bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optimization of jet‐grouted support in NATM tunnelling
Authors: Pichler Christian , Lackner Roman , Martak Lothar , Mang Herbert A. 
Published: June 2004

AbstractAccording to its designation, horizontal jet grouting (HJG) is performed horizontally at the tunnel face in order to form a support structure of improved soil. HJG is employed to reduce the surface settlements in urban tunnelling when buildings and other infrastructure sensitive to settlements are encountered. The yet unanswered question arising from engineering practice of HJG refers to the optimal design of the jet‐grouted support structure and the underlying construction scheme. In this paper, numerical studies in the context of plane‐strain finite element (FE) analyses are presented, comparing different layouts of the support structure as well as different construction schemes. Moreover, the influence of the soil properties is investigated. On the basis of the numerical results, the optimal layout of the jet‐grouted support is identified for various soil stratifications including a homogeneous soil, a relatively soft layer of sand over a stiff layer of gravel, and the reverse situation. Sophisticated thermochemomechanical material models accounting for the strength and stiffness growth as well as chemical shrinkage and creep of cemented soil and shotcrete have been employed in the numerical investigations leading to the results reported in this work. Copyright © 2004 John Wiley & Sons, Ltd.
Regularized sequentially linear saw‐tooth softening model
Authors: Rots Jan G. , Invernizzi Stefano 
Published: June 2004

AbstractAfter a brief discussion on crack models, it is demonstrated that cracking is often accompanied by snaps and jumps in the load–displacement response which complicate the analysis. This paper provides a solution by simplifying non‐linear crack models into sequentially linear saw‐tooth models, either saw‐tooth tension‐softening for unreinforced material or saw‐tooth tension‐stiffening for reinforced material. A linear analysis is performed, the most critical element is traced, the stiffness and strength of that element are reduced according to the saw‐tooth curve, and the process is repeated. This approach circumvents the use of incremental–iterative procedures and negative stiffness moduli and is inherently stable. The main part of the paper is devoted to a regularization procedure that provides mesh‐size objectivity of the saw‐tooth model. The procedure is similar to the one commonly used in the smeared crack framework but, in addition, both the initial tensile strength and the ultimate strain are rescaled. In this way, the dissipated fracture energy is invariant with respect not only to the mesh size, but also to the number of saw‐teeth adopted to discretize the softening branch.Finally, the potential of the model for large‐scale fracture analysis is demonstrated. A masonry façade subjected to tunnelling induced settlements is analysed. The very sharp snap‐backs associated with brittle fracture of the façade automatically emerge with sequentially linear analysis, whereas non‐linear analysis of the façade using smeared or discrete crack models shows substantial difficulties despite the use of arc‐length schemes. Copyright © 2004 John Wiley & Sons, Ltd.
Chemo‐hygro‐mechanical modelling and numerical simulation of concrete deterioration caused by alkali‐silica reaction
Authors: Bangert F. , Kuhl D. , Meschke G. 
Published: June 2004

AbstractThe paper presents a macroscopic model for the description of concrete deterioration caused by alkali–silica reaction (ASR). Based on concepts of the Theory of Porous Media, concrete is regarded as a mixture of three superimposed and interacting constituents: the skeleton, the pore liquid and the pore gas. The skeleton in turn represents a mixture of the unreacted, unswollen and the already reacted, swollen material. When ASR takes place, mass of the unreacted material is non‐instantaneously converted into mass of the reacted material. Since the unreacted material is characterized by a smaller density, the material swells. In the proposed model the dependence of the kinetics and the magnitude of the swelling process on the moisture content is taken into account. The properties of the model are investigated by means of one‐dimensional parametric studies on the material level. Finally, the suitability of the model on the structural level is demonstrated by means of the numerical simulation of a concrete beam. It turns out, that deterioration by ASR is driven by the simultaneous activation of moisture diffusion and reaction kinetics resulting in a drastic reduction of the limit load and stiffness of concrete structures. Copyright © 2004 John Wiley & Sons, Ltd.
Subdivision schemes for smooth contact surfaces of arbitrary mesh topology in 3D
Authors: Stadler M. , Holzapfel G. A. 
Published: June 2004

