Showing papers by "King's College, Aberdeen published in 2008"
TL;DR: It is hypothesized that the synchronization of movements during a dyadic interaction may prompt increased attention to be directed to an interaction partner, hence facilitate the information that participants glean during a social exchange, and the results supported this prediction.
163 citations
TL;DR: Different bifurcation scenarios under varying the excitation frequency near grazing are shown for a number of values of the excited amplitude and a good correspondence between them is shown for different stiffness ratios.
Abstract: In this paper, extensive experimental investigations of an impact oscillator with a one-sided elastic constraint are presented. Different bifurcation scenarios under varying the excitation frequency near grazing are shown for a number of values of the excitation amplitude. The mass acceleration signal is used to effectively detect contacts with the secondary spring. The most typical recorded scenario is when a non-impacting periodic orbit bifurcates into an impacting one via grazing mechanism. The resulting orbit can be stable, but in many cases it loses stability through grazing. Following such an event, the evolution of the attractor is governed by a complex interplay between smooth and non-smooth bifurcations. In some cases, the occurrence of coexisting attractors is manifested through discontinuous transition from one orbit to another through boundary crisis. The stability of non-impacting and impacting period-1 orbits is then studied using a newly proposed experimental procedure. The results are compared with the predictions obtained from standard theoretical stability analysis and a good correspondence between them is shown for different stiffness ratios. A mathematical model of a damped impact oscillator with one-sided elastic constraint is used in the theoretical studies.
124 citations
TL;DR: In this paper, the limit case of the SD (smooth and discontinuous) oscillator is studied and the system exhibits standard dynamics governed by the hyperbolic structure associated with the stationary state of the double-well.
Abstract: In this paper, the limit case of the SD (smooth and discontinuous) oscillator is studied. This system exhibits standard dynamics governed by the hyperbolic structure associated with the stationary state of the double-well. The substantial deviation from the standard dynamics is the non-smoothness of the velocity in crossing from one well to another, caused by the loss of local hyperbolicity due to the discontinuity. Without dissipation, the KAM structure on the Poincare section is constructed with generic KAM curves and a series of fixed points associated with surrounded islands of quasi-periodic orbits and the chaotic connection orbits. It is found that, for a fixed set of parameters, a special chaotic orbit exits there which fills a finite region and connects a series of islands dominated by different chains of fixed points. As one adds weak dissipation, the periodic solutions in this finite region remain unchanged while the quasi-periodic solutions (isolated islands) are converted to the corresponding periodic solutions. The relevant dynamics for the system with weak dissipation under external excitation is shown having period doubling bifurcation leading to chaos, and multi-stable solutions.
98 citations
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TL;DR: In this article, a tensor product theorem for stable modules with simple modules was proved for polynomial rings and over graded exterior algebras, where the use of cyclic shifted subgroups was avoided.
Abstract: We classify localising subcategories of the stable module category of a finite group that are closed under tensor product with simple (or, equivalently all) modules. One application is a proof of the telescope conjecture in this context. Others include new proofs of the tensor product theorem and of the classification of thick subcategories of the finitely generated modules which avoid the use of cyclic shifted subgroups. Along the way we establish similar classifications for differential graded modules over graded polynomial rings, and over graded exterior algebras.
92 citations
TL;DR: An architectural hierarchy of clastic sills is recognized in the Panoche giant injection complex in which staggered, stepped with erosive top surfaces, and multi-layered geometries occur in that stratigraphic order upward as mentioned in this paper.
Abstract: An architectural hierarchy of clastic sills is recognized in the Panoche Giant Injection Complex in which staggered, stepped with erosive top surfaces, and multi-layered geometries occur in that stratigraphic order upward. Genetic relationships between parent depositional sand bodies, the sand injections, a zone of hydraulic fracture and a palaeo sea floor are seen at a scale previously observed only by using seismic data. Sills and randomly oriented dykes intrude into a hydraulically fractured shale unit above and below which dykes predominate. Erosive surfaces (scallops) are identified on sills that, along with smaller erosional features, record low-viscosity turbulent flow during sand injection. Sand extrusions occur where dykes reach the palaeo sea floor.
