bluuebunny/crossref_metadata_2025 huggingface dataset:
Mid-Holocene presence of water chestnut (Trapa natans L.) in the meres of Holderness, East Yorkshire, UK
Authors: Schofield J. E. , Bunting M. J.
Published: June 2005

Palaeoenvironmental and radiocarbon data are presented from an infilled freshwater basin (Lambwath Mere) in Holderness, East Yorkshire (UK). The site contains a rare and detailed c. 4000 cal. yr mid-Holocene pollen record for the floating-leaved aquatic plant Trapa natans (L.) (water chestnut). Competing hypotheses (natural and anthropogenic) to explain the earlier presence of this ‘exotic’ species in Holderness are evaluated. Maximum Trapa frequencies date to the interval 6200-4200 cal. BP and are shown to occur during shallow open water conditions just prior to overgrowth of the basin by semiterrestrial vegetation communities. There is no clear palynological or archaeological evidence from the site to suggest settlement or significant human activity around the mere during this episode. It appears more likely that the occurrence of water chestnut at this site can be explained through natural factors (a combination of a favourable climate and the availability of a suitable habitat) rather than as a prehistoric human introduction.
A sediment-based multiproxy palaeoecological approach to the environmental archaeology of lake dwellings (crannogs), central Ireland
Authors: O'Brien Charlotte , Selby Katherine , Ruiz Zoe , Brown Anthony , Dinnin Mark , Caseldine Chris , Langdon Pete , Stuijts Ingelise
Published: June 2005

A multiproxy study of Ballywillin Crannog, Lough Kinale, central Ireland is presented. The methodology used reveals the wealth of information that a multiproxy approach can contribute in lake settlement studies. Plant macrofossils, pollen and spores, diatoms, chironomids and Coleoptera from a lake core are used to reconstruct local and regional vegetation change and lake history to establish the age and function of the crannog. The palaeoecological evidence suggests that Ballywillin Crannog was constructed around AD 620, with its most intensive period of occupation after AD 11 50. Cereals and a range of gathered fruits and nuts were brought onto and cooked on the crannog, and cereal grains were possibly stored there.
Palaeoecology of Lake Zeribar, Iran, in the Pleniglacial, Lateglacial and Holocene, reconstructed from plant macrofossils
Authors: Wasylikowa Krystyna
Published: June 2005

Changes in aquatic and marsh vegetation at Lake Zeribar in the Zagros Mountains, Iran, during the last 40 000 years were reconstructed on the basis of plant macrofossils. Several episodes of low water level and increased salinity were evidenced by peaks of Chenopodium rubrum seeds and the occurrence of obligate (Salicornia sp., Ruppia maritima and Suaeda sp.) and facultative (Zannichellia palustris) halophytic macrophytes as well as brackish water and marine diatoms. Some of these events can be correlated with an increase in diatoms indicative of higher conductivity and with changes in oxygen-isotope data. They are interpreted as the expression of general climatic dryness, although water-level changes might also have resulted from episodes of deposition on the alluvial fans that dam the lake. A few such water-level changes occurred in the Pleniglacial. The most pronounced lowering corresponds to the Younger Dryas interval of high climatic aridity. Macrofossil indicators of water-level changes appeared also in the Holocene section of the profiles at the same time as Quercus expanded on the surrounding uplands, culminating about 6000- 5000 14C yr BP, giving support to the hypothesis that the delay of forest expansion in this part of the Zagros Mountains was caused by climatic dryness.
Alluvial stratigraphic evidence for channel incision during the Mediaeval Warm Period on the central Great Plains, USA
Authors: Daniels J. Michael , Knox James C.
Published: June 2005

Alluvial valley fills from tributaries to the upper Republican River, southwest Nebraska, USA, provide soil- and morpho-stratigraphic evidence for an episode of channel incision that occurred between c. 1100 and 800 14C yr BP, based on 11 new radiocarbon ages. This local episode of channel incision correlates with other alluvial stratigraphic studies from the central Great Plains and demonstrates regionally synchronous fluvial behaviour. Proxy records of palaeohydrologic conditions in and around the Great Plains (including lacustrine, aeolian and geomorphological sources) indicate that channel incision correlates with a multicentennial episode of common, widespread drought. Temporally, this drought episode corresponds to the period recognized in many regions as the Mediaeval Warm Period (MWP). Therefore, this research demonstrates: (1) a relationship in the semi-arid central Great Plains between drought and increased fluvial incision; and (2) a local/regional geomorphic response to a particular episode of global climate change.
‘Little Ice Age’ proxy glacier mass balance records reconstructed from tree rings in the Mt Waddington area, British Columbia Coast Mountains, Canada
Authors: Larocque Sonya J. , Smith Dan J.
Published: June 2005

