Dislocation Phenomena Research Articles

Elastic and inelastic systems under near-fault seismic shaking: acceleration records versus optimally-fitted wavelets

Four idealised dynamic systems, which are used as analogues in earthquake and geotechnical engineering, are studied: an elastic single-degree-of-freedom (sdof) oscillator; an elastic-perfectly-plastic sdof oscillator; a rigid block resting in simple frictional contact on a horizontal base; and a rigid block resting on a sloping plane. They are subjected to sev- eral near-fault-recorded ground motions bearing the effects of 'forward-rupture directivity' and fault surface dislocation ('fling-step') phenomena—long-period acceleration pulses and largevelocityordisplacementsteps.Twotypesofidealizedwavelets(theMavroeidis&Papa- georgiou and the Ricker wavelets) are optimally-fitted to each record, applying the match- ing procedure presented by Vassiliou and Makris (Bull Seismol Soc Am 101(2):596-618, 2011). Extensive comparisons between the accelerogram response and the corresponding- fitted wavelets response show if and when the destructive pulse-like part of the records is indeed their most deleterious component, and if and when this destructiveness can be cap- tured with the particular fitted wavelets. For the two purely inelastic systems, in particular, the comparison elucidates the role of the contained pulses in the size of sliding displace- ments. The results reveal that while the response of elastic and elasto-plastic sdof systems to the wavelets is usually reasonably similar with the response to the actual records, this is not usually the case for the two purely inelastic (sliding) systems. The unpredictable con- sequences of seismic shaking on such systems, even if the shaking intensity and frequency content were precisely known, is best demonstrated with the sensitivity of the size of sliding displacementtothepolarity(+or −),thesequenceandnumberofcycles,andeventhedetails of the excitation.

Numerical simulation on slabs dislocation of Zipingpu concrete faced rockfill dam during the Wenchuan earthquake based on a generalized plasticity model.

After the Wenchuan earthquake in 2008, the Zipingpu concrete faced rockfill dam (CFRD) was found slabs dislocation between different stages slabs and the maximum value reached 17 cm. This is a new damage pattern and did not occur in previous seismic damage investigation. Slabs dislocation will affect the seepage control system of the CFRD gravely and even the safety of the dam. Therefore, investigations of the slabs dislocation's mechanism and development might be meaningful to the engineering design of the CFRD. In this study, based on the previous studies by the authors, the slabs dislocation phenomenon of the Zipingpu CFRD was investigated. The procedure and constitutive model of materials used for finite element analysis are consistent. The water elevation, the angel, and the strength of the construction joints were among major variables of investigation. The results indicated that the finite element procedure based on a modified generalized plasticity model and a perfect elastoplastic interface model can be used to evaluate the dislocation damage of face slabs of concrete faced rockfill dam during earthquake. The effects of the water elevation, the angel, and the strength of the construction joints are issues of major design concern under seismic loading.

Evidence for a spatial bias in the perception of sequences of brief tones

Listeners are unable to report the physical order of particular sequences of brief tones. This phenomenon of temporal dislocation depends on tone durations and frequencies. The current study empirically shows that it also depends on the spatial location of the tones. Dichotically testing a three-tone sequence showed that the central tone tends to be reported as the first or the last element when it is perceived as part of a left-to-right motion. Since the central-tone dislocation does not occur for right-to-left sequences of the same tones, this indicates that there is a spatial bias in the perception of sequences.

A concurrent scheme for passing dislocations from atomistic to continuum domains

This paper presents a concurrent atomistic–continuum (CAC) methodology for three-dimensional dynamic simulation of dislocation nucleation, migration and interaction. The method is based on a new continuum field formulation of balance laws with relevant atomistic information (the arrangements and interactions of atoms) considered. In this work, we show that the new CAC method allows the smooth passage of dislocations through sharp interfaces between the atomistic and the coarse-grained finite element domains without unphysical reflection of dislocations or the need for heuristic rules; meanwhile, complex dislocation phenomena such as dislocation nucleation, dynamic strain bursts associated with nucleation and migration avalanches, formations of Lomer–Cottrell locks, dislocation–rigid boundary interactions, formation of intrinsic and extrinsic stacking faults, deformation twinning, and curved dislocation loops can be reproduced by the CAC method. All of the CAC simulations are directly compared with the corresponding atomic-level molecular dynamics (MD) simulations. The efficiency, accuracy and potential applications of the method are discussed along with necessary additional development of criteria for coarse graining.

