WorldWideScience

Sample records for dislocation climb mechanism

  1. Rate controlling mechanisms during hot deformation of Mg–3Gd–1Zn magnesium alloy: Dislocation glide and climb, dynamic recrystallization, and mechanical twinning

    International Nuclear Information System (INIS)

    Mirzadeh, H.; Roostaei, M.; Parsa, M.H.; Mahmudi, R.

    2015-01-01

    Highlights: • Hot deformation behavior and dynamic recrystallization of GZ31 magnesium alloy. • Deducing the operative deformation mechanisms by constitutive analysis. • Viscous glide as the rate controlling step during hot working of GZ31 alloy. • Characterization of the effect of mechanical twinning on constitutive relations. - Abstract: The flow behavior of the Mg–3Gd–1Zn (GZ31) magnesium alloy during hot working was critically analyzed and dislocation glide in the form of a viscous drag process (viscous glide) was identified as the rate controlling mechanism due to interaction of rare earth Gd atoms with the moving dislocations. Mechanical twinning was shown to significantly affect the level of flow stress at high Zener–Hollomon parameters, i.e. low forming temperatures and high strain rates. Moreover, dynamic recrystallization (DRX) was found to be another responsible phenomenon for deviation of constitutive equations from the theoretical ones, namely the deformation activation energy based on diffusivity and the pre-defined Garofalo’s type hyperbolic sine power, during high-temperature thermomechanical processing of this creep resistant light alloy

  2. Large-Strain Softening of Aluminum in Shear at Elevated Temperature: Influence of Dislocation Climb

    Science.gov (United States)

    Kassner, M. E.; Campbell, C. S.; Ermagan, R.

    2017-09-01

    This communication complements an earlier publication in this journal by the authors describing the basis for large-strain softening in aluminum under pure shear at elevated temperatures. Earlier work by the authors and the materials community only considered changes in the dislocation glide stress with the evolving texture as an explanation for the softening. New analysis finds that changes in the dislocation climb stress with texture development can explain the softening trends.

  3. Dislocation Climb Sources Activated by 1 MeV Electron Irradiation of Copper-Nickel Alloys

    DEFF Research Database (Denmark)

    Barlow, P.; Leffers, Torben

    1977-01-01

    of irradiation temperatures corresponding to the highest source densities is approximately 350°–500°C. The climb sources are not related to any pre-existing dislocations resolved in the microscope. The sources emit three types of loop: ‘rectangular’ loops with a100 Burgers vector and {100} habit plane, normal......Climb sources emitting dislocation loops are observed in Cu-Ni alloys during irradiation with 1 MeV electrons in a high voltage electron microscope. High source densities are found in alloys containing 5, 10 and 20% Ni, but sources are also observed in alloys containing 1 and 2% Ni. The range...... prismatic loops with Burgers vector a/2110, and Frank loops. There is no significant difference between the apparent activation energy for growth of the three types of loops. The source points are suggested to be submicroscopic nickel precipitates-with reference to the existing evidence that...

  4. Effect of Dislocation Mechanisms during Extrusion of Nanostructured Aluminum Powder Alloy

    Science.gov (United States)

    Jorge, A. M.; Peres, M. M.; Kiminami, C. S.; Bolfarini, C.; Botta, W. J.

    2009-12-01

    Nanostructured Al-3.0Fe-0.42Cu-0.37Mn powder alloy was deformed by extrusion over a temperature range of 375 °C to 425 °C, a ram speed range of 1 to 30 mm/s, and an extrusion rate of 10:1. Flow stresses and strain rates were calculated from the experimental ram pressures and speeds. The stress-strain-rate-temperature relationship in the extrusion of the nanostructured alloy was found to be similar to that in hot-worked conventional materials. The extrusion, torsion, compression, and creep data of nanostructured and conventional materials, extending over ten orders of magnitude of strain rate and over two orders of magnitude of stress, were correlated by a hyperbolic-sine constitutive equation, because the power and exponential laws lose linearity at high and low stresses, respectively. The hyperbolic-sine equation is widely used to correlate the hot-working behavior of conventional materials. It was concluded that the hot working of nanostructured powders is a thermally activated process in which the rate-controlling mechanism is the climb of edge dislocations. Microstructural changes in the consolidated alloys as a function of the extrusion conditions were investigated. An analysis was made of the dislocation behavior in very small grains of nanostructured metal by transmission electron microscopy (TEM) and we identified a dislocation structure and the different ways it appears in 40- to 100-nm Al-alloy grains. We also discuss the thermally activated propagation of dislocations and their interactions with shear bands/grain boundaries (SBs/GBs), and dislocation loops. Microstructural features including low-angle GBs, high-angle GBs, and equilibrium GBs and subgrain boundaries were observed. Dislocation structures under a deformation condition were studied to investigate the microstructural evolutions, which revealed some unique microstructural features such as dislocation tangle zones (DTZs) and dense-dislocation walls (DDWs), and the recovery process is