The intention of this research was to explore whether dendroclimatological relationships could be used to reconstruct long-term proxy records of ‘Little Ice Age’ glacier mass balance changes in the southern Coast Mountains of British Columbia. Tree-ring width chronologies from the Mt Waddington area were used in concert with historical glacier records to construct models spanning the past 450 years. The approach was to build models that were based on derived relationships between tree-ring growth and glacier mass balance: (1) warmer temperatures in the summer positively influence tree growth but are detrimental to glacier health; (2) colder temperatures during the winter and deeper snowpack have a negative impact on tree growth, whereas they are related to greater accumulation on the glacier during the winter season. Stepwise regression analyses were applied to tree-ring chronologies to predict glacier mass balance at local and regional scales. The models of net annual balance for the region (regional data set) show that periods of positive mass balance occurred in the AD 1750s, 1820s to 1830s and 1970s. Peaks of winter balance correspond closely to these periods, showing a sharp drop in winter mass balance towards the end of the nineteenth century. Wavelet analyses suggest that glacial mass balance regimes in the region respond synchronously to Pacific Ocean circulation systems such as the El Niño Southern Oscillation and the Pacific Decadal Oscillation.
Effects of sample mass and macrofossil type on radiocarbon dating of arctic and boreal lake sediments
Authors: Oswald W. Wyatt , Anderson Patricia M. , Brown Thomas A. , Brubaker Linda B. , Hu Feng Sheng , Lozhkin Anatoly V. , Tinner Willy , Kaltenrieder Petra
Published: June 2005

Dating lake sediments by accelerator mass spectrometry (AMS) 14C analysis of terrestrial plant macrofossils overcomes one of the main problems associated with dating bulk sediment samples, i.e., the presence of old organic matter. Even so, many AMS dates from arctic and boreal sites appear to misrepresent the age of the sediment. To understand the nature of these apparent dating anomalies better, we conducted a series of 14C dating experiments using samples from Alaskan and Siberian lake-sediment cores. First, to test whether our analytical procedures introduced a sample-mass bias, we obtained 14C dates for different-sized pieces of single woody macrofossils. In these sample-mass experiments, statistically equivalent ages were found for samples as small as 0.05 mg C. Secondly, to assess whether macrofossil type influenced dating results, we conducted sample-type experiments in which 14C dates were obtained for different macrofossil types sieved from the same depth in the sediment. We dated materials from multiple levels in sediment cores from Upper Capsule Lake (North Slope, northern Alaska) and Grizzly Lake (Copper River Basin, southern Alaska) and from single depths in other records from northern Alaska. In several of the experiments there were significant discrepancies between dates for different plant tissues, and in most cases wood and charcoal were older than other macrofossil types, usually by several hundred years. This pattern suggests that 14C dates for woody macrofossils may misrepresent the age of the sediment by centuries, perhaps because of their longer terrestrial residence time and the potential in-built age of longlived plants. This study identifies why some 14C dates appear to be inconsistent with the overall age-depth trend of a lake-sediment record, and it may guide the selection of 14C samples in future studies.
Late-Holocene alluvial events in the Central Apennines, Italy
Authors: Giraudi C.
Published: June 2005

A stratigraphic sequence was identified in the Gran Sasso Massif (Central Apennines, Italy), consisting of alluvial sediments and buried soils. The soils, dated by the radiocarbon method, enabled various alluvial phases that have occurred in the last 2500 years to be chronologically framed. These phases were then correlated with the frequency of the Tiber floods at Rome and with the progradation of its delta. The phases of soil burial by alluvial sediments coincide with the periods of intense flooding of the Tiber at Rome (between the second century Bc and the second century AD, between the sixth and the ninth centuries AD, and between the fifteenth and the nineteenth centuries AD) and with periods of strong progradation of the river delta. On the basis of the chronological correlation between alluvial phases, glacial variations, and oscillations in the levels of Lakes Fucino and Trasimeno, it was then possible to establish that, corresponding to the alluvial phases, the hydrological balance of the lakes was positive and, in two of the three cases, the increased flood frequency coincided with the phases of advance of the only glacier located in the Apennines.
Henry Kandrup's Ideas About Relaxation of Stellar Systems
Authors: MERRITT DAVID
Published: June 2005

Abstract: Henry Kandrup wrote prolifically on the problem of relaxation of stellar systems. His picture of relaxation was significantly more refined than the standard description in terms of phase mixing and violent relaxation. In this article, I summarize Henry's work in this and related areas.
Chaotic Collisionless Evolution in Galaxies and Charged‐Particle Beams
Authors: KANDRUP HENRY E. , BOHN COURTLANDT L. , KISHEK RAMI A. , O'SHEA PATRICK G. , REISER MARTIN , SIDERIS IOANNIS V.
Published: June 2005