70 citations
TL;DR: The Stac Fada Member of the Precambrian Stoer Group in Scotland has been interpreted as having an impact origin this paper, and the ejecta blanket reaches >20 m in thickness and contains abundant dark green, vesicular, devitrified glass fragments.
Abstract: Ejecta blankets around impact craters are rarely preserved on Earth. Although impact craters are ubiquitous on solid bodies throughout the solar system, on Earth they are rapidly effaced, and few records exist of the processes that occur during emplacement of ejecta. The Stac Fada Member of the Precambrian Stoer Group in Scotland has previously been described as volcanic in origin. However, shocked quartz and biotite provide evidence for high-pressure shock metamorphism, while chromium isotope values and elevated abundances of platinum group metals and siderophile elements indicate addition of meteoritic material. Thus, the unit is reinterpreted here as having an impact origin. The ejecta blanket reaches >20 m in thickness and contains abundant dark green, vesicular, devitrified glass fragments. Field observations suggest that the deposit was emplaced as a single fluidized flow that formed as a result of an impact into water-saturated sedimentary strata. The continental geological setting and presence of groundwater make this deposit an analogue for Martian fluidized ejecta blankets.
64 citations
TL;DR: Petrographic and fluid inclusion micro-thermometric study was performed on sandstones from the Devonian-Carboniferous reservoir rocks of the Clair Field, west of Shetland as discussed by the authors.
54 citations
01 Sep 2008
TL;DR: A summary of recently reported research in the area of Underwater Optics and Vision can be found in this article, which briefly covers advances in the following areas: (1) Image formation and image processing methods; (2) Extended range imaging techniques; (3) Imaging using spatial coherency (e.g. holography); and (4) Multiple-dimensional image acquisition and imageprocessing.
Abstract: Obtaining satisfactory visibility of undersea objects has been historically difficult due to the absorptive and scattering properties of seawater. Mitigating these effects has been a long term research focus, but recent advancements in hardware, software, and algorithmic methods have led to noticeable improvement in system operational range. This paper is intended to provide a summary of recently reported research in the area of Underwater Optics and Vision and briefly covers advances in the following areas: (1) Image formation and image processing methods; (2) Extended range imaging techniques; (3) Imaging using spatial coherency (e.g. holography); and (4) Multiple-dimensional image acquisition and image processing.
49 citations
TL;DR: In this paper, an experimental study and mathematical modelling of newly designed vibro-impact moling rig are presented, which is based on electro-mechanical interactions of a conductor with an oscillating magnetic field.
Abstract: In this paper experimental study and mathematical modelling of newly designed vibro-impact moling rig are presented. The design is based on electro-mechanical interactions of a conductor with an oscillating magnetic field. The rig consists of a metal bar placed within a solenoid which is connected to an RLC circuit, and an obstacle block positioned nearby. Both the solenoid and the block are attached to a base board. Externally supplied alternating voltage causes the bar to oscillate and hit the block resulting in the forward motion of the base board mimicking a mole penetration through the soil. By varying the excitation voltage and the capacitance in the circuit, a variety of system responses can be obtained. In the paper the rig design and experimental procedure are explained in detail, and the mathematical modelling of the rig is described. Then the obtained coupled electro-mechanical equations of motion are integrated numerically, and a comparison between experimental results and numerical predictions is presented.
40 citations
TL;DR: In this article, the impact of volcanic outgassing on plant communities within a large igneous province (LIP) was investigated and it was suggested that there may have been significantly elevated levels of P within the lava field proximal to the source vents, a distribution mirrored by Ca and Mg.
