bluuebunny/crossref_metadata_2025_split huggingface dataset:
Statistical structure of self-sustaining attached eddies in turbulent channel flow
Authors: Hwang Yongyun 
Published: February 2015

AbstractThe linear growth of the spanwise correlation length scale with the distance from the wall in the logarithmic region of wall-bounded turbulent flows has been understood as a reflection of Townsend’s attached eddies. Based on this observation, in the present study, we perform a numerical experiment, which simulates energy-containing motions only at a given spanwise length scale in the logarithmic region, using their self-sustaining nature found recently. The self-sustaining energy-containing motions at each of the spanwise length scales are found to be self-similar with respect to the given spanwise length. Furthermore, their statistical structures are consistent with those of the attached eddies in the original theory, providing direct evidence on the existence of Townsend’s attached eddies. It is shown that a single self-sustaining attached eddy is composed of two distinct elements, one of which is a long streaky motion reaching the near-wall region, and the other is a relatively short vortical structure carrying all the velocity components. For the given spanwise length ${\it\lambda}_{z}$ between ${\it\lambda}_{z}^{+}=100$ and ${\it\lambda}_{z}\simeq 1.5h$, where $h$ is half the height of the channel, the former is found to be self-similar along $y\simeq 0.1{\it\lambda}_{z}$ and ${\it\lambda}_{x}\simeq 10{\it\lambda}_{z}$, while the latter is self-similar along $y\simeq 0.5{\it\lambda}_{z}\sim 0.7{\it\lambda}_{z}$ and ${\it\lambda}_{x}\simeq 2{\it\lambda}_{z}\sim 3{\it\lambda}_{z}$ where $y$ is the wall-normal direction. The scaling suggests that the smallest attached eddy would be a near-wall coherent motion in the form of a streak and quasi-streamwise vortices aligned to that, whereas the largest one would be an outer motion with a very-large-scale motion (VLSM) and large-scale motions (LSMs) aligned to that. The attached eddies in between, the size of which is proportional to their distance from the wall, contribute to the logarithmic region and fill the space caused by the length scale separation. The scaling is also found to yield behaviour consistent with the emergence of $k_{x}^{-1}$ spectra in a number of previous studies. Finally, a further discussion is provided, in particular on Townsend’s inactive motion and several recent theoretical findings.
Centre-manifold reduction of bifurcating flows
Authors: Carini M. , Auteri F. , Giannetti F. 
Published: February 2015

AbstractIn this paper we describe a general and systematic approach to the centre-manifold reduction and normal form computation of flows undergoing complicated bifurcations. The proposed algorithm is based on the theoretical work of Coullet & Spiegel (SIAM J. Appl. Maths, vol. 43(4), 1983, pp. 776–821) and can be used to approximate centre manifolds of arbitrary dimension for large-scale dynamical systems depending on a scalar parameter. Compared with the classical multiple-scale technique frequently employed in hydrodynamic stability, the proposed method can be coded in a rather general way without any need to resort to the introduction and tuning of additional time scales. The method is applied to the dynamical system described by the incompressible Navier–Stokes equations showing that high-order, weakly nonlinear models of bifurcating flows can be derived automatically, even for multiple codimension bifurcations. We first validate the method on the primary Hopf bifurcation of the flow past a circular cylinder and after we illustrate its application to a codimension-two bifurcation arising in the flow past two side-by-side circular cylinders.
Combustion enhancement in a scramjet engine using oxygen enrichment and porous fuel injection
Authors: Capra Bianca R. , Boyce R. R. , Kuhn M. , Hald H. 
Published: February 2015