Abstract:Both galaxies and charged particle beams can exhibit collisionless evolution on surprisingly short time scales. This can be attributed to the dynamics of chaotic orbits. The chaos is often triggered by resonance caused by time dependence in the bulk potential, which acts almost identically for attractive gravitational forces and repulsive electrostatic forces. The similarity suggests that many physical processes at work in galaxies, although inaccessible to direct controlled experiments, can be tested indirectly via controlled experiments with charged particle beams, such as those envisioned for the University of Maryland electron ring currently nearing completion.
Chaotic Dynamics in Charged‐Particle Beams: Possible Analogs of Galactic Evolution
Authors: BOHN COURTLANDT L.
Published: June 2005

Abstract: During the last couple of years of his life, Henry Kandrup became intensely interested in using charge‐particle beams as a tool for exploring the dynamics of evolving galaxies. He and I recognized that both galaxies and charged‐particle beams can exhibit collisionless relaxation on surprisingly short time scales, and that this circumstance can be attributed to phase mixing of chaotic orbits. The chaos is often triggered by resonances caused by time dependence in the bulk potential, which acts almost identically for attractive gravitational forces as for repulsive electrostatic forces superposed on external focusing forces. Together we published several papers concerning evolving beams and galaxies, papers that relate to diverse topics such as the physics of chaotic mixing, the applicability of the Vlasov‐Poisson formalism, and the production of diffuse halos. We also teamed with people from the University of Maryland to begin designing controlled experiments to be done at the University of Maryland electron ring. This paper highlights our collaborative findings as well as plans for future investigations that the findings have motivated.
The University of Maryland Electron Ring: A Platform For Study of Galactic Dynamics on a Laboratory Scale
Authors: KISHEK R A. , O'SHEA P.G. , BERNAL S , HABER I , HARRIS J R. , HUO Y , LI H , REISER M
Published: June 2005

Abstract:The University of Maryland electron ring (UMER) is a novel experimental storage ring designed to investigate the dynamics of large systems of collisionless particles that nevertheless interact via collective mechanisms. Heavily diagnosed and designed to circulate a 100 mA electron beam at 10 keV for several turns, UMER allows us to follow the evolution of the beam over a large number of dynamical periods. Given the similarity of dynamics between the Coulomb forces and gravitational forces, it is possible to design beam experiments that will simulate such astrophysical events as galactic merger, for instance. The cros‐comparison of beam experiments with accelerator simulation codes provides invaluable benchmarks of transient processes akin to, for example, violent relaxation in stellar systems that are otherwise impossible to obtain.
Wavelet‐Based Poisson Solver for Use in Particle‐in‐Cell Simulations
Authors: TERZIĆ BALSA , POGORELOV ILYA V.
Published: June 2005

Abstract: We report on a successful implementation of a wavelet‐based Poisson solver for use in three‐dimensional particle‐in‐cell simulations. Our method harnesses advantages afforded by the wavelet formulation, such as sparsity of operators and data sets, existence of effective preconditioners, and the ability simultaneously to remove numerical noise and additional compression of relevant data sets. We present and discuss preliminary results relating to the application of the new solver to test problems in accelerator physics and astrophysics.
Energy Trapping in Loaded String Models with Long‐ and Short‐Range Couplings
Authors: POGORELOV ILYA V. , KANDRUP HENRY E.
Published: June 2005

Abstract: This paper illustrates the possibility, in simple loaded string models, of trapping most of the system energy in a single degree of freedom for very long times, demonstrating in particular that the robustness of the trapping is enhanced by increasing the connectance of the system, that is, the extent to which many degrees of freedom are coupled directly by the interaction Hamiltonian and/or the strength of the couplings.
Characterization of Chaos: A New, Fast, and Effective Measure
Authors: SIDERIS IOANNIS V.
Published: June 2005

Abstract: A new technique for characterization of the regular or chaotic nature of dynamical orbits has been discovered. It takes advantage of morphological and dynamical properties of orbits, and is very effective, at least for tim‐independent systems with two degrees of freedom. The new technique was initially designed with time‐dependent and N‐body systems in mind. For this reason one of its main goals is to provide straightforward information about the transient chaos associated with such regimes. Equally important is the distinction it can provide between sticky and wildly chaotic epochs during the evolution of chaotic orbits. The most important advantage over the existing methods is that it can characterize an orbit using a very small number of orbital periods. For these reasons the new method is extremely promising to be useful and effective in a broad spectrum of disciplines.
Hard Sphere Dynamics for Normal and Granular Fluids
Authors: DUFTY JAMES W. , BASKARAN APARNA
Published: June 2005

Abstract: A fluid of N smooth, hard spheres is considered as a model for normal (elastic collision) and granular (inelastic collision) fluids. The potential energy is discontinuous for hard spheres so that the pairwise forces are singular and the usual forms of Newtonian and Hamiltonian mechanics do not apply. Nevertheless, particle trajectories in the N particle phase space are well defined and the generators for these trajectories can be identified. The first part of this presentation is a review of the generators for the dynamics of observables and probability densities. The new results presented in the second part refer to applications of these generators to the Liouville dynamics for granular fluids. A set of eigenvalues and eigenfunctions of the generator for this Liouville dynamics system is identified in a special stationary representation. This provides a class of exact solutions to the Liouville equation that are closely related to hydrodynamics for granular fluids.
Nonlinear Stability of Newtonian Galaxies and Stars from a Mathematical Perspective
Authors: REIN GERHARD
Published: June 2005