AbstractThis paper presents a strategy to parameterize contact surfaces of arbitrary mesh topology in 3D with at least C1‐continuity for both quadrilateral and triangular meshes. In the regular mesh domain, four quadrilaterals or six triangles meet in one node, even C2‐continuity is attained. Therefore, we use subdivision surfaces, for which non‐physical pressure jumps are avoided for contact interactions. They are usually present when the contact kinematics is based on facet elements discretizing the interacting bodies. The properties of subdivision surfaces give rise to basically four different implementation strategies. Each strategy has specific features and requires more or less efforts for an implementation in a finite element program. One strategy is superior with respect to the others in the sense that it does not use nodal degrees of freedom of the finite element mesh at the contact surface. Instead, it directly uses the degrees of freedom of the smooth surface. Thereby, remarkably, it does not require an interpolation. We show how the proposed method can be used to parameterize adaptively refined meshes with hanging nodes. This is essential when dealing with finite element models whose geometry is generated by means of subdivision techniques. Three numerical 3D problems demonstrate the improved accuracy, robustness and performance of the proposed method over facet‐based contact surfaces. In particular, the third problem, adopted from biomechanics, shows the advantages when designing complex contact surfaces by means of subdivision techniques. Copyright © 2004 John Wiley & Sons, Ltd.
A contact algorithm for the Signorini problem using space–time finite elements
Authors: Pattillo P. D. , Tortorelli D. A. 
Published: June 2004

AbstractThe most common approach in the finite‐element modelling of continuum systems over space and time is to employ the finite‐element discretization over the spatial domain to reduce the problem to a system of ordinary differential equations in time. The desired time integration scheme can then be used to step across the so‐called time slabs, mesh configurations in which every element shares the same degree of time refinement. These techniques may become inefficient when the nature of the initial boundary value problem is such that a high degree of time refinement is required only in specific spatial regions of the mesh. Ideally one would be able to increase the time refinement only in those necessary regions. We achieve this flexibility by employing space–time elements with independent interpolation functions in both space and time. Our method is used to examine the classic contact problem of Signorini and allows us to increase the time refinement only in the spatial region adjacent to the contact interface. We also develop an interface‐tracking algorithm that tracks the contact boundary through the space–time mesh and compare our results with those of Hertz contact theory. Copyright 2004 John Wiley & Sons, Ltd.
On the Galerkin formulation of the smoothed particle hydrodynamics method
Authors: Cueto‐Felgueroso L. , Colominas I. , Mosqueira G. , Navarrina F. , Casteleiro M. 
Published: June 2004

AbstractIn this paper, we propose a Galerkin‐based smoothed particle hydrodynamics (SPH) formulation with moving least‐squares meshless approximation, applied to free surface flows. The Galerkin scheme provides a clear framework to analyse several procedures widely used in the classical SPH literature, suggesting that some of them should be reformulated in order to develop consistent algorithms. The performance of the methodology proposed is tested through various dynamic simulations, demonstrating the attractive ability of particle methods to handle severe distortions and complex phenomena. Copyright © 2004 John Wiley & Sons, Ltd.
Optimization by random search with jumps
Authors: Li Chunshien , Priemer Roland , Cheng Kuo‐Hsiang 
Published: June 2004

AbstractWe give a random optimization (RO) algorithm to optimize a real‐valued function of n real variables. During the optimization process, interpolation points are examined to follow valleys, and jumps to new starting points are executed to avoid numerous iterations in local minima. Convergence with probability one to the global minimum of a function is proved. The proposed RO method is a simple, derivative‐free and computationally moderate algorithm, with excellent performance compared to other RO methods. Seven functions, which are commonly used to test the performance of optimization methods, are used to evaluate the performance of the RO algorithm given here. Copyright © 2004 John Wiley & Sons, Ltd.
A new extension of the natural element method for non‐convex and discontinuous problems: the constrained natural element method (C‐NEM)
Authors: Yvonnet J. , Ryckelynck D. , Lorong P. , Chinesta F. 
Published: June 2004