AbstractThis paper reports on the experimental testing of oxygen-enriched porous fuel injection in a scramjet engine. Fuel was injected via inlet mounted, oxide-based ceramic matrix composite (CMC) injectors on both flow path surfaces that covered a total of 9.2 % of the intake surface area. All experiments were performed at an enthalpy of $3.93{-}4.25\pm 3.2\,\%~\text{MJ}~\text{kg}^{-1}$, flight Mach number 9.2–9.6 and an equivalence ratio of $0.493\pm 3\,\%$. At this condition, the engine was shown to be on the verge of achieving appreciable combustion. Oxygen was then added to the fuel prior to injection such that two distinct enrichment levels were achieved. Combustion was found to increase, by as much as 40 % in terms of combustion-induced pressure rise, over the fuel-only case with increasing oxygen enrichment. Further, the onset of combustion was found to move upstream with increasing levels of oxygen enrichment. Thrust, both uninstalled and specific, and specific impulse were found to be improved with oxygen enrichment. Enhanced fuel–air mixing due to the pre-mixing of oxygen with the fuel together with the porous fuel injection are believed to be the main contributors to the observed enhanced performance of the tested engine.
Interacting vorticity waves as an instability mechanism for magnetohydrodynamic shear instabilities
Authors: Heifetz E. , Mak J. , Nycander J. , Umurhan O. M. 
Published: February 2015

AbstractThe interacting vorticity wave formalism for shear flow instabilities is extended here to the magnetohydrodynamic (MHD) setting, to provide a mechanistic description for stabilising and destabilising shear instabilities by the presence of a background magnetic field. The interpretation relies on local vorticity anomalies inducing a non-local velocity field, resulting in action at a distance. It is shown here that the waves supported by the system are able to propagate vorticity via the Lorentz force, and waves may interact. The existence of instability then rests upon whether the choice of basic state allows for phase locking and constructive interference of the vorticity waves via mutual interaction. To substantiate this claim, we solve the instability problem of two representative basic states, one where a background magnetic field stabilises an unstable flow and the other where the field destabilises a stable flow, and perform relevant analyses to show how this mechanism operates in MHD.
International investment decisions under uncertainty: Contributions of real options theory and future directions
Authors: Song Sangcheol , Makhija Mona , Kim Sung Min 
Published: February 2015

AbstractWe undertake a critical literature review to facilitate academic dialogs regarding decisions under uncertainty in international business settings and highlight the growing focus on international investments as conveyers of real options. Our literature review (1) provides a systematic overview of uncertainty types considered in this literature, real options identified as particular to international investments, and valuation approaches used and (2) highlights key methodological approaches used for testing real options models applied to international investments, and the controversies in this regard. This study draws on the above to shed light on important avenues for future research including (a) the need for more fine-grained and diverse measures of uncertainty in the international context, (b) an emphasis on clarifying the value effects of combinations of real options, and (c) the necessity of further consideration of the costs of options along with the value.
Will Raman meet bacteria on Mars? An overview of the optimal Raman spectroscopic techniques for carotenoid biomarkers detection on mineral backgrounds
Authors: Hooijschuur J.H. , Verkaaik M.F.C. , Davies G.R. , Ariese F. 
Published: February 2015

AbstractRaman spectroscopy appears to be an ideal technique for the initial detection of biomarkers, molecules that are potentially indicative of life on planetary bodies elsewhere in our solar system. Carotenoids are particularly useful biomarkers as they are used widely across the species, relatively resistant to breakdown and no inorganic source is known. They are used by microorganisms in their cell membranes for protection against UV radiation. In this paper we focus on the detection of carotenoids in microorganisms within a mineral matrix. We compare the Raman signatures of pure compounds with those of laboratory-made mixtures of β-carotene and minerals. Carotenoids covered by 2.5 mm of translucent calcite or 40 mm of transparent halite were detected using a conventional confocal Raman microscope. To improve sensitivity and hence detection levels, Raman measurements were successfully performed under resonant conditions. Raman analysis can be compromised by fluorescence interference. Data are presented to show how the contribution from the fluorescent background in the Raman spectra can be reduced when making use of gated detection in time-resolved Raman spectroscopy. Overall, this study demonstrates some of the potential of Raman spectroscopy as a method for the detection of (past) life signatures during future planetary missions without taking current technical limitations such as instrumental size into account as recent rapid technical developments suggest these limitations will be resolved in time.
Factorial graphical models for dynamic networks
Authors: WIT ERNST , ABBRUZZO ANTONINO 
Published: February 2015