Abstract: The stability of equilibrium configurations of galaxies or stars are time honored problems in astrophysics. We present mathematical results on these problems that have recently been obtained by Yan Guo and the author in the context of the Vlasov‐Poisson and the Euler‐Poisson models. Based on a careful analysis of the minimization properties of conserved quantities—the total energy and so called Casimir functionals—nonlinear stability results are obtained for a wide class of equilibria.
Chaos in Orbits Due to Disk Crossings
Authors: HUNTER C.
Published: June 2005

Abstract: We study orbits of halo stars in simple models of galaxies with disks and halos to see if the cumulative effects of the sudden changes in acceleration that occur at disk crossings can induce chaos. We find that they can, although not in all orbits and not in all potentials. Most of the orbits that become chaotic stay relatively close to the disk and range widely in the radial direction. Heavier disks and increased halo flattening both enhance the extent of the chaos. A limited range of experiments with a three‐component model of the Milky Way with an added central bulge finds that many chaotic disk‐crossing orbits can be expected in the central regions, and that prolateness of the halo is much more effective than oblateness in generating chaos.
Systems with Escapes
Authors: CONTOPOULOS G , HARSOULA M
Published: June 2005

Abstract: There are two types of escapes in conservative dynamical systems with two degrees of freedom: escapes to infinity and escapes to certain singular points at a finite distance. In both cases the areas on a surface of section are not preserved. We consider the basins of escape to infinity in simple Hamiltonian systems. The initial conditions of orbits escaping after 1, 2, … intersections with a surface of section form in general spiral fractal sets. Then we consider the sets of escapes into two fixed black holes for various values of the energy. The forms of these sets depend on the unstable periodic orbits and their asymptotic curves. We find the characteristics of the simple periodic orbits and their changes for various values of the energy.
On Bars and Haloes: Their Interaction and Their Orbital Structure
Authors: ATHANASSOULA E.
Published: June 2005

Abstract: A live halo plays an active role in the formation and evolution of bars by participating in the angular momentum redistribution that drives the dynamical evolution. Angular momentum is emitted mainly by neae‐resonant material in the bar region and is absorbed mainly by near‐resonant material in the halo and in the outer disc. This exchange determines the strength of the bar, the decrease in its pattern speed, as well as its morphology. Thus, contrary to previous beliefs, a halo can help the bar grow, so that bars growing in galaxies with responsive massive haloes can become stronger than bars growing in disc dominated galaxies. During the evolution the halo does not stay axisymmetric. It forms a bar that is shorter and fatter than the disc bar and stays so throughout the simulation, although its length grows considerably with time. I discuss the orbital structure in the disc and the halo and compare it with periodic orbits in analytical barred galaxy potentials. A central mass concentration (e.g., a central black hole or a central disc) weakens a bar and increases its pattern speed. The effect of the central mass concentration depends strongly on the model, being less strong in models with a massive concentrated halo and a strong bar.
The Basic Dynamical Mechanism in Spiral Galaxies
Authors: PFENNIGER DANIEL , REVAZ YVES
Published: June 2005

Abstract: This paper explicates the most fundamental mechanism that rules spiral galaxies. Although spiral galaxies are complex systems for which we do not yet have a complete understanding, the dark matter being the most severe unknown, it is possible to pinpoint the few physical factors that determine their most important properties, such as bars and spiral arms. Dynamics linked to the dissipative nature of gas and its transformation into stars provides clues that spiral galaxies are driven by dissipation close to a state of marginal stability with respect to the dynamics in the galaxy plane. Here, we present numerical evidence suggesting that warps play a similar role but in the transverse direction. N‐body simulations show that typical galactic disks are also marginally stable with respect to a bending instability, leading to typical observed warps. The frequent occurrence of warps and asymmetries in the outer galactic disks, like bars in the inner disks, give new constraints on the dark matter, but this time in the outer disks.
The Two Pattern Speeds of NGC 3359
Authors: BOONYASAIT VEERA , PATSIS P.A. , GOTTESMAN S T
Published: June 2005

Abstract: Using both observations and theoretical techniques, we show that the barred spiral galaxy NGC 3359 contains two pattern speeds. The faster pattern speed for the bar is obtained from isophotal analysis and stellar orbit theory. To explain the spiral arms and the observed velocity field of the disk, a slower pattern speed is required. Nonlinear resonance coupling is the supporting theory for the existence of two pattern speeds for the galaxy. The best match of our models with the observed data indicates a pattern speed for the bar of 39.17 km·sec−1∼kpc−1 and a value between 10 and 16 km·sec−1·kpc−1 for the spiral.
Evolution of Binary Supermassive Black Holes via Chain Regularization
Authors: SZELL ANDRAS , MERRITT DAVID , MIKKOLA SEPPO
Published: June 2005