AbstractIn this paper a new extension of the mesh‐free natural element method (NEM) is presented. In this approach, coined as constrained natural element method (C‐NEM), a visibility criterion is introduced to select natural neighbours in the computation of the shape functions. The computation of these shape functions is based on a modified, constrained Voronoi diagram. With this technique, some difficulties inherent to this method in non‐convex domains are avoided and the analysis of problems involving cracks or discontinuities are now easily performed. As the NEM satisfies the Kronecker delta property, the imposition of essential boundary conditions is trivial, unlike other mesh‐free methods. The C‐NEM technique provides a description of integration cells that allows the use of the stabilized conforming nodal integration (SCNI) scheme instead of Gauss integration to enhance computational efficiency and accuracy. Two numerical examples in elastostatics are reported to evaluate the potential of the proposed technique in highly non‐convex geometries, like a crack, through which the solution becomes discontinuous. Copyright © 2004 John Wiley & Sons, Ltd.
Carbon and nitrogen stable isotopes as tracers of change in diet breadth during Middle and Upper Palaeolithic in Europe
Authors: Drucker D. , Bocherens H. 
Published: June 2004

AbstractCarbon and nitrogen stable isotope ratios in fossil bone collagen have been used as evidence for an increase of diet breadth between Middle Palaeolithic Neanderthals and Early Upper Palaeolithic anatomically modern humans. In this paper, we revisit the rules of palaeodietary reconstruction using collagen stable isotopes and reassess the possible isotopic signatures of potential protein resources available to prehistoric humans. It appears that the interpretation of the human's isotopic signature does not necessarily imply a significant proportion of aquatic‐derived protein in the diet neither for Neandertal nor for first anatomically modern humans in Europe. Exploitation of aquatic ecosystems by humans needs to be supported by further zooarchaeological evidence. Nevertheless, isotopic biogeochemistry of fossil human collagen can be very useful in palaeodietary reconstructions provided that basic rules are followed while selecting samples of coeval fauna, in order to establish the end members of different food resources. Significant progress investigating the evolution of subsistence strategies in fossil hominids is expected from a combination of zooarchaeological and isotopic data. Copyright © 2004 John Wiley & Sons, Ltd.
Neanderthal–modern human competition? A comparison between the mammals associated with Middle and Upper Palaeolithic industries in Europe during OIS 3
Authors: Stewart J. R. 
Published: June 2004

AbstractThe extinction of the Neanderthals is generally believed to be due to interspecific competition with modern humans. This hypothesis is tested using the faunas accompanying Upper and Middle Palaeolithic archaeology in Europe dating to OIS 3 and the start of OIS 2 (60–20 ka BP). The issue is also considered in the light of ecological theory, controlled experiments and field studies of competition between congeneric species. This paper concludes that competition between modern humans and Neanderthals is not easily demonstrated and that if it did exist it need not have caused Neanderthal extinction. Copyright © 2004 John Wiley & Sons, Ltd.
Vanishing carnivores: what can the disappearance of large carnivores tell us about the Neanderthal world?
Authors: Estévez Jordí 
Published: June 2004

AbstractThis paper examines the relationship between the extinction of carnivores and the disappearance of the Neanderthals. The Iberian Peninsula, as the westernmost point of Eurasia, is the key for an understanding of either the replacement or the continuity of hominids. Cave bear evolutionary history shares some trends with that of the Neanderthals. This means that most of the causes cited to explain the disappearance of Neanderthals have some implications that are linked with this carnivore's history. Some of the causes for the extinction of both are presented together and discussed. We analyse the contrast between the evidence from both central Europe and the Iberian Peninsula, which suggests a cause different from mere climatic stress for the extinction. The problems of the Iberian archaeological record are revised and we stress the need for a large European research programme to verify the data. Copyright © 2004 John Wiley & Sons, Ltd.
Middle Palaeolithic subsistence in the Lone Valley (Swabian Alb, southern Germany)
Authors: Krönneck P. , Niven L. , Uerpmann H.‐P. 
Published: June 2004