  5. Mechanical Design and Dynamcis of an Autonomous Climbing Robot for Elliptic Half-shell Cleaning

    Directory of Open Access Journals (Sweden)

    Houxiang Zhang

    2008-11-01

    Full Text Available This paper presents an auto-climbing robot for cleaning the elliptic half-shell of National Grand Theatre in China. The robot consists of a climbing mechanism, a moving mechanism, two cleaning brushes and supporting mechanisms. The mechanism and unique aspects are presented in detail. A distributed control system based on CAN bus is designed to meet the requirements of controlling the robot. After that the emphasis for discussion is on the motion realization which includes climbing and cleaning movements. The robot independently climbs and descends in the vertical direction and cleans in the horizontal direction. It takes the circling tracks as supports for climbing up and down between strips and moving horizontally along one strip around the ellipsoid. For system design and control purposes, the dynamic models of the climbing and cleaning processes are given applying of the Lagrange equation. Furthermore the force distribution of the front and rear supporting mechanisms is computed in a way that ensures the safety of the climbing process. In the end, the successful on-site tests confirm the principles described above and the robot's ability.

  6. Mechanical Design and Dynamcis of an Autonomous Climbing Robot for Elliptic Half-shell Cleaning

    Directory of Open Access Journals (Sweden)

    Houxiang Zhang

    2007-12-01

    Full Text Available This paper presents an auto-climbing robot for cleaning the elliptic half-shell of National Grand Theatre in China. The robot consists of a climbing mechanism, a moving mechanism, two cleaning brushes and supporting mechanisms. The mechanism and unique aspects are presented in detail. A distributed control system based on CAN bus is designed to meet the requirements of controlling the robot. After that the emphasis for discussion is on the motion realization which includes climbing and cleaning movements. The robot independently climbs and descends in the vertical direction and cleans in the horizontal direction. It takes the circling tracks as supports for climbing up and down between strips and moving horizontally along one strip around the ellipsoid. For system design and control purposes, the dynamic models of the climbing and cleaning processes are given applying of the Lagrange equation. Furthermore the force distribution of the front and rear supporting mechanisms is computed in a way that ensures the safety of the climbing process. In the end, the successful on-site tests confirm the principles described above and the robot's ability.

  7. Riemann–Cartan Geometry of Nonlinear Dislocation Mechanics

    KAUST Repository

    Yavari, Arash

    2012-03-09

    We present a geometric theory of nonlinear solids with distributed dislocations. In this theory the material manifold-where the body is stress free-is a Weitzenböck manifold, that is, a manifold with a flat affine connection with torsion but vanishing non-metricity. Torsion of the material manifold is identified with the dislocation density tensor of nonlinear dislocation mechanics. Using Cartan\\'s moving frames we construct the material manifold for several examples of bodies with distributed dislocations. We also present non-trivial examples of zero-stress dislocation distributions. More importantly, in this geometric framework we are able to calculate the residual stress fields, assuming that the nonlinear elastic body is incompressible. We derive the governing equations of nonlinear dislocation mechanics covariantly using balance of energy and its covariance. © 2012 Springer-Verlag.

  8. Dislocation

    Science.gov (United States)

    ... forcefully on a body part, such as your hip or shoulder. Heredity. Some people are born with ligaments that are looser and more prone to injury ... accidents. These are the most common cause of hip dislocations, especially for people ... the muscles, ligaments and tendons that reinforce the injured joint Nerve ...

  9. Strengthening mechanisms and dislocation processes in <111> textured nanotwinned copper

    International Nuclear Information System (INIS)

    Zhao, Xing; Lu, Cheng; Tieu, Anh Kiet; Pei, Linqing; Zhang, Liang; Cheng, Kuiyu; Huang, Minghui

    2016-01-01

    We use molecular dynamics simulations to elucidate the deformation mechanisms of <111> textured nanotwinned materials under tensile loading parallel to the twin boundary (TB). Our simulations reveal that the tensile strength of nanotwinned Cu increases monotonically as the twin spacing decreases. The strengthening effect mainly results from TB restricting the transmission of dislocations across the TB. Throughout the simulations the transmissions of dislocations across the TBs dominate the plastic deformation. Both direct and indirect transmissions are identified at atomic level. Direct transmission involves either successive transmission of the leading and trailing partials as in the Fleischer cross-slip model or absorption and desorption of the extended dislocation as in the Friedel-Escaig cross-slip mechanism. In contrast, indirect transmission involves the formation of special superjogs. The persistent slip transfer leaves zigzag slip traces on the cross-sectional view and the inhomogeneous deformation leads to the formation of intersecting slip bands on the plane view.