Abstract: A chain regularization method is combined with special purpose computer hardware to study the evolution of massive black hole binaries at the centers of galaxies. Preliminary results with up to N= 0.26× 106 particles are presented. The decay rate of the binary is shown to decrease with increasing N, as expected on the basis of theoretical arguments. The eccentricity of the binary remains small.
Gravitomagnetic Field and Penrose Scattering Processes
Authors: WILLIAMS REVA KAY
Published: June 2005

Abstract: In this paper we present theoretical model calculations involving Monte Carlo computer simulations of Compton scattering and electroe‐positron (e−e+) pair production processes in the ergosphere of a supermassive rotating black hole. Particles from an accretion disk surrounding the rotating black hole fall into the ergosphere and are scattered by particles that are confined in equatorial and nonequatorial orbits. The energy‐momentum vectors are calculated for the scattered escaping particles. Particles escape with energies of about 3 GeV or greater. Importantly, these model calculations show that the Lense‐Thirring effect, that is, the dragging of local inertial frames into rotation, inside the ergosphere, caused by the angular momentum of the rotating black hole, results in a gravitomagnetic force being exerted on the scattered escaping particles. Effects of this force on the Penrose scattered particles are analyzed and discussed.
Self‐Gravity Driven Instabilities at Accelerated Interfaces
Authors: HUECKSTAEDT ROBERT M. , HUNTER JAMES H. , LOVELACE RICHARD V.E.
Published: June 2005

Abstract: Nonlinear hydrodynamic flows are ubiquitous in the interstellar medium (ISM). Such flows play an important role in shaping atomic and molecular clouds and determining the initial conditions for star formation. One mechanism by which nonlinear flows arise is the onset and growth of interfacial instabilities. Any interface of discontinuous density is subject to a host of instabilities, including Rayleigh‐Taylor, Kelvin‐Helmholtz, and Richtmyer‐Meshkov. As part of an ongoing study of structure formation in the ISM, Hunter, Whitaker, and Lovelace discovered an additional density interface instability. This instability is driven by self‐gravity and termed the self‐gravity interfacial instability (SGI). The SGI causes any displacement of the interface to grow on roughly a free‐fall time scale, even when the perturbation wavelength is much less than the Jeans length. Numerical simulations have confirmed the expectations of linear theory, including the near scale invariance of the growth rate. Here, we build upon previous work by considering an initial condition in which the acceleration due to self‐gravity is non‐zero at the interface.
Dynamics of Intracluster Gas and Bulk Motions in Clusters
Authors: DUPKE RENATO
Published: June 2005

Abstract: In this paper I briefly discuss progress in recent lines of research on the internal dynamics of clusters of galaxies that have been made possible thanks to improvements in current e‐ray spectrometers that enable them to perform detailed spatially resolved spectroscopy. In particular, I focus on the study of bulk motion in intracluster gas and the nature of features called cold fronts.
Resonance Bands and Binary‐Star Formation
Authors: LEBOVITZ NORMAN R.
Published: June 2005

Abstract: Numerical computations on the evolution of realistically stratified, asymmetric, sele‐gravitating masses reveal the onset of an instability that is suggestive of, but not decisive for, the formation of a binary star. On the other hand, analysis of the evolution and stability of idealized models consisting of uniform‐density ellipsoids has been qualitatively accurate in predicting certain features of the behavior of the more realistically stratified figures. This idealized theory is, therefore, reconsidered in an attempt to isolate additional qualitative features that may be common both to the idealized and to realistic figures, and therefore, serve not only as a guide in formulating issues to be addressed in numerical computations but also as a means of interpreting the outcomes of such calculations. Several such features are isolated in this paper, the most striking of which is the existence and importance of resonance bands of instability encountered by the evolutionary trajectories.
The Symplectic Group and Classical Mechanics
Authors: DRAGT ALEX J.
Published: June 2005

Abstract: The symplectic group is the underlying symmetry group for Hamiltonian dynamics. Yet relatively little is commonly known about its properties including its Lie structure and representations. This paper describes and summarizes some of these properties; and, as a first application of symplectic group theory, provides a symplectic classification of all firs–‐order differential equations in an even number of variables.
Chaos and Quantum Mechanics
Authors: HABIB SALMAN , BHATTACHARYA TANMOY , GREENBAUM BENJAMIN , JACOBS KURT , SHIZUME KOSUKE , SUNDARAM BALA
Published: June 2005