AbstractSouthern Germany is rich with Palaeolithic cave sites, many of which are concentrated in the extensive karst systems of several river valleys. Artefact inventories and faunal assemblages from these sites are renowned but less is known about the Middle Palaeolithic faunas. This paper provides an evaluation of faunas from key Middle Palaeolithic cave localities of the Lone Valley including new results from the sites of Bockstein and Vogelherd. These assemblages reflect high species diversity, particularly of large‐ and medium‐sized herbivores as well as large carnivores. Horse is the most frequent prey animal in both Bocksteinschmiede III and Vogelherd VII. Several anthropogenic signatures characterize the Bocksteinschmiede III fauna, but the role of hominids is less clear in the bone accumulation from Vogelherd VII. Copyright © 2004 John Wiley & Sons, Ltd.
Change and continuity in subsistence during the Middle and Upper Palaeolithic in the Ach Valley of Swabia (south‐west Germany)
Authors: Münzel S. C. , Conard N. J. 
Published: June 2004

AbstractThis paper examines the faunal assemblages from Middle Palaeolithic cave sites in the Ach Valley and views them in a broader chronological context along with the Upper Palaeolithic assemblages of the region. We present data from the key Middle Palaeolithic sites of Geißenklösterle, Sirgenstein, Große Grotte and Kogelstein. Except Kogelstein, which is a hyena den, the other three sites served as cave bear hibernation dens, where cave bear is the most abundant species. The most frequent game species during the Upper Palaeolithic are horse, mammoth and reindeer. But these animals are mainly represented by specific skeletal elements, which were important as raw material for the production of organic tools. The large variety of organic tools made from bone, antler, and ivory, and the refuse resulting from their production in Upper Palaeolithic layers stands in contrast to the extreme rarity of organic tools and production debris in Middle Palaeolithic layers. The faunal assemblages in the Ach Valley document continuity in the seasonal use of the landscape and the preferred game, but reflect changes in the use of sites and organic technology between the Middle and the Upper Palaeolithic. Based on the faunal and lithic assemblages from the caves of the Ach Valley, most of the sites were used more intensively in the Upper Palaeolithic than in the Middle Palaeolithic. If these assemblages provide representative samples, the available data suggest lower population densities and greater mobility of Neanderthals during the Middle Palaeolithic than of modern humans during the Upper Palaeolithic. Copyright © 2004 John Wiley & Sons, Ltd.
Faunal analysis from Amud Cave: preliminary results and interpretations
Authors: Rabinovich Rivka , Hovers Erella 
Published: June 2004

AbstractThe Late Mousterian Neanderthal site of Amud Cave (dated ca. 70–55 kyr) is situated on the margins of the Dead Sea Rift, about 5 km northwest of the Sea of Galilee. Recent excavations at the site yielded rich lithic, faunal and human skeletal assemblages. This paper presents some characteristics of the faunal assemblages from Amud Cave, combined with pertinent results of taphonomic and micromorphological studies, and places them in the context of other Late Mousterian archaeofaunas in the southern Levant. Copyright © 2004 John Wiley & Sons, Ltd.
Variation in mortality profiles of red deer (Cervus elaphus) in Middle Palaeolithic assemblages from western Europe
Authors: Steele T. E. 
Published: June 2004

AbstractPrey age‐at‐death is often used to assess hunting strategies, but the age profiles of animals represented in Middle Palaeolithic ungulate assemblages vary through time and across space. Understanding this diversity is important for reconstructing human behavioural evolution. To explore this issue, I studied one species, red deer (Cervus elaphus), in late Acheulean and Middle Palaeolithic assemblages from France (Combe‐Grenal, Lazaret, and Piégu) and northern Spain (Gabasa 1 and Labeko Koba). I reconstructed age distributions using three methods: histograms, boxplots of median crown heights, and modified triangular plots, and two tooth combinations: dp4/p4 and dp4/m1. Two modern samples served as comparative baselines: a sample of C. elaphus killed by modern hunters in western Montana, USA and a sample of C. elaphus hunted by wolves reintroduced into Yellowstone National Park, Wyoming, USA. The mortality distributions of the modern samples differ dramatically. The wolf‐hunted sample contains more juvenile and old individuals, while the human‐hunted sample has more young adults. The fossil age structures fall into two clusters: 1) Gabasa 1 and Labeko Koba with a high proportion of juvenile red deer and few prime‐aged adults, and 2) Combe‐Grenal, Lazaret, and Piégu with equal abundances of juvenile and prime‐aged red deer. I consider possible explanations for this pattern. More sites and more detailed analyses are needed to determine conclusively that the difference is related ancient human behaviour and not other pre‐ and post‐depositional processes. However, the assemblage from Gabasa Cave is important for demonstrating that deciduous teeth can be well preserved in the Late Pleistocene fossil record. Copyright © 2004 John Wiley & Sons, Ltd.
Expectations, performance, and citizen satisfaction with urban services
Authors: Van Ryzin Gregg G. 
Published: June 2004

