pinecone/core-2020-05-10-deduplication huggingface dataset:
Synthesis, Crystal Structure and Magnetic Properties of the Linear-Chain
  Cobalt Oxide Sr5Pb3CoO12

The novel spin-chain cobalt oxide Sr5Pb3CoO12 [P-62m, a = 10.1093(2) A and c
= 3.562 51(9) A at 295 K] is reported. Polycrystalline sample of the compound
was studied by neutron diffraction (at 6 and 295 K) and magnetic susceptibility
measurements (5 to 390 K). The cobalt oxide was found to be analogous to the
copper oxide Sr5Pb3CoO12, which is comprised of magnetic-linear chains at
inter-chain distance of 10 A. Although the cobalt oxide chains (mu_eff of 3.64
mu_B per Co) are substantially antiferromagnetic (theta_W = -38.8 K), neither
low-dimensional magnetism nor long-range ordering has been found; a
local-structure disorder in the chains might impact on the magnetism. This
compound is highly electrically insulating.Comment: To be published in J. Solid State Che
Vibration characteristics of a suspension footbridge

Author's manuscript version. The final published version is available via doi:10.1006/jsvi.1996.0789. Copyright © 1997 Academic Press. All rights reserved.A suspension footbridge located in a tourist attraction in Singapore has a suspended span of 35 m and was designed for static pedestrian and wind loads. In common with other bridges of this type, it is a light, efficient structure and has a lively dynamic performance. Distributed parameter and finite element models were used to understand the vertical plane behaviour of the bridge and a prototype dynamic test using impact excitation was conducted to check the models and investigate the dynamic response. The first two vertical vibration modes were found to occur at the same frequency, 2 Hz, as the average pedestrian footfall. Response to pedestrians was simulated using linear and non-linear models of a moving excitation source. © 1997 Academic Press Limited
Remote vibration measurements: compensation of waveform distortion due to whole body translations

This article was published in the Journal of Sound and Vibration [Elsevier (© Academic Press)] and the definitive version is available at: http://dx.doi.org/10.1006/jsvi.1998.1529Remote vibration measurements using the laser Doppler technique are a practical and increasingly popular alternative to the use of contacting transducers. This study concerns aspects of non-contact measurements that result when the vibrating target additionally undergoes larger scale whole body translation. The characteristics of a single remote measurement of steady state vibration on a body undergoing whole body translation are investigated in both the time and frequency domains, where waveform distortion and whole body target displacement induced harmonics are observed. A technique which compensates for the relative whole body displacement between the target and a remote transducer is introduced, in which two simultaneous remote measurements are combined to derive a closer estimate of the measurement which would be made by a contacting transducer attached to the target surface. A substantial improvement in the data quality obtainable from a single remote measurement is demonstrated using a numerical simulation and in experimental data captured remotely from a golf club head during and immediately following an impact with a golf ball. Remote measurements are particularly suited to analysis of impacting bodies and the displacement compensation technique is thus developed in this paper to investigate transient pulse propagation effects. The improvement in data quality obtained is demonstrated using data pertaining to the deformation of a golf ball during an impact in which the whole ball accelerates forwards rapidly
Dynamics of multi-span continuous straight bridges subject to multi-degrees of freedom moving vehicle excitation

The paper presents an analytical approach to the problem of vehicle-bridge dynamic interaction. Starting from early studies based on a simply supported beam interacting with a lumped mass moving at constant speed, in recent years researchers have improved the models of both the bridge and the vehicle. On this basis, the bridge is modelled here as a multi-span continuous isotropic plate; its response to external loads is defined by applying the mode superposition principle and takes into account both flexural and torsional mode shapes, the latter being usually neglected in the literature. The plate is considered proportionally damped and its modes are computed by means of the Rayleigh-Ritz method. The scheme adopted for the vehicle consists of a seven degrees-of-freedom system moving at constant speed over the isotropic rough bridge surface. The numerical investigation, based on these analytical models, refers to a three-span bridge and includes the importance of torsional mode shapes, of road surface irregularities and of vehicle speed
Torsional and bending vibration measurement on rotors using laser technology