AbstractDynamic network models describe many important scientific processes, from cell biology and epidemiology to sociology and finance. Estimating dynamic networks from noisy time series data is a difficult task since the number of components involved in the system is very large. As a result, the number of parameters to be estimated is typically larger than the number of observations. However, a characteristic of many real life networks is that they are sparse. For example, the molecular structure of genes make interactions with other components a highly-structured and, therefore, a sparse process. Until now, the literature has focused on static networks, which lack specific temporal interpretations.We propose a flexible collection of ANOVA-like dynamic network models, where the user can select specific time dynamics, known presence or absence of links, and a particular autoregressive structure. We use undirected graphical models with block equality constraints on the parameters. This reduces the number of parameters, increases the accuracy of the estimates and makes interpretation of the results more relevant. We illustrate the flexibility of the method on both synthetic and real data.
Identifying high-value areas to strengthen marine conservation in the channels and fjords of the southern Chile ecoregion
Authors: Vila Alejandro R. , Falabella Valeria , Gálvez Mauricio , Farías Aldo , Droguett Daniela , Saavedra Bárbara 
Published: February 2015

AbstractAlthough Chile has been establishing marine protected areas since the 1960s, studies to identify representative areas for marine biodiversity conservation at the ecoregional scale are lacking. Using theMarxandecision support tool we conducted a systematic planning process to identify High Conservation Value Areas in the channels and fjords of the southern Chile ecoregion. We involved 74 experts and other stakeholders in identifying conservation features, setting targets and compiling distribution data. Current distributions of 39 features were used inMarxananalyses. In one scenario we locked planning units that contained the Francisco Coloane Marine Protected Area. In a second scenario we also excluded planning units that overlapped with Appropriate Areas for Aquaculture, defined by the Chilean government's coastal zoning process. One-hundred percent of the proposed conservation targets were met in both scenarios. Although the distribution of 12 conservation features overlapped to a certain extent (>10%) with Appropriate Areas for Aquaculture,Marxanidentified conservation solutions avoiding these areas. Our suggested portfolio of High Conservation Value Areas comprises a network of 33 sites, covering 99,432 km2(12% of the ecoregion). These results provide the first science-based roadmap for decision makers and conservationists, and were used by the Chilean government in its coastal zoning process to define priority areas for conservation. Consequently, salmon farming has been excluded from Tierra del Fuego island.
Families, Prestige Goods, Warriors & Complex Societies: Beaker Groups of the 3rd Millennium calBCAlong the Upper & Middle Danube
Authors: Heyd Volker 
Published: February 2015

From the Middle Copper Age in the mid-4th millennium calBC, and throughout the whole Late Copper Age, we observe the emergence of supra-regional, expansionistic ‘cultures’. Originating in south-east Europe, they expanded into central and northern Europe, eventually reaching the west and the margins. Typical of these are the Černavoda III/Boleráz cultures; then, later, the Baden sequence, along with the Globular Amphora Culture adjacent to the northern arc of the Carpathian mountains. The Corded Ware/Single Grave Cultures, and finally the Bell Beaker Culture, follow in a third stage from the first quarter of the 3rd millennium calBC. The latter expand – emerging from the Iberian Peninsula according to current research – towards the east in a fourth stage, reaching Britain and Ireland, Central Europe, and the central Mediterranean by 2500 calBC. It is now common knowledge that this Bell Beaker phenomenon does not represent a homogeneous unit, but splits into at least four supra-regional groupings. Of these, the Central European, or Bell Beaker East Group, is the focus of this study.The many published and well-dated assemblages along the Danube between southern Germany and western Hungary, and also in the Czech Republic, allow us to pose questions concerning the social organisation of these Beaker societies. Extended families, without visible hierarchies between them, are mirrored in cemeteries as the basic social unit. The settlement pattern seems to consist of single farmsteads, often closely spaced and each inhabited by one of these extended families. As self-sufficient, but flexibly organised and already partly specialised economic units, they demonstrate an equal exchange of information, goods, genes, and social values. Existing fundamental hierarchies within these families are demonstrated, however, by unequal burial customs, in particular the inclusion of prestige objects in some graves, and by some lavishly equipped child burials of both sexes, as well as in the portrayal of some individuals in death as hunters or warriors, buried with archery equipment.Bell Beaker society displays an intermediate position between ranked and stratified societies, with signs that it was evolving towards simple chiefdoms. However, this stage of social organisation is only fully reached in Central Europe during the second half of the Early Bronze Age, from 2000 calBConwards.
A Late Neolithic Palisaded Enclosure at Marne Barracks, Catterick, North Yorkshire
Authors: Hale Duncan , Platell Andy , Millard Andrew 
Published: February 2015