Abstract: Research from biological and geological sources has highlighted the role of volcanoes in the outgassing of P, and thermal fixation and subsequent atmospheric oxidation of NO x in volcanic environments. The impact of these nutrient fluxes on biological systems has been demonstrated on present-day Hawai9i, and here we consider the impact on the plant communities within a large igneous province (LIP). The Miocene Columbia River Basalt Province, the youngest LIP on Earth, contains many sedimentary interbeds between the flows of the major extrusive phase, and these interbeds preserve variable but often diverse palynofloras. By integration of palynofloral analysis with analysis of macronutrient levels in the interbeds it can be suggested that there may have been significantly elevated levels of P within the lava field proximal to the source vents, a distribution mirrored by Ca and Mg. Evidence for potential volcanogenic eutrophication is restricted to >10 3 year duration interbeds, contemporary with eruptive activity elsewhere in the LIP. The geochemistry and palynology of other interbeds demonstrate nutrient deficiency, with a potential route to nutrient sufficiency available from long-term symbiotic N-fixation. Elsewhere within the Columbia River Basalt Province, this process is short-circuited by the imput of felsic ash from the nearby Cascades Range of volcanoes.
31 citations
TL;DR: A case study of the implementation of a flexible learner-centred programme of study which blends face-to-face and online learning and the results of an investigation to explore their experiences of facilitation are presented.
Abstract: This paper presents a case study of the implementation of a flexible learner-centred programme of study which blends face-to-face and online learning. The programme was developed to be flexible in terms of content and study strategies, whilst remaining within more rigid organisational structures and processes. This paper outlines the programme and presents the model developed for flexible content delivery. The programme has been delivered simultaneously by five tutors to six groups of learners. Tutors drew on varying personal experiences of flexible and online learning and this paper also presents the results of an investigation to explore their experiences of facilitation. The findings provide a unique insight into the implications of such a programme for educators. Data were gathered using methods to promote and structure reflections on practice. Issues of relevance for others considering the development of flexible learner-centred programmes of study are presented.
TL;DR: In a series of experiments the pyrolytic effects of the heating induced during the hypervelocity impact (HVI) of small projectiles of high TOC mudrock were observed as discussed by the authors.
TL;DR: In this paper, a linear crack under an oblique time-harmonic wave is solved by the method of boundary integral equations, and the effect of friction governed by the Coulomb friction law is incorporated into the analysis.
TL;DR: In this paper, the fracture dynamic problems for elastic cracked solids with allowance for crack faces contact interaction were considered and the contact forces and the displacement discontinuity of the crack faces were studied.
TL;DR: The ontogenetic relationships between them are investigated, indicating that loss of the keel was a selective advantage that enabled those rotaliporids to remain in the surface water, thereby avoiding the expansion of the oxygen minimum zone.
TL;DR: In this paper, large-scale deformation structures in late Permian aeolian dune sands are associated with sand fluidization and injection Exceptional precipitation and flooding of the desert margin are believed to have caused mass-wasting by gravitational collapse and sliding of water-saturated dunes, which loaded down-dip strata, thus generating overpressure and triggering sand injection
Abstract: Large-scale deformation structures in late Permian aeolian dune sands are associated with sand fluidization and injection Exceptional precipitation and flooding of the desert margin are believed to have caused mass-wasting by gravitational collapse and sliding of water-saturated dunes, which loaded down-dip strata, thus generating overpressure and triggering sand injection This short-lived but heavy precipitation seems to have been associated with a climatic change from arid Rotliegend dune deposition to widespread Zechstein marine conditions within the greater North Sea area, probably just before or coinciding with deposition of the rapidly expanding marine Kupferschiefer
TL;DR: In this article, it was shown that a stabilised version of a C*-algebra A = sup n L(M n (A)) depends only on the primitive ideal space Prim(A).