This article was accepted for publication in the Journal of Sound and Vibration [Elsevier © Academic Press]. The definitive version is available at: http://dx.doi.org/10.1006/jsvi.1999.2253Based on the principles of laser Doppler velocimetry, the laser torsional vibrometer (LTV) was developed for non-contact measurement of torsional oscillation of rotating shafts, offering significant advantages over conventional techniques. This paper describes comprehensive theory to account for the sensitivity of the LTV's measurements to shaft motion in all degrees of freedom. The optical geometry of the LTV offers inherent immunity to translational motion of the target shaft, either axial or radial. However, its measurements are sensitive to angular lateral vibration of the shaft. The significance of this sensitivity is compared with the instrument noise floor and typical torsional and lateral vibration levels. Optimum alignments of the instrument are then specified to ensure effective immunity to all lateral motion in typical applications. To overcome this problem more reliably, a new technique is proposed permitting unambiguous measurement of pure torsional vibration in situations where use of a single LTV demonstrates unacceptable sensitivity to angular lateral vibrations. Practical application of this technology is demonstrated with torsional vibration measurements from a diesel engine crankshaft. Simultaneously, previously unattained measurements of shaft bending vibration measurements are made. The first bending mode of the crankshaft was identified and its vibration amplitude and damping estimated. This application of laser vibrometry for non-contact measurements of shaft vibration represents a further step forward in the use of this technology for machinery diagnostics
Hybrid finite element models for piezoelectric materials

In this paper, hybrid variational principles are employed for piezoelectric finite element formulation. Starting from eight-node hexahedral elements with displacement and electric potential as the nodal d.o.f.s, hybrid models with assumed stress and electric displacement are devised. The assumed stress and electric displacement are chosen to be contravariant with the minimal 18 and seven modes respectively. The pertinent coefficients can be condensed at the element level and do not enter the system equation. A number of benchmark tests are exercised. The predicted results indicate that the assumed stress and electric displacements are effective in improving the element accuracy. © 1999 Academic Press.postprin
Vibration of a flexible pipe conveying viscous pulsating fluid flow

The non-linear equations of motion of a flexible pipe conveying unsteadily flowing fluid are derived from the continuity and momentum equations of unsteady flow. These partial di!erential equations are fully coupled through equilibrium of contact forces, the normal compatibility of velocity at the fluid} pipe interfaces, and the conservation of mass and momentum of the transient fluid. Poisson coupling between the pipe wall and fluid is also incorporated in the model. A combination of the finite difference method and the method of characteristics is employed to extract displacements, hydrodynamic pressure and flow velocities from the equations. A numerical example of a pipeline conveying fluid with a pulsating flow is given and discussed
Modelling smart structures with segmented piezoelectric sensors and actuators

In this paper, a number of finite element models have been developed for comprehensive modelling of smart structures with segmented piezoelectric sensing and actuating patches. These include an eight-node solid-shell element for modelling homogeneous and laminated host structures as well as an eight-node solid-shell and a four-node piezoelectric membrane elements for modelling surface bonded piezoelectric sensing and actuating patches. To resolve the locking problems in these elements and improve their accuracy, assumed natural strain and hybrid stress formulations are employed. Furthermore, piezoelectric patches are often coated with metallization. The concept of electric nodes is introduced that can eliminate the burden of constraining the equality of the electric potential for physical nodes lying on the same metallization. A number of problems are studied by the developed finite element models and comparisons with other ad hoc element models are presented.postprin
Laser vibrometers and contacting transducers, target rotation and six degree-of-freedom vibration: what do we really measure?

This article was published in the Journal of Sound and Vibration [Elsevier © Academic Press] and the definitive version is available at: http://dx.doi.org/10.1006/jsvi.2000.3053This paper presents a comprehensive analysis of the velocity sensed by a single laser vibrometer beam incident in an arbitrary direction on a target that is of substantial interest in engineering - a rotating shaft requiring three translational and three rotational co-ordinates to describe its vibratory motion fully. Six separate "vibration sets", each a combination of motion parameters, appear in the full expression for vibration velocity sensitivity and it is shown not to be possible to resolve individual motion components within each set by arrangement, or even manipulation, of laser beams. To place this non-contact transducer velocity sensitivity model in its proper context, the velocity sensitivity of a contacting transducer under identical conditions is also derived and comparison is made between non-contacting and contacting transducer performance. Specific applications of the laser vibrometer theory to radial and axial vibration measurements are set out and it is shown how estimation of radial vibration components is only possible by post-processing, The theory is easily extended to include measurements made with multiple beams, underlining the model's versatility in enabling determination of the vibration component sensitivity of a measurement with any beam orientation or combination of beam orientations. This will prove beneficial in devising further optical configurations for the measurement of torsional, pitch and yaw vibrations
Rotational vibration measurements using laser doppler vibrometry: comprehensive theory and practical application

This article was published in the Journal of Sound and Vibration [Elsevier © Academic Press] and the definitive version is available at: http://dx.doi.org/10.1006/jsvi.2000.3134This paper builds on a previous study of the velocity sensed by a single laser vibrometer beam incident on a target in an arbitrary direction to predict the velocity sensed by multiple laser beams with arbitrary orientations. The usefulness of parallel beam arrangements is demonstrated and a concise new theory for the difference velocity sensitivity for two parallel beams is presented. Parallel beam arrangements for Virtually unambiguous measurement of torsional vibration are presented along with arrangements that allow measurement of the pitch and yaw vibration to be derived. Resolution of individual pitch and yaw motions is shown not to be possible by any geometrical arrangement of the beams but a post-processing technique that enables the genuine pitch and yaw vibrations to be estimated from the measurements of the pitch and yaw vibration sets is demonstrated and validated experimentally in the laboratory. Measurements of pitch and yaw vibration are, for the first time, obtained from the crank-shaft of a running diesel engine, enabling identification of the first natural frequency of the crank-shaft in bending
Simplified techniques for predicting the transmission loss of a circular dissipative silencer