Fronting, dislocation, and the syntactic role of discourse-related features

This paper focuses on the syntactic role of the features related to discourse and information structure. It is argued that information-structure notions are encoded in syntax as syntactic features projecting their own phrase structure, and are fundamental in accounting for cross-linguistic variation. The word order alternations and syntactic operations which are strictly dependent on the discourse/informational properties of the sentence, as well as the different grammatical properties characterizing different information-structure categories, can all be related to the syntactic role of discourse-related features, the functional projections with which they are associated, and the type of movement that these features trigger. Under this view, this paper offers an analysis of fronting and dislocation phenomena in Romance, which entails that variation with respect to these processes is correlated to the activation and to the attraction properties of the functional projections encoding information-structure distinctions. Keywords: discourse-related features; information structure; functional projections; topic; informational focus; contrastive focus; Romance; Sicilian

A large laterally displaced osteochondral fragment from dislocated patella: Case report and possible mechanism

Dislocation of the patella is not a common disorder of the knee joint and is seen most frequently in the adolescent population. Osteochondral fractures account for approximately 5-74% of all acute patellar dislocations and are easy to overlook. The mechanism of injury and presentations of fractured fragments were seldom well describe in published studies. The case reported here is that of a 17-year-old baseball player who suffered an acute patellar dislocation with a large osteochondral fragment fracture, where the fragment presented over the lateral supracondylar aspect of the distal femur. Open reduction and fixation with Kirschner wires gave a good result. Osteochondral fracture of patella is usually regarded as a dislocation phenomenon. However, we review and discuss here three injury mechanisms, and suggest the possible mechanisms by which patellar relocation could have caused our patient’s injury and the rare occurrence of a laterally displaced osteochondral fragment over the distal femur.

Norwegian (non-V2) declaratives, resumptive elements, and the Wackernagel position

Most Norwegian declaratives are subject-initial verb second (V2) clauses. This paper discusses declaratives that can be construed as non-V2, two constructions that have traditionally been analyzed as left dislocation phenomena: the (adjunctive)så-construction and the Copy Left Dislocation (CLD) construction, where the ‘copy’ is a weak pronoun. Both constructions share an affinity to root clauses, have particular scope effects, and employ a prosodically light particle between the topicalized phrase and the finite verb in V2 (såand a weak pronoun, respectively). The paper attributes these properties to the fact that the relevant particles are topic markers of a particular kind; they mark A-topics. A-Topics signal a topic-shift in the conversation and are confined to clauses with illocutionary force (Bianchi & Frascarelli 2010). The aforementioned particles are much more frequent in spoken contexts than in written prose, and I propose that this is because they depend on prosody. They are obligatorily light, and they occur in the part of the clause that has traditionally been described as ‘the Wackernagel position’. Wackernagel (1892) proposed that certain prosodically light elements (clitics in particular) tend to occur in the second position in Indo-European languages. Although the resumptive elements of theså-construction and especially of CLDs may not be fully-fledged clitics, like clitics, they appear in the second position of declaratives.

Experimental study on the wake behind tapered circular cylinders

The flow around tapered cylinders can act as basic models for numerous bluff body flows with a spanwise variation of either the body shape or the inflow conditions. The well-known vortex street is influenced by strong three-dimensional effects from the spanwise variation of the shedding frequency, namely oblique vortex shedding and vortex dislocations. Stereo-PIV was chosen to study these phenomena, since it allows analyzing planes with the full three-component, instantaneous velocity fields and local, time-dependent variations in the same setting. Hence, detailed aspects of the vortex dislocation phenomenon are presented. Single vortex dislocation events are presented through the local variation of the three measured velocity components u, v and w. Longer time-series reveal both period and location of these dislocation events, as well as quantity and sizes of the cells of constant shedding velocity in between them. The influence of the Reynolds number and the cylinder aspect ratio on the vortex cells could be shown. The analysis of the vortex shedding behavior shows good agreement with previously published results. At the same time, the applied PIV technique provides more spatial information than point-based measurements and offers insight into a Reynolds number range that is currently out of reach of Direct Numerical Simulations.