An open-area excavation conducted in advance of development at Marne Barracks, Catterick, in 2004 identified a relatively rare Late Neolithic ‘palisaded’ enclosure and other features. Approximately 55% of the enclosure was exposed. It consisted of two concentric sub-circular palisades with diameters up to 175 m and 200 m respectively. Each palisade consisted of a double circuit of posts, with the posts being c. 1 m apart from centre to centre. Many of the posts on the western side of the monument had been sufficiently carbonised for the remains of individual posts to be identifiable. Twenty-one radiocarbon ages were determined and Bayesian modelling has produced a date estimate of 2530–2310 cal BC for the start of construction of the monument. This date matches well with new dates for the construction of Silbury Hill, the appearance of Beaker pottery in graves, the Amesbury Archer, and the timber circles at Durrington Walls, for example.The Marne Barracks monument exhibits significant differences to other known examples of this type, and is in some respects unique. In particular the ‘paired post’ arrangement of a double circuit of posts in each palisade is unparalleled in any other known example. The apparent width of the entrances to the Marne enclosure is also at variance with other known sites, though this may in part be an artefact of post-depositional survival. The monument sits in a ritual landscape and, like a few others of its type, is close to water and a hill or large mound from where the activities taking place within the enclosure might have been observed. Do the nearby hill, the entrances, and the arrangement of the uprights all relate to control of physical and visual access into, or out of, the monument?A number of broadly contemporary monuments, all within 5 km of Marne Barracks, contribute to a significant Neolithic ritual focus on the River Swale gravels. The complex of cursus and henge monuments at Thornborough and the henges at Nunwick, Hutton Moor, and Cana Barn all lie less than 25 km to the south, in the Swale-Ure interfluve.
The Lower Palaeolithic Industry from Azé Cave (Saône et Loire) France: a case study of an assemblage without any handaxes
Authors: Moncel Marie-Hélène , Gaillard Claire , Combier Jean 
Published: February 2015

The Azé Cave (Sâone-et-Loire, France) has yielded, among other archaeological and palaeontological remains, a Lower Palaeolithic industry within a layer dated through faunal remains to 400–350 kya. This industry is made up of local rocks, mostly poor quality flint, and also chert and crystalline rocks.Only flint was definitely knapped; chert was only broken into pieces before being used. The process of knapping is opportunistic and the cores, seldom exhausted, usually bear two opposite reduction faces. The flakes often reveal patches of residual cortex. They are moderately thick and the striking platform angle varies within a wide range of values. Some of them seem to be the result of a tearing-off motion. All the flint pieces have been heavily retouched; half of them have been simply utilised, others are proper tools, mostly scrapers, usually with steep retouch. Fragments of chert, sometimes obtained by tearing-off (from the cave walls?) have been often retouched but with less intensity than the flint. A good number of more or less trimmed cobbles are also part of this collection. However, handaxes are completely missing.The lithic industry of Azé 1–1 lacks standardisation for the core reduction process as well as for trimming or retouching. It fits well in the Lower Palaeolithic industry but the absence of handaxes is noteworthy. This industry offers one more contribution to the diversity of this cultural period.
Palaeolithic Archaeology at the Swan Valley Community School, Swanscombe, Kent
Authors: Wenban-Smith Francis , Bridgland David , Parfitt Simon , Haggart Andrew , Rye Phillip 
Published: February 2015