A closed-form analytical solution for the transmission loss of a dissipative silencer with a circular cross-section is described.  The silencer contains a bulk reacting acoustic absorbent which is separated from a mean gas flow by a perforated screen.  Theoretical predictions of the silencer transmission loss for three different dissipative silencers are compared both with experimental data and with another more complex modelling technique.  Good agreement is noted between the analytical theory and experimental data in the low-to-medium frequency range.  Below a defined upper frequency limit the analytical technique is also shown to provide good agreement with the finite element method.  In addition it is observed that, even for relatively high open area porosities, the perforate screen has a significant effect on dissipative silencer performance
Sound transmission through a rib-stiffened plate : comparisons of a light fluid approximation with experimental results

International audienceInterest in stiffened plate constructions has been widespread recently in aerospace, marine and engineering structures : their vibratory response can be greatly modified by small weight added to the hull. Semi-analytical and finite element modellings are mostly based on a weak (energetic) formulation of the in vacuo problem. First, the analysis has been simplified by applying the so-called orthotropic equivalent plate theory only valid when the mechanical wavelengths are greater than the stiffeners spacing~; a more accurate and robust method is the discrete model in which the system is divided into subelements~: the stiffeners are therefore considered as beams exerting efforts on the plate. Moreover, the vibro-acoustic response of the system fluid/structure is approximated under the assumption that the fluid-loading is a small perturbation with respect to the in vacuo problem since the surrounding fluid is a gas. This paper applies this approximation to the case of a baffled plate stiffened by ribs
Surface Quality of a Work Material Influence on Vibrations in a Cutting
  Process

The problem of stability in the machining processes is an important task. It
is strictly connected with the final quality of a product. In this paper we
consider vibrations of a tool-workpiece system in a straight turning process
induced by random disturbances and their effect on a product surface. Basing on
experimentally obtained system parameters we have done the simulations using
one degree of freedom model. The noise has been introduced to the model by the
Langevin equation. We have also analyzed the product surface shape and its
dependence on the level of noise.Comment: 12 pages, PDF of figures can be obtained from
  http://archimedes.pol.lublin.pl/~raf/graf/fpic.pd
Identification of multiple faults in rotor systems

Many papers are available in literature about the identification of faults in rotor systems. However they generally deal with a fault only, usually an unbalance. Instead, in real machines, the case of multiple faults is quite common: the simultaneous presence of a bow (due to several different causes) and an unbalance or a coupling misalignment occurs often in rotor systems. In this paper a model based identification method for multiple faults is presented. The method requires the definition of the models of the elements that compose the system, i.e. the rotor, the bearings and the foundation, as well as  the models of the faults, which can be represented by harmonic components of equivalent force or moment systems. The identification of multiple faults is made by a least square fitting approach in the frequency domain, by means of the minimization of a multidimensional residual between the vibrations in some measuring planes on the machine and the calculated vibrations due to the acting faults. Some numerical applications are reported for two simultaneous faults and some experimental results obtained on a test rig are used to validate the identification procedure. Accuracy and limits of the proposed procedure has been evaluated
Improvement of a tail-plane strucural model using vibration test data.

To achieve the best structural model improvement using vibration test data, a
major effort has been made to identify poor modelling regions as a guideline for
subsequent model updating. The method presented and used in this paper is the
energy error estimation method. In the method the difference between analytical
and test data based energies at element scale is estimated to indicate any poor
structural mass and stiffness modelling. As a result, poor modelling regions can
be distinguished from those modelled correctly and the improvement of the
original structural model can be carried out effectively and accurately. To
demonstrate the application of this method, a full-scale tail-plane structure
has been studied by using simulated "test" modes as a simulated case and using
measured modes as a practical case. In both cases poor modelling regions of the
original structural model have been accurately located. Subsequently, a
significant improvement of the structural model with a reduction of average
frequency error from original 2·2% down to 0·1% for the simulated case and from
4·6 to 1·8% for the practical case has been achi
Selection, Mutations and Codon Usage in Bacterial Model