AbstractThe expectancy disconfirmation model has dominated private‐sector research on customer satisfaction for several decades, yet it has not been applied to citizen satisfaction with urban services. The model views satisfaction judgments as determined—not just by product or service performance—but by a process in which consumers compare performance with their prior expectations. Using data from a New York City citizen survey, this study finds that citizen expectations, and especially the disconfirmation of expectations—factors that previously have not been considered in empirical studies of the determinants of citizen satisfaction—play a fundamental role in the formation of satisfaction judgments regarding the quality of urban services. Interestingly, the modeling results suggest that urban managers should seek to promote not only high‐quality services, but also high expectations among citizens. Additional implications for research and public management practice are discussed. © 2004 by the Association for Public Policy Analysis and Management.
Does merit pay reward good teachers? Evidence from a randomized experiment
Authors: Dee Thomas S. , Keys Benjamin J. 
Published: June 2004

AbstractA common criticism of merit‐pay plans is that they fail to systematically target rewards to the most effective teachers. This study presents new evidence on this issue by evaluating data from Tennessee's Career Ladder Evaluation System and the Project STAR class‐size experiment. Because the students and teachers participating in the experiment were randomly assigned, inferences about the relative quality of teachers certified by the career ladder should be unbiased. The results indicate that Tennessee's career ladder had mixed success in rewarding teachers who increased student achievement. Assignment to career‐ladder teachers increased mathematics scores by roughly 3 percentile points but generally had smaller and statistically insignificant effects on reading scores. © 2004 by the Association for Public Policy Analysis and Management.
Stigma and other determinants of participation in TANF and Medicaid
Authors: Stuber Jennifer , Kronebusch Karl 
Published: June 2004

AbstractWe developed a conceptual framework to examine the association between stigma, enrollment barriers (e.g., difficult application), knowledge, state policy, and participation in the Temporary Assistance to Needy Families (TANF) and adult Medicaid programs. Survey data from 901 community health center patients, who were potential and actual participants in these programs, indicated that while images of the Medicaid program and its recipients were generally positive, stigma associated with welfare stereotypes reduced both TANF and Medicaid enrollment. Expectations of poor treatment when applying for Medicaid, enrollment barriers, and misinformation about program rules were also associated with reduced Medicaid enrollment. States that enacted strict welfare reform policies were potentially decreasing TANF participation, while states with more simplified and generous programs were potentially increasing Medicaid participation. The results suggest that the image of the adult Medicaid program remains tied to perceptions about welfare and provides guidance to policymakers about how to improve participation rates. © 2004 by the Association for Public Policy Analysis and Management.
Collaborative environmental institutions: All talk and no action?
Authors: Lubell Mark 
Published: June 2004

AbstractMany analysts view collaborative institutions that attempt to forge consensus and build cooperation among conflicting stakeholders as a potential remedy to the pathologies of conventional environmental policy. However, few analyses have demonstrated that collaborative institutions actually increase levels of cooperation, and critics accuse collaborative institutions of all talk and no action. This paper reports the use a quasi‐experimental design to compare the levels of consensus and cooperation in coastal watersheds with and without U.S. EPA's National Estuary Programs, one of the most prominent national examples of collaborative institutions in the environmental policy domain. Panel survey data from more than 800 respondents shows that while the level of consensus is higher in NEP estuaries, there is no difference between NEP and non‐NEP estuaries in the level of cooperation. © 2004 by the Association for Public Policy Analysis and Management.