  10. On the development a pneumatic four-legged mechanism autonomous vertical wall climbing robot

    International Nuclear Information System (INIS)

    Mohamad Shukri Zainal Abidin; Shamsudin H.M. Amin . shukri@suria.fke.utm.my

    1999-01-01

    The paper describes the design of a prototype legged mechanism together with suction mechanism, the mechanical design, on-board controller and an initial performance test. The design is implemented in the form of a pneumatically powered multi-legged robot equipped with suction pads at the sole of the feet for wall climbing purpose. The whole mechanism and suction system is controlled by controller which is housed on-board the robot. The gait of the motion depended on the logic control patterns as dictated by the controller. The robot is equipped with sensors both at the front and rear ends that function as an obstacle avoidance facility. Once objects are detected, signals are sent to the controller to start an evasive action that is to move in the opposite direction. The mechanism has been tested and initial results have shown promising potential for an autonomous mobile. (Author)

  11. Dislocation/hydrogen interaction mechanisms in hydrided nanocrystalline palladium films

    International Nuclear Information System (INIS)

    Amin-Ahmadi, Behnam; Connétable, Damien; Fivel, Marc; Tanguy, Döme; Delmelle, Renaud; Turner, Stuart; Malet, Loic; Godet, Stephane; Pardoen, Thomas; Proost, Joris; Schryvers, Dominique

    2016-01-01

    The nanoscale plasticity mechanisms activated during hydriding cycles in sputtered nanocrystalline Pd films have been investigated ex-situ using advanced transmission electron microscopy techniques. The internal stress developing within the films during hydriding has been monitored in-situ. Results showed that in Pd films hydrided to β-phase, local plasticity was mainly controlled by dislocation activity in spite of the small grain size. Changes of the grain size distribution and the crystallographic texture have not been observed. In contrast, significant microstructural changes were not observed in Pd films hydrided to α-phase. Moreover, the effect of hydrogen loading on the nature and density of dislocations has been investigated using aberration-corrected TEM. Surprisingly, a high density of shear type stacking faults has been observed after dehydriding, indicating a significant effect of hydrogen on the nucleation energy barriers of Shockley partial dislocations. Ab-initio calculations of the effect of hydrogen on the intrinsic stable and unstable stacking fault energies of palladium confirm the experimental observations.

  12. Mechanisms for decoration of dislocations by small dislocation loops under cascade damage conditions

    DEFF Research Database (Denmark)

    Trinkaus, H.; Singh, B.N.; Foreman, A.J.E.

    1997-01-01

    . This effect may arise as a result of either (a) migration and enhanced agglomeration of single SIAs in the form of loops in the strain field of the dislocation or (b) glide and trapping of SIA loops (produced directly in the cascades) in the strain field of the dislocation, In the present paper, both...... of these possibilities are examined. It is shown that the strain field of the dislocation causes a SIA depletion in the compressive as well as in the dilatational region resulting in a reduced rather than enhanced agglomeration of SIAs. (SIA depletion may, however, induce enhanced vacancy agglomeration near dislocations...

  13. Dislocation mobility mechanisms at medium temperatures in very high purity lead (99.9999%)

    International Nuclear Information System (INIS)

    Gallego, I.; No, M.L.; San Juan, J.

    1998-01-01

    The internal friction spectrum of high purity lead (99.9999%) at medium temperatures has been studied. A new peak (P 1 ) has been found at 240 K, which has not been studied up to now. The activation energy of the process associated with P 1 has been determined and its experimental behaviour has also been systematically studied. The comparison between the results and the theoretical predictions of the models of dislocation mobility allows us to attribute the P 1 peak to the sliding of dislocations controlled by the climbing of jogs induced by the diffusion of vacancies along the dislocation line. This conclusion is analogue to that obtained in previous works for the P 1 peak in very high purity aluminium (99.9999%). (Author) 13 refs

  14. 〈Original Papers〉A Design of Stair-climbing Personal Mobility Robot Based on Inverted Pendulum Mechanism

    OpenAIRE

    友國, 伸保

    2012-01-01

    [synopsis] In this paper, an inverted pendulum type personal mobility robot with virtual wheel is described. The robot enables to climb a stairs only with two virtual wheels consist of one rotary link and two wheels which are attached to the both ends of the rotary link. The mechanical dimensions of the rotary link and tire restrict applicable step size. Therefore these mechanical dimensions are delivered by an analysis based on Building Code.