We present a statistical model of bacterial evolution based on the coupling
between codon usage and tRNA abundance. Such a model interprets this aspect of
the evolutionary process as a balance between the codon homogenization effect
due to mutation process and the improvement of the translation phase due to
natural selection. We develop a thermodynamical description of the asymptotic
state of the model. The analysis of naturally occurring sequences shows that
the effect of natural selection on codon bias not only affects genes whose
products are largely required at maximal growth rate conditions but also gene
products that undergo rapid transient increases.Comment: 15 pages, 3 figure
A mechanochemical model for adult dermal wound contraction: On the permanence of the contracted tissue displacement profile

The healing of adult mammalian skin wounds involves a complex sequence of spatially and temporally coordinated processes. Wound contraction, by reducing the size of the injury, is an intrinsic component of full-thickness excisional dermal wound healing. The underlying biomechanics of wound contraction, however, are not fully understood, and little is known about the pathogenesis of severe medical conditions known as fibrocontractive diseases. The aim of this work is to investigate a deterministic mathematical model in order to obtain insight into the mechanistic relationships between wound contraction and associated normal and pathological healing processes. The model describes the essential roles of fibroblast and myofibroblast cells, a chemical growth factor and the extracellular matrix which includes type I collagen. The model results are qualitatively consistent with the biology of fibroplasia and wound contraction. It is shown that contracted state evolves during a (long) transient phase of healing known as proliferation, while collagen kinetics are fundamental to the considerably longer ‘remodeling' phase. Some quantitative results, notably on the evolution of wound contraction, compare favourably with experimental data. Application of the model to adult human dermal wound healingin vitro, with a greater understanding of the underlying biological mechanisms involved, may suggest strategies for controlling contraction and fibrocontractive diseases
On a model mechanism for the spatial patterning of teeth primordia in the Alligator

We propose a model mechanism for the initiation and spatial positioning of teeth primordia in the alligator,Alligator mississippiensis. Detailed embryological studies by Westergaard & Ferguson (1986, 1987, 1990) show that jaw growth plays a crucial role in the developmental patterning of the tooth initiation process. Based on biological data we develop a reaction-diffusion mechanism, which crucially includes domain growth. The model can reproduce the spatial pattern development of the first seven teeth primordia in the lower half jaw ofA. mississippiensis. The results for the precise spatio-temporal sequence compare well with detailed developmental experiments
Pattern formation by lateral inhibition with feedback: a mathematical model of Delta-Notch intercellular signalling

In many developing tissues, adjacent cells diverge in character so as to create a fine-grained pattern of cells in contrasting states of differentiation. It has been proposed that such patterns can be generated through lateral inhibition—a type cells–cell interaction whereby a cell that adopts a particular fate inhibits its immediate neighbours from doing likewise. Lateral inhibition is well documented in flies, worms and vertebrates. In all of these organisms, the transmembrane proteins Notch and Delta (or their homologues) have been identified as mediators of the interaction—Notch as receptor, Delta as its ligand on adjacent cells. However, it is not clear under precisely what conditions the Delta-Notch mechanism of lateral inhibition can generate the observed types of pattern, or indeed whether this mechanism is capable of generating such patterns by itself. Here we construct and analyse a simple and general mathematical model of such contact-mediated lateral inhibition. In accordance with experimental data, the model postulates that receipt of inhibition (i.e. activation of Notch) diminishes the ability to deliver inhibition (i.e. to produce active Delta). This gives rise to a feedback loop that can amplify differences between adjacent cells. We investigate the pattern-forming potential and temporal behavior of this model both analytically and through numerical simulation. Inhomogeneities are self-amplifying and develop without need of any other machinery, provided the feedback is sufficiently strong. For a wide range of initial and boundary conditions, the model generates fine-grained patterns similar to those observed in living systems
Patch Dynamics and Metapopulation Theory: The Case of Successional Species

We present a mathematical framework that combines extinctionâ€“colonization dynamics with the dynamics of patch succession. We draw an analogy between the epidemiological categorization of individuals (infected, susceptible, latent and resistant) and the patch structure of a spatially heterogeneous landscape (occupiedâ€“suitable, emptyâ€“suitable, occupiedâ€“unsuitable and emptyâ€“unsuitable). This approach allows one to consider life-history attributes that influence persistence in patchy environments (e.g., longevity, colonization ability) in concert with extrinsic processes (e.g., disturbances, succession) that lead to spatial heterogeneity in patch suitability. It also allows the incorporation of seed banks and other dormant life forms, thus broadening patch occupancy dynamics to include sink habitats. We use the model to investigate how equilibrium patch occupancy is influenced by four critical parameters: colonization rate, extinction rate, disturbance frequency and the rate of habitat succession. This analysis leads to general predictions about how the temporal scaling of patch succession and extinctionâ€“colonization dynamics influences long-term persistence. We apply the model to herbaceous, early-successional species that inhabit open patches created by periodic disturbances. We predict the minimum disturbance frequency required for viable management of such species in the Florida scrub ecosystem