Abstract:The relationship between chaos and quantum mechanics has been somewhat uneasy—even stormy, in the minds of some people. However, much of the confusion may stem from inappropriate comparisons using formal analyses. In contrast, our starting point here is that a complete dynamical description requires a full understanding of the evolution ofmeasured systems, necessary to explain actual experimental results. This is of course true, both classically and quantum mechanically. Because the evolution of the physical state is now conditioned on measurement results, the dynamics of such systems is intrinsically nonlinear even at the level of distribution functions. Due to this feature, the physically more complete treatment reveals the existence of dynamical regimes—such as chaos—that have no direct counterpart in the linear (unobserved) case. Moreover, this treatment allows for understanding how an effective classical behavior can result from the dynamics of an observed quantum system, both at the level of trajectories as well as distribution functions. Finally, we have the striking prediction that time‐series from measured quantum systems can be chaotic far from the classical regime, with Lyapunov exponents differing from their classical values. These predictions can be tested in next‐generation experiments.
Application of infrared technology for quality control of diesel engine glow plugs
Authors: Al-Habaibeh A , Zorriassatine F , Parkin R M , Jackson M R
Published: June 2005

In recent years, the diesel engine has increasingly become a more popular choice with manufacturers and car buyers owing to its high fuel and power efficiencies. The research into diesel engine and its components is driven by the desire to meet strict emission standards and improving performance. This paper describes the application of infrared technology for quality control of diesel engine glow plugs. It is not sufficient to measure the resistance of glow plugs to assess their conformance to the performance specifications on account of the irregularity of the heat patterns produced. Moreover, the full power testing of glow plugs is not practical for quality control owing to the consumption of power, the considerable length of time, and the extreme temperatures generated. This paper describes a novel approach using low-cost infrared technology and a limited power-consuming experiment in order to test 100 per cent conformance of manufactured glow plugs. The results show that the technology can be utilized for quality control inspection of glow plugs.
Cutting force monitoring in the endmilling operation for chatter detection
Authors: Yoon M C , Chin D H
Published: June 2005

The chatter phenomenon shows the dynamic characteristics of tool vibration in the endmilling process and will change according to the irregular dynamic characteristics of that tool vibration. This chatter produces an adverse effect on tool life, machining integrity, surface quality of the workpiece, and other geometric accuracy. Chatter behaviour in endmilling is a complex, non-linear phenomenon, which is very difficult to detect and diagnose. It is therefore necessary to suggest a new method for analysing chatter mechanics. This paper presents a new method for the detection of chatter in the endmilling operation based on the wavelet transform. This wavelet transform method provides various ways to determine chatter characteristics. The fundamental coefficient property of the wavelet transform is reviewed. The reliability of the wavelet transform method is verified by comparing the spectra using the fast Fourier transform (FFT). The behaviour of the detail coefficients obtained by wavelet transform reveals the possibility to detect and analyse chatter and other malfunction states using tool dynamometer cutting force. Because wavelets are closely related to filter, the method presented in this paper can be applied to other real-time cutting force monitoring and analysis in a range of endmilling processes.
Application of rapid manufacturing techniques in support of maxillofacial treatment: Evidence of the requirements of clinical applications
Authors: Chandra A , Watson J , Rowson J E , Holland J , Harris R A , Williams D J
Published: June 2005

The concept of applying rapid manufacturing technology to maxillofacial treatment has been described previously; however, these reports did not take into account the practicality of its actual incorporation into clinical practice. Patents in the field are based on imaging techniques combined with rapid manufacturing, which theoretically lead to reconstruction of faces. Some cases studies reported have dealt with the manufacture of prostheses on the laboratory scale. Here two case studies are reported that used imaging and rapid manufacturing techniques for making an ear prosthesis and a burns mask for two patients. Laser scanning was chosen for imaging and Thermojet printing and fused deposition modelling for rapid manufacturing. Outcomes of the study were threefold: improvement in the process, improvement in patient care, and clinical application of existing technology to healthcare. With further research this technology may aid maxillofacial prosthetists in busy facial clinics, reduce patient clinic time, and improve the final product.
Prediction of the cutting tool edge position and orientation accuracy through error synthesis of spindle elements
Authors: Filho J M Crichigno , Teixeira C R , Schroeter R B
Published: June 2005

Achieving workpiece high accuracy at low cost is one of the greatest challenges in the machining industry. The runout of the cutting tool is prejudicial to precision machining, causing errors in the machined part, variation in the tool life, and premature tool breakage. This paper focuses on modelling the cutting tool edge position and orientation variations of a spindle system. This is a static approach based on the errors of the spindle elements. A kinematic model of the spindle/toolholder/cutting tool using homogeneous transformation matrices is first present. The model takes into account the runout and tilt errors of the spindle, the parts tolerances of the toolholder interfaces (spindle nose-toolholder and toolholder-cutting tool shank), as well as the cutting tool edge tolerance. The paper concludes with a simulation based on common values of the spindle elements. The proposed model is expected to provide insights into the advanced tolerance analysis of the spindle system.
Arc sensor model using multiple-regression analysis and a neural network
Authors: Kim Yongjae , Rhee Sehun
Published: June 2005