Application Design of CAN Bus (CANOpen) for Rotary Screen Printing Machine

The background of this paper is Rotary Screen Printing Machine(RSPM),and the paper need to resolve the printing flower dislocation phenomenon caused by synchronization between each motor, and by the synchronization between rotary screen motor and the conduction band. The paper presented overall scheme, and analyzed, designed and realized synchronous control arithmetic design based on system hardware platform. Through some related experimental results proved that the distributed system based on CAN bus(CANOpen protocol) worked stably, each motor transmitted independently and could run synchronously , and the results verified the correctness and feasibility of distributed structure scheme used for RSPM system.

MR evaluation of synovial injury in shoulder trauma

The purpose of this study was to determine magnetic resonance imaging (MRI) findings relevant to synovial injury of the shoulder in patients with and without acute shoulder trauma. Three hundred and nine consecutive shoulder MRI studies (185-male, 124-female, 50 ± 15 years old) were retrospectively evaluated for findings suggestive of synovial injury including rupture and/or diverticulum of the joint capsule, bursa, and biceps tendon sheath (BTS), ganglion/synovial cyst, geyser phenomenon, and sequel of previous shoulder dislocation (Hill-Sachs deformity). Patients with one or more of these findings were included in the MR-positive group, whereas the remaining subjects were used as MR negatives. Based on their medical records, patients were also divided into trauma and non-trauma groups, and statistical analysis was performed to evaluate the association between the aforementioned MRI findings and history of shoulder trauma. Fifty-six patients were included in the MR-positive group and 253 in the MR-negative group. In MR-positive group, the incidence of capsular rupture (CR) and subacromial/subdeltoid (SASD) bursal rupture was higher in trauma patients, whereas the incidence of BTS diverticulum and ganglion cyst was higher in subjects without trauma. Significant association was found between the history of acute trauma and CR, SASD bursal rupture, BTS rupture, and Hill-Sachs deformity. In shoulder MR examination, presence of CR and/or SASD bursal rupture is strongly suggestive of acute shoulder trauma. In addition, BTS rupture and Hill-Sachs deformity are more prevalent in patients with acute shoulder trauma. The presence of these features should alert MRI readers to assess for additional trauma-related internal derangements, if a respective history has not been provided.

Coarse-grained atomistic simulation of dislocations

This paper presents a new methodology for coarse-grained atomistic simulation of dislocation dynamics. The methodology combines an atomistic formulation of balance equations and a modified finite element method employing rhombohedral-shaped 3D solid elements suitable for fcc crystals. With significantly less degrees of freedom than that of a fully atomistic model and without additional constitutive rules to govern dislocation activities, this new coarse-graining (CG) method is shown to be able to reproduce key phenomena of dislocation dynamics for fcc crystals, including dislocation nucleation and migration, formation of stacking faults and Lomer–Cottrell locks, and splitting of stacking faults, all comparable with fully resolved molecular dynamics simulations. Using a uniform coarse mesh, the CG method is then applied to simulate an initially dislocation-free submicron-sized thin Cu sheet. The results show that the CG simulation has captured the nucleation and migration of large number of dislocations, formation of multiple stacking fault ribbons, and the occurrence of complex dislocation phenomena such as dislocation annihilation, cutting, and passing through the stacking faults. The distinctions of this method from existing coarse-graining or multiscale methods and its potential applications and limitations are also discussed.

Intensity Distribution and Phase Vortices of Speckle Fields Generated by Multi-Aperture Random Scattering Screens

The intensity distribution and phase vortices of the speckle fields generated by multi-aperture random scattering screens are simulated, and it is found that the vortices exhibit layer-like structures and the dislocation phenomena occur in the local phase patterns produced by the two-pinhole aperture, whose phase distributions appear as striped structures. For three- or four-pinhole aperture, there are many circular bright spots appearing in the speckle grains, and there is one vortex between the neighboring circular bright spots. The positive and negative phase vortex lattices appear in the phase distributions, and the regions circled by the isothetic phase lines form irregular quadrilaterals or hexagons. Moreover, the relative positions of the vortices or bright spots can be adjusted by changing those of the pinhole apertures.

