of electronic auctions, reputation technology is being been imported by other applications, from social networks to institutional evaluation. Its impact on trust enforcement is uncontroversial and its management is of primary concern for entrepreneurs and other economic operators. In this paper, we will briefly report on simulation-based studies of the role of reputation as a more tolerant form of social capital than familiarity networks. Whereas the latter exclude nontrustworthy partners, reputation is a more inclusive mechanism on which larger and more dynamic networks are constructed. After the presentation of the theory of reputation developed by the authors in the last decade, a computational system (REPAGE) for forming and exchanging reputation information will be presented and findings from experimental simulations recently run on this system will be resumed. Final remarks and ideas for future work will conclude the paper.
Problems of the relationship between surface structure and deep displacements illustrated by the Zagros Range
Authors: Falcon N. L. 
Published: May 2008

Summary
The object of this paper is to discuss some of the unknown or little-known relationships between surface structure and deep displacements in the well-exposed Zagros orogenic belt of south-west Iran, which can be divided into three major structural belts. The subjective nature of all inferences about deep structure in the absence of seismic data supported by deep borehole evidence is accentuated. Only at relatively shallow depths where the rock succession is well known can concealed structure be predicted with confidence from surface geology alone.
Sedimentary thicknesses in orogenic belts
Authors: Stoneley R. 
Published: May 2008

Summary

The evidence provided by certain examples of thick sedimentary sequences, both deformed and undeformed, suggests that at least some of the geotectonic processes can be isolated whereby they are accommodated. These are (
a
) isostatic depression of oceanic crust by sedimentary loading, (
b
) down-dragging and compressional warping due to tangential crustal and sub-crustal displacements and (
c
) crustal foundering resulting from vertically acting changes in the mantle and/or lower crust. All three of these factors must be involved to some extent during the evolution of an orogenic belt but some features, such as the subsidence of a miogeosyncline under tension, are still difficult to explain. Within many Alpine orogenic zones, large thicknesses of sediment are found in miogeosynclines, eugeosynclines, flysch troughs and molasse basins but these four environments are not recognizable in all orogenic belts, particularly the older ones. Comparisons between different belts are not always meaningful in the framework of existing geosynclinal concepts and terminology, but it is expected that a new and comprehensive terminology, based on geotectonic considerations, may shortly become possible.
14. East Anglia and Essex
Authors: Evans Percy 
Published: May 2008

Summary
In this Section of the review discussion will be mainly concerned with fitting into the suggested time-scale those portions of the Eats Anglian succession that have an important bearing on the stratigraphy of other parts of England. It is convenient to begin with the younger beds.
The Hunstanton Till is assigned to the Weichselian because of the freshness of the associated land-forms; a variety of gravels (fluviatile and marine) can be placed in this stage through radiocarbon dating, direct correlation, or relation to the Ipswichian (Eemian). But the numerous problems of the East Anglian Weichselian seem to be mostly of a local nature.

The Ipswichian warm-climate deposits are securely correlated with the Eemian by their pollen diagrams. Their age is ioo to 7 ~ t.y., half-cycle 3 w. The Gipping glaciation is older, and since it is post-Hoxnian (Holsteinian) it must belong to some part of the Saale, either Drenthe or Warthe. The Drenthe glaciation (of 5 c) was the only terrestrial glaciation known to have invaded the Netherlands and the eastward prolongation of the general line of the Drenthe ice-front would bring it to Essex, whereas the Warthe ice-front was IOO to 2oo km farther north. Such a geographical correlation seems to have some merit in connexion with the later glaciations, but must have less force with earlier ice-sheets developed when topographical conditions were less like those of the present time. This
prima facie
evidence for the correlation of the Gipping is strongly upheld by the gradual uninterrupted passage
Occurrence, origin and significance of mechanically transported sulphide ores at Buchans, Newfoundland
Authors: Thurlow J. G. 
Published: May 2008

Summary

The Buchans orebodies are high-grade Kuroko-like massive sulphide deposits associated with Silurian (?) felsic volcanism of the northern Appalachians. Since 1928, 17 000 000 tons of ore has been mined, of which approximately one-half consists of mechanically transported sulphide breccia accumulations. Most of the transported ores occur as discrete orebodies composed of angular (competent) and wispy (plastic) sulphide fragments intimately mixed with a large variety of angular to rounded lithic fragments. Abundant evidence exists to suggest that these ores were fragmented by surface volcanic explosions and transported as rapidly moving sub-aqueous density flows. Fragmentation of the
in-situ
orebodies occurred intermittently throughout massive sulphide deposition and thus the zonation of the
in-situ
deposits is mimicked by zonation of the transported ores. These ores were preferentially deposited in palaeotopographic depressions along the path of density flow and maintain economic grade for distances in excess of 2 km from their source. Other deposits appear to have moved as slowly advancing ‘mud glaciers’.

The direction of transport can be determined from imbrication of ore fragments, direction of elongation of the ore zones and clast fabric, and from increasing ore grades, clast size and individual bed thickness in more proximal areas. Limited data on the distribution of disorganized, inverse to normally graded and normally graded beds yield transport directions compatible with those obtained from the other parameters. On the basis of the above criteria, as well as stratigraphic considerations and comparison of metal ratios in transported and
in-situ
deposits, the source of most transported ores can be identified as one of the two major
in-situ
massive sulphide deposits. At least one far-travelled sub-economic prospect has, however, no known source orebody.

In terms of exploration the Buchans orebodies are significant in that economic sulphide accumulations may occur as discrete transported orebodies well beyond the limits of stockwork mineralization and significant alteration.
Seismic constraints on the deep geology of the Caledonides of northern Britain
Authors: Bamford David 
Published: May 2008

Summary
Interpretation of compressional and shear wave data from the 1974 L.I.S.P.B. seismic experiment has resulted in a detailed crustal cross-section across the Caledonian orogenic belt of northern Britain. This section provides clear evidence of lateral variations in deep structure comparable with the gross geological variations: in particular crustal structure is asymmetric across the orogenic belt. The axis of this asymmetry seems to vary with depth within the central part of the belt but the evidence suggests that any Caledonian destructive plate boundary was located south of the Southern Uplands fault.