This paper reports on the recovery of Palaeolithic flint artefacts and faunal remains from fluvial gravels at the base of a sequence of Pleistocene sediments revealed during construction works at two sites to the south of Swanscombe village, Kent. Although outside the mapped extent of the Boyn Hill/Orsett Heath Formation, the newly discovered deposits can be firmly correlated with the Middle Gravels and Upper Loam from the Barnfield Pit sequence dating to c. 400,000–380,000 BP. This increases greatly the known extent of these deposits, one horizon of which produced the Swanscombe Skull, and has provided more information on their upper part.Comparison of the lithic assemblages from volume-controlled sieving with those from general monitoring demonstrated that artefact collections formed without controlled methods of recovery, such as form the majority of the Lower and Middle Palaeolithic archaeological record, are likely to be disproportionately dominated by larger, more visible, and more collectable neatly-made handaxes to the detriment of more poorly made, asymmetrical handaxes and cores, flakes, and percussors. The lithic assemblage from the fluvial gravel was confirmed as dominated by pointed handaxes, supporting previous studies of artefacts front the equivalent Lower Middle Gravel at Barnfield Pit. The raw material characteristics of the assemblage were investigated, and it was concluded that there was no indication that the preference for pointed shapes could be related to either the shape or source of raw material.This paper also reviews the significance of lithic assemblages from disturbed fluvial contexts, and concludes that, contrary to some current perspectives, they have a valuable role to play complementing less disturbed evidence in developing understanding of the Palaeolithic.
Power Pulses Across a Cultural Divide: Cosmologically Driven Acquisition Between Armorica and Wessex
Authors: Needham Stuart P. 
Published: February 2015

Understanding of the nature and significance of connections between Armorica and southern Britain in the Early Bronze Age has been inhibited by poorly refined chronologies. The Armorican grave series is now believed to span seven to eight centuries (c. 2300/2200–1500 BC) and association patterns are used to suggest five assemblages (series 1–5). In the absence of many skeletal remains, structural and organisational evidence is gleaned to suggest that some tombs were not immutably sealed and were used more than once. It is suggested that the accumulation of successive grave groups, primarily in series 2 and 4, is one factor blurring signs of chronological progression, whilst added complexity derives from regional shifts.A review of specific artefact types and burial rites on the two sides of the western Channel gives little credence to the migration of more than occasional individuals. On the contrary, an essential autonomy in the way that materials and artefacts are employed by elites comes through, yet this is set against some important material connections. The conundrum is resolved by suggesting that inter-dependence was actually limited and that the procurement of exotic materials/goods was driven by ‘cosmological acquisition’ needs which, if anything, maintained real differences between distant participating societies. In Wessex, however, the growth of this mode of extracting ideological capital from long-range contacts was to have profound consequences for superordinate centres based around Late Neolithic ceremonial complexes – their ultimate transformation and eclipse.
Ground Stone Tools from Serra Orlando (Morgantina) and Stone Axe Studies in Sicily and Southern Italy
Authors: Leighton Robert , Dixon J. E. , Duncan A. M. 
Published: February 2015

Ground and polished stone axes in southern Italy received little attention after a period of lively interest in the late 19th century. The great number of axes from archaeological sites and collections suggests widespread manufacture and exchange on a considerable scale. In eastern Sicily the production of basalt axes was long-lived, beginning in the Neolithic (Stentinello phase) and reaching a peak in the Copper and Early Bronze Ages. Greenstone axes are also found throughout these periods. By the Middle or Late Bronze Age, stone axes were probably little used, having been largely replaced by metal tools.The axes from Serra Orlando (where the historical site of Morgantina is located) form one of the largest collections in Sicily from a single site, where they were found in multi-period contexts, dating from the third millennium BC until the Hellenistic period. Petrological analysis suggests that basalt from the Iblean hills was frequently used for their manufacture, while the serpentinites, tremolite-bearing rocks and pyroxenite probably originate in the Calabro-Peloritani Arc. The results of the analysis of thin sections are presented in appendixes. Raw materials, distribution and manufacture of axes are discussed and a preliminary investigation of their typology is presented. Multiple functions for Sicilian axes, related to morphology and raw materials, are suggested by their archaeological contexts.