The Anelasticity of the Mantle*

The attenuation of seismic waves provides the most direct data regarding the non-elastic properties of the Earth. Recent experimental results from body waves, surface waves and free oscillations provide estimates of the anelasticity in various regions of the Earth. Results to date show that the upper mantle is more attenuating than the lower mantle, the maximum attenuation is in the vicinity of the low-velocity zone, a rapid increase in attenuation occurs in the vicinity of the C-region of the mantle and compressional waves are less attenuated than shear waves. A frequency dependence of Q has not yet been discovered. Most laboratory measurements of attenuation have been performed at ultrasonic frequencies on pure specimens of metals, glasses, plastics and ceramics. A general feature of laboratory measurements is an exponential increase of attenuation with temperature on which are superimposed peaks which can be attributed to dislocation or other defect phenomena. Measurements on natural rocks at atmospheric pressure can be attributed to the presence of cracks. The intrinsic attenuation of rocks as a function of temperature and pressure is not known. However, on other materials grain boundary phenomena dominate at high temperature. This can be attributed to increased grain boundary mobility at high temperatures. High pressure would be expected to decrease this mobility. If attenuation in the mantle is due to an activated process it is probably controlled by the diffusion rate of defects at grain boundaries. Estimates of attenuation in the lower mantle then yield an estimate of the activation volume of the defects contributing to the loss. If the lower mantle is assumed homogeneous the estimated activation volume is a small fraction of the presumed molal volume of materials making up the lower mantle. Stress induced migration of small point defects is a possible loss mechanism consistent with the observations.

Inhomogenous Dislocation Nucleation Based on Atom Potential in Hexagonal Noncentrosymmetric Crystal Sheet

By introducing internal degree, the deformation of hexagonal noncentrosymmetric crystal sheet can be described by the revised Cauchy–Born rule based on atomic potential. The instability criterion is deduced to investigate the inhomogeneous dislocation nucleation behavior of the crystal sheet under simple loading. The anisotropic characters of dislocation nucleation under uniaxial tension are studied by using the continuum method associated with the instability criterion. The results show a strong relationship between yield stress and crystal sheet chirality. The results also indicate that the instability criterion has sufficient ability to capture the dislocation nucleation site and expansion. To observe the internal dislocation phenomenon, the prediction of the dislocation nucleation site and expansion domain is illustrated by MD simulations. The developed method is another way to explain the dislocation nucleation phenomenon.

A Study on Control Structure for Slide Screw Stages

A slide screw drive is a kind of old technology. However it is usable and important technology even in high-tech fields such as semiconductor manufacturing. This paper intends to improve the slide screw controllability which has strong non-linearity due to grease characteristics. We measured the grease non-linear viscosity using a special tool. This grease property explains the shot dislocation phenomenon which occurs in slide screw stages particularly. Since we understood the phenomenon, we found one non-linear gain control method which embedded the grease property reversely. It not only fixed the dislocation problem but also enhanced the slid screw stage performance and maintainability.

Toward a Dynamical Interpretation of Hierarchical Linguistic Structure

UC Berkeley Phonology Lab Annual Report (2009) Toward a dynamical interpretation of hierarchical linguistic structure Sam Tilsen 1. Introduction Hierarchy is one of the most important concepts in the scientific understanding of language. From early structuralist approaches of the mid-1800s, through the paradigm shift to generative grammar in the mid-1900s, and onward to the present, connected-object (“branching”) schemas have been used to represent hierarchical constituency relations between linguistic units. Syntactic trees are the most prominent instantiation of such schemas, but similar arboreal schemas have been applied extensively in nearly all domains of linguistic theory. Recently, an alternative conception of hierarchical structure has arisen, which is based upon interactions between waves, or coupled oscillatory systems. This paper presents a synthesis and extension of such approaches, with the aim of advancing a general wave theory of linguistic structure. This wave theory provides a coherent conceptualization of diverse linguistic phenomena, is cognitively plausible, and is a parsimonious theory. Many syntactic and phonological patterns in language can be understood to arise from general principles of wave interaction. Section 1.1 will consider how hierarchy has traditionally been conceptualized and represented in linguistics, and section 1.2 will describe some previous research which leads the way to a wave-based, dynamical systems perspective on linguistic structure. Section 2 will introduce some general principles regarding how hierarchical structure can be conceptualized with dynamical systems, beginning with systems of two waves, then treating systems of three waves, which can be generalized to more complex systems. This is followed in section 3 by several applications of the theory to phonological and syntactic patterns. These include an examination of how segments interact with syllables and how stress interacts with words, as well as a proposal for dynamical modeling of recursive syntactic patterns and syntactic dislocation phenomena. Section 4 concludes with a discussion of the cognitive plausibility of this approach, and delineates some issues to guide further development of the theory. 1.1 Hierarchical Structure In this paper we are interested in a structural notion of hierarchy, in which concepts of ranking, relation, and containment play important roles. In order to organize our