Experimental arc sensor models are developed by consideration of the welding conditions and characteristics of each welding process, and developing the model is significant because of its applicability to various welding environments. In this study, different types of regression model were developed for the current area difference method, the current integration difference method, and the weaving end current difference method, which are commonly used for the arc sensor. The characteristics of each regression model were examined, and a multiple-regression model was subsequently suggested, integrating all the conventional model characteristics. The multiple-regression model used the welding current signal of each model as the regressor and the offset distance as the response variable. In addition, an artificial neural network employing the current variable of each model as the input variable and the offset distance as the output variable was suggested as a new arc sensor model. A seam tracking simulation with a fuzzy controller implemented was constituted to facilitate the optimization of the scaling factor, and the scaling factor minimizing the tracking error was determined through the grid search method. Conventional models and the models suggested in this study were consequently compared with each other through the seam tracking experiment using the optimized scaling factors.
Static and dynamic analysis of a nanopositioning flexure-hinge stage with a flexible lever mechanism
Authors: Min Kyung S , Choi Woo C , Song Shin H , Hwang Eun J
Published: June 2005

A displacement magnifying mechanism is usually employed in a nanopositioning stage to achieve large stage motion. A lever mechanism is the most widely used displacement magnifying mechanism. This study proposes a more reasonable model including flexible levers to estimate the stiffness and displacement of the stage. This paper describes an analytic lever model and its experimental verification. Analytic and experimental results were very similar. The model proposed in this study can well predict the stage motions.
Ambiguous figure perception and theory of mind understanding in children with autistic spectrum disorders
Authors: Sobel David M. , Capps Lisa M. , Gopnik Alison
Published: June 2005

Researchers in early social‐cognition have found that the ability to reverse an ambiguous figure is correlated with success on theory of mind tasks (e.g. Gopnik & Rosati, 2001). The present experiment examined children with autistic spectrum disorders (ASD) without mental delay to see whether a similar relationship existed. Ropar, Mitchell, and Ackroyd (2003)demonstrated that children with ASD with mental delay were impaired on theory of mind tasks, but were as likely as mentally delayed controls to generate both interpretations of an ambiguous figure when informed of its ambiguity. The present study replicated this finding on children with ASD without mental delay. However, overall perception of ambiguous figures was different. These children were less likely to spontaneously generate both interpretations of the figure, and more likely to perseverate on a single interpretation than the comparison children. Like Ropar et al., we found no correlation between theory of mind and informed reversals, but spontaneous reversals were correlated with performance on an advanced theory of mind task. These data suggest that reversals of ambiguous figures are linked to higher‐level representational abilities, which might also be involved in social functioning, and impaired in children with ASD.
Children's understanding of their own and others' mental states. Part B. Understanding of others precedes self‐understanding for some false beliefs
Authors: Mitchell Robert W. , Neal Melissa
Published: June 2005

We examined 3‐ to 6‐year‐old children's understanding of their own and another's false beliefs in two experiments using diverse deceptive box and unexpected transfer tasks. Tasks in the first experiment required the child to think about an absent person's responses to questions, whereas those in the second experiment used a confederate present during testing. Children performed better on deceptive box tasks when the other person was present rather than absent; they performed equally on accidental and intentional unexpected transfer tasks. Children understood the other's false beliefs by 4–5 years of age, and their own by 5–6 years of age. Children aged between 4 and 5 years appear to have greater difficulty discounting or ignoring misleading information when thinking about their own beliefs than when thinking about another's, at least for the particular false belief tasks employed. Inconsistencies between our findings and those of a recent meta‐analysis (Wellman, Cross, & Watson, 2001) are easily reconciled.
Children's understanding of their own and others' mental states. Part A. Self‐understanding precedes understanding of others in pretence
Authors: Mitchell Robert W. , Neal Melissa
Published: June 2005

We examined 3‐ to 6‐year‐old children's attributions of pretence when their own or another's behaviours were characterized as similar (usually unintentionally) to that of a real or nonexistent animal. In some pretence tasks, we asked children if they were trying to look like or looked like the animal they were characterized as looking like; in others, if and how they could (or why they could not) pretend to be a real or nonexistent animal. Children at 4–6 years of age understood their own pretences better than another's pretences, but even by 6 years of age children continued to fail to understand pretence by another. Across ages children tended to be consistent in their claims about whether or not they looked liked (or were trying to look like) the animal, and whether or not they were pretending to be it. Children appear to take someone's merely looking like an animal as evidence that the person (whether self or other) is pretending to be that animal. Their success on self‐pretence tasks probably results from their unwillingness to believe that their own actions look like those of the animal because they had not intended to look like it.
The effect of simultaneous versus serial responding on children's ability to coordinate two dimensions
Authors: Cochran Jane M. A. , Davis Alyson
Published: June 2005