Abstract: We consider the natural contraction from the central Haagerup tensor product of a C*-algebra A with itself to the space of completely bounded maps CB(A) on A and investigate those A where there exists an inverse map with finite norm L(A). We show that a stabilised version L'(A) = sup n L(M n (A)) depends only on the primitive ideal space Prim(A). The dependence is via simplicial complex structures (defined from primal intersections) on finite sets of primitive ideals that contain a Glimm ideal of A. Moreover L'(A) = L(A ⊗ K(H)), with K(H) the compact operators, which requires us to develop the theory in the context of C*-algebras that are not necessarily unital.
TL;DR: Bremke and Xi as discussed by the authors showed that the lowest two-sided cell for affine Weyl groups with unequal parameters consists of at most |W 0| left cells where W 0 is the associated finite Weyl group.
Abstract: Bremke and Xi determined the lowest two-sided cell for affine Weyl groups with unequal parameters and showed that it consists of at most |W_{0}| left cells where W_{0} is the associated finite Weyl group. We prove that this bound is exact. Previously, this was known in the equal parameter case and when the parameters were coming from a graph automorphism. Our argument uniformly works for any choice of parameters.
TL;DR: In this paper, the dynamic behavior of an impact oscillator with an SMA constraint has been modelled and analyzed, and it was found that low amplitude regimes are not affected by the presence of SMA element, while for the large amplitude responses a significant vibration reduction was achieved due to the phase transformations.
Abstract: The dynamic behaviour of an impact oscillator with an SMA constraint has been modelled and analysed. Following the formulation proposed by Bernardini and his co-authors [1,2] describing thermo-mechanics of SMA elements, we obtain a compact thermo-mechanical model of an impact pseudoelastic oscillator. Due to the mechanical characteristics of SMA element and non-smooth nature of the impacts, five different modes of operation can be distinguished for this system. The undertaken numerical investigation suggests that the system can exhibit complex dynamic responses which if appropriately controlled can be used for vibration reduction. For this reason alone a comparison with an equivalent elastic oscillator was made. It was found out that low amplitude regimes are not affected by the presence of SMA element. On contrary, for the large amplitude responses a significant vibration reduction was achieved due to the phase transformations.
TL;DR: It was found that the interacting crack faces, the crack length and the mutual position of cracks influence the critical strain in the composite, and the complex fracture mechanics problem is solved using the finite-element analysis.
Abstract: The non-classical problem of fracture mechanics of composites compressed along the layers with interfacial cracks is analysed. The statement of the problem is based on the model of piecewise homogeneous medium, the most accurate within the framework of the mechanics of deformable bodies as applied to composites. The condition of plane strain state is examined. The layers are modelled by a transversally isotropic material (a matrix reinforced by continuous parallel fibres). The frictionless Hertzian contact of the crack faces is considered. The complex fracture mechanics problem is solved using the finite-element analysis. The shear mode of stability loss is studied. The results are obtained for the typical dispositions of cracks. It was found that the interacting crack faces, the crack length and the mutual position of cracks influence the critical strain in the composite.
TL;DR: For any choice of a monomial order on the parameters of type Bn, the Specht modules are naturally isomorphic to the Kazhdan-lusztig cell modules as discussed by the authors.
TL;DR: Evaluated educational resources produced by NES to prepare the frontline staff in relation to the Mental Health (Care and Treatment) (Scotland) Act 2003 were effective in assisting professionals in implementing the complex and progressive requirements of the new Mental Health Act.
Abstract: The Mental Health (Care and Treatment) (Scotland) Act 2003 was developed with the participation of patients and carers. This Act is fundamentally different from all previous versions of the Mental Health Acts in the UK because it is based on Millan's 10 principles. Its objective is to ensure that people with mental disorder receive effective care and treatment. It is crucial that all staff who deal with persons with mental disorder are familiar with the Act and incorporate it into practice. This depends on the effectiveness of educational resources in supporting staff to develop their practice. The project presented here was commissioned by the National Health Service Education for Scotland (NES) to evaluate the accessibility and use of the educational resources produced for all frontline staff in Scotland. The aim was to evaluate the educational resources produced by NES to prepare the frontline staff in relation to the Mental Health (Care and Treatment) (Scotland) Act 2003. Evaluation was conducted through a questionnaire survey, focus groups and individual interviews. The NES educational resource was effective in assisting professionals in implementing the complex and progressive requirements of the new Mental Health Act. The three formats reached a wide audience, and are an effective model for future initiatives.