MIKE BAYNHAM AND ANNA DE FINA (eds.), Dislocations/relocations: Narratives of displacement

Mike Baynham and Anna de Fina (eds.), Dislocations/relocations: Narratives of displacement. Manchester, UK & Northampton, MA: St. Jerome, 2005. Pp. 262. Pb. £19.99.Clearly announced in the title, the topic of this collection of essays is the experience of spatial displacement conveyed through narrative by the individuals who undergo it. The authors approach it as a theoretical and methodological problem in narrative studies, as well as an opportunity for reflecting on a social and political phenomenon – the (forced or freely chosen) movement of people – that has come to be seen as central to the experience of modernity (2). The project is very ambitious. It not only seeks to make a conceptual contribution to the already vast and multidisciplinary literature on narrative, but also hopes to address enough instances of discursive practices that involve migrants and minorities around the world to be able to claim that it sheds light on the general phenomenon of displacement. Overall, the book is stronger when it addresses its second objective, and it offers a multi-layered and comprehensive analysis of the phenomenon of dislocation as captured through narrative practices. What contributes to the success of the book are, in addition to the quality of the individual contributions, its rigorous organization in parts that cohere conceptually and thematically, the clear justification of the project offered by the two editors in an excellent introduction, and the concluding remarks by James Collins, which leave the reader with a sense of a consistent intellectual product.

Size‐dependent elastic interaction between a screw dislocation and a circular nano‐hole with surface stress

AbstractThe effect of surface stress on the size‐dependent interaction of a screw dislocation with a circular nano‐hole under remote antiplane shear loads is examined. By using the complex variable method, the analytical expressions of the complex potential in infinite matrix and the image force acting on the screw dislocation are obtained. The associated solutions to the problem of a screw dislocation interacting with a nano‐inhomogeneity are also given. The results show that the influence of the surface stress on the motion of the dislocation near the hole becomes remarkable when the size of the hole is reduced to nanometer scale, leading to that the normalized image force depends on the hole size which differs from the size‐independent classical elastic solution. Our results are helpful in the understanding of the motion mechanism of the dislocation and relevant physical phenomena in nano‐structured materials. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Length Effect on Formation of Metallic Patterns by Nanoimprinting Process – Molecular Dynamics Simulation

The nanoimprinting process between a nickel mold and a gold thin film consisting of 9500 – 11000 atoms was studied using molecular dynamics computational simulation. The nickel mold and the gold thin film were both formed in face central cubical (FCC) single crystal, and the simulation condition was in an isothermal state of 300K. The Morse potential was utilized in order to determine interatomic forces and potentials. During the nanoimprinting process, jump-to-contact, thin-film recovery, slip-line like, dead-metal zone and dislocation phenomena were observed. After finishing nanoimprinting processes, the interactive force curves between the mold pattern and thin film, and those inside the thin film were measured. By varying the pattern width of the mold and incorporating the measured force curves inside the thin film, the length effect on metallic pattern formation can be determined. In addition, through analytical investigation, it can be observed that the thin-film thickness, the pattern width of the mold, and the applied force should be matched up very well in order to obtain good formation of metallic pattern.

Evolution of the statistical properties of dislocation ensembles

X-ray line profile analysis is an efficient non-destructive technique to determine some key statistical properties of dislocation structures developing during plastic deformation. In the first part of the paper recent developments describing the asymptotic behavior of the line profiles are outlined. A new evaluation method is presented to determine the average dislocation density and its spatial variation. The method is demonstrated on measurements obtained on compressed Cu single crystals. After this, it is shown that the relative dislocation density fluctuation exhibits a sharp maximum at the stages II–III transition. A nanoindentation tests indicate that the fluctuations of other quantities behave similarly. The results give new insight into the dislocation phenomena taking place in the stage III deformation regime.