Previous research by Lidster and Bremner (1999) on young children's ability to coordinate two dimensions has shown that performance on construction tasks (in which children have to give the correct coordinates for a point in space that is already known) is superior to performance on interpretation tasks (in which children are given a pair of coordinates and have to locate the correct point in space on the basis of these). The present study investigates the suggestion made by Lidster and Bremner that construction tasks may be easier due to the possibility that they can be solved by attending to only one dimension at a time. In this experiment 84 children between the ages of 3 and 6 years were given 16 trials of a construction task, which they were either asked to do by moving two pointers simultaneously or by moving the pointers sequentially. Overall there was no main effect of condition. However, some trials were affected by condition. These results are discussed in relation to Lidster and Bremner's suggestions and Huttenlocher, Newcombe, and Sandberg's (1994) claims regarding the development of spatial understanding.
Minority children's intergroup attitudes about peer relationships
Authors: Margie Nancy Geyelin , Killen Melanie , Sinno Stefanie , McGlothlin Heidi
Published: June 2005

Intergroup attitudes were assessed in African‐American (N=70) and non‐African‐American minority (N=80) children, evenly divided by gender, in first (M=6.5 years old) and fourth (M=9.6 years old) grades attending mixed‐ethnicity public schools in a suburban area of a large mid‐Atlantic city in the USA. Children were interviewed to test hypotheses about implicit racial biases, perceptions of similarity between peer dyads, and judgments about cross‐race friendships. Implicit racial biases emerged when children evaluated ambiguous picture cards, with children viewing a White child as more likely to be a transgressor than a Black child in certain situations. There were no racial biases when evaluating potential cross‐race friendship (it was judged to be feasible); nor was there any evidence of an outgroup homogeneity effect. Children who used ethnicity as a reason for judging peers to be similar, however, were less likely to judge that the cross‐race dyads could be friends. The findings indicate the ways in which minority children's judgments about the majority and their perceptions of similarity between peer dyads influence their interpretations of peer interactions.
European‐American children's intergroup attitudes about peer relationships
Authors: McGlothlin Heidi , Killen Melanie , Edmonds Christina
Published: June 2005

Intergroup attitudes were assessed in European‐American first grade (M=6.8 years) and fourth grade (M=9.9 years) boys and girls (N=94) to test hypotheses about implicit racial biases, perceptions of similarity between peer dyads, and judgments about cross‐race friendships. Two assessments, an ambiguous situations task and a perceptions of similarity task, were administered to all participants. Contrary to prior findings, participants did not display implicit racial biases when interpreting children's intentions to commit a negative moral transgression towards a peer. Implicit biases were revealed, however, when asking children to judge cross‐race friendship potential. The findings on children's similarity perceptions revealed that children focused on shared interests and race when judging similarity. Given that previous meta‐analyses of prejudice have pointed to cross‐race friendships as a significant predictor of a reduction in prejudice, these findings help to understand what may account for the relative infrequency of intergroup friendships in childhood. Further, the findings indicate the ways in which, implicit racial biases influence friendship decisions.
Construction and validation of a children's interpersonal trust belief scale
Authors: Rotenberg Ken J. , Fox Claire , Green Sarah , Ruderman Louise , Slater Kevin , Stevens Kelly , Carlo Gustavo
Published: June 2005

A scale was constructed to assess children's generalized trust beliefs (CGTB) in four target groups (mother, father, teacher and peer) with respect to three bases of trust: reliability, emotionality, and honesty. The CGTB Scale was administered to 145 Year 5 and 156 Year 6 children (mean age = 10 years, 1 month) residing in the English Midlands, United Kingdom. Exploratory and confirmatory factor analyses yielded evidence for the expected factor structure of the CGTB Scale. The total CGTB Scale and subscales demonstrated acceptable internal consistency and expected levels of stability across time. As support for validity, Year 6 participants' scores on the CGTB peer subscale were correlated with their trust beliefs in classmates, assessed a year earlier. As hypothesized, children's helpfulness to their classmates was correlated with the CGTB Scale and subscales. Girls displayed greater trust beliefs and helpfulness to classmates than did boys.
Children and mothers drawing together: Encountering graphic conventions during social interactions
Authors: Braswell Gregory S. , Rosengren Karl S.
Published: June 2005

A recent graphic schemas account of drawing development that emphasizes the appropriation of graphic conventions has provided an alternative to constructivist theories, which have viewed development as a progression through universal stages. The present study addresses the limitations of this account by investigating younger children than have usually been studied, and by examining specific behaviours that may contribute to the appropriation of drawing conventions during mother–child social interaction. Toddlers and their mothers participated in an open‐ended drawing task and a structured copying task. Mothers also completed a questionnaire regarding their beliefs about drawing. Variations in dyadic interactions were related to children's ages, task constraints, and maternal beliefs about drawing development. For example, older children and their mothers used semantics‐related speech to a greater extent than younger children and their mothers. Some behaviours were more prevalent during the open‐ended task (maternal assistance), and others were more prevalent during the structured task (e.g. maternal demonstrations). Several maternal behaviours also varied according to mothers' beliefs about drawing development.