TL;DR: In this paper, the authors investigated crack interaction in transversely isotropic materials compressed in a static manner along inter-laminar defects, and they found that the fiber volume fraction, the crack length and the mutual position of cracks influence the critical strain of the composite.
TL;DR: This article argued that Smith's sociologising of religion, as revolutionary as it was, stops short, where his sociology ends, his theology begins, and that Smith was truly a pioneering sociologist of religion but of primitive and ancient religion only.
01 Oct 2008
TL;DR: The analytical result predicts that, in order to obtain bone reinforcement, the frequency and amplitude of vibration should not exceed specified levels, and low-frequency vibration does not stimulate the bone sufficiently to cause significant remodelling.
Abstract: Orthopaedic rehabilitation of osteoporosis by muscle vibration exercise is investigated theoretically using Wolff's theory of strain-induced bone ‘remodelling’. The remodelling equation for finite amplitude vibration to be transmitted to the bone via muscle corresponds to a slowly time-varying non-linear dynamic system. This slowly time-varying system is governed by a Riccatti equation with rapidly varying coefficients that oscillate with the frequency of the applied vibration. An averaging technique is used to determine the effective force transmitted to the bone. This force is expressed in terms of the stiffness and damping parameters of the connected muscle. The analytical result predicts that, in order to obtain bone reinforcement, the frequency and amplitude of vibration should not exceed specified levels. Furthermore, low-frequency vibration does not stimulate the bone sufficiently to cause significant remodelling. The theoretical model herein confirms the clinical recommendations regarding vibratio...
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TL;DR: In this paper, it was shown that for any stable module category of finite-dimensional stable modules, the center of the stable module has infinite dimension in each odd degree, and if p = 2, also in each even degree.
Abstract: We show that for any finite $p$-group $P$ of rank at least 2 and any algebraically closed field $k$ of characteristic $p$ the graded center $Z^*(\modbar(kP))$ of the stable module category of finite-dimensional $kP$-modules has infinite dimension in each odd degree, and if $p=2$ also in each even degree. In particular, this provides examples of symmetric algebras $A$ for which $Z^0(\modbar(A))$ is not finite-dimensional, answering a question raised in [10]
01 Feb 2008
TL;DR: This oscillator behaves both smooth and discontinuous system depending on the value of the smoothness parameter, and new dynamic behaviour is presented for the transitions from the smooth to discontinuous regime.
Abstract: We propose a new archetypal oscillator for smooth and discontinuous systems (SD oscillator). This oscillator behaves both smooth and discontinuous system depending on the value of the smoothness parameter. New dynamic behaviour is presented for the transitions from the smooth to discontinuous regime.
TL;DR: Two important results concerning the invariance of both PS and the MIR are demonstrated and it is shown that for proper time transformations the timing between the cycles of the coupled oscillators can be largely improved.
Abstract: We investigate the effect of general time transformations on the phase synchronization (PS) phenomenon and the mutual information rate (MIR) between pairs of nodes in dynamical networks We demonstrate two important results concerning the invariance of both PS and the MIR Under time transformations PS can neither be introduced nor destroyed and the MIR cannot be raised from zero On the other hand, for proper time transformations the timing between the cycles of the coupled oscillators can be largely improved Finally, we discuss the relevance of our findings for communication in dynamical networks
TL;DR: A model and a computer program are developed to investigate the possibility of making these two laser effects interact constructively to refine the resolution and show substantial improvement in quality of the patterns compared to that achieved by using either effect alone.