  15. Bilateral Asymmetric Dislocations of Hip Joints: An Unusual Mechanism of Injury

    Directory of Open Access Journals (Sweden)

    Rajesh Kumar Kanojia

    2013-01-01

    Full Text Available Asymmetric bilateral dislocations of the hips are rare injuries. Among the small number of reports in the literature, most have attributed the cause to high-velocity motor crashes. These dislocations are often seen to be associated with fractures of the proximal femur or the acetabulum. We present a case of a 45-year-old man with bilateral asymmetric dislocation of hips which were purely ligamentous in nature, without any fracture. He sustained his injuries due to a fall while getting on a moving bus. It was an unusual mechanism of injury as compared to the other cases of asymmetric hip dislocations reported in published studies. Both hips were reduced under general anaesthesia within three hours of the trauma. Skin traction and non-weight-bearing rehabilitation were continued for six weeks. After 35 months of followup, the patient remains asymptomatic. Early diagnosis and timely reduction of such dislocations under anaesthesia are necessary for prevention of complications.

  16. Deformation induced dislocation boundaries: Alignment and effect on mechanical properties

    DEFF Research Database (Denmark)

    Winther, G.; Juul Jensen, D.

    1997-01-01

    The dislocation boundaries formed during cold-rolling of FCC metals have been reported to have a preferred macroscopic direction with respect to the sample axes. However, boundaries have also been reported to form on crystallographic slip planes. The directions of the boundaries formed...

  17. Effect of dislocations of forest on relaxation of mechanical stresses in irradiated zinc crystals

    International Nuclear Information System (INIS)

    Troitskij, O.A.; Kalymbetov, P.U.; Kusainov, S.G.; Shambulov, N.B.

    1988-01-01

    Effect of forest dislocations on the value of electron-plastic effect (EPE) in zinc crystals during their irradiation by accelerated electron packets is investigated. The following mechanical parameters are determined experimentally: total relaxation of voltages Δσ for 180s; change in reforming voltage Δσpl in single pulses of irradiation on the slope and bottom of relaxation curves. The results obtained testify to the effectiveness of forest dislocations as surmountable obstacles for the dislocations shiding in the basis plane

  18. Dislocation mechanism of acoustic anomalies in superconducting niobium

    International Nuclear Information System (INIS)

    Pal-Val, P.P.; Natsik, V.D.; Pal-Val, L.N.; Kustova, T.V.

    1996-01-01

    The temperature and magnetic field dependences of low-frequency ultrasound absorption in niobium single crystals of different purity have been investigated in the temperature range 2 to 12 K. It is shown for the first time that the unusual sound absorption behaviour, which was previously observed in niobium at the transition from the superconducting (s-) to the normal (n-) state (via the mixed (m-) state), can be explained by the presence of an acoustic relaxation peak at these temperatures and by an anomalous shift of this peak during the s-m-n transition. A theory of the relaxation based on the model of resonant interaction of sound with dislocation kink chains, generated in screw dislocations under the action of thermoelastic stresses during rapid sample cooling, is suggested. (orig.)

  19. Dislocation nucleation facilitated by atomic segregation

    Science.gov (United States)

    Zou, Lianfeng; Yang, Chaoming; Lei, Yinkai; Zakharov, Dmitri; Wiezorek, Jörg M. K.; Su, Dong; Yin, Qiyue; Li, Jonathan; Liu, Zhenyu; Stach, Eric A.; Yang, Judith C.; Qi, Liang; Wang, Guofeng; Zhou, Guangwen

    2018-01-01

    Surface segregation--the enrichment of one element at the surface, relative to the bulk--is ubiquitous to multi-component materials. Using the example of a Cu-Au solid solution, we demonstrate that compositional variations induced by surface segregation are accompanied by misfit strain and the formation of dislocations in the subsurface region via a surface diffusion and trapping process. The resulting chemically ordered surface regions acts as an effective barrier that inhibits subsequent dislocation annihilation at free surfaces. Using dynamic, atomic-scale resolution electron microscopy observations and theory modelling, we show that the dislocations are highly active, and we delineate the specific atomic-scale mechanisms associated with their nucleation, glide, climb, and annihilation at elevated temperatures. These observations provide mechanistic detail of how dislocations nucleate and migrate at heterointerfaces in dissimilar-material systems.

  20. Design and Optimal Research of a Non-Contact Adjustable Magnetic Adhesion Mechanism for a Wall-Climbing Welding Robot

    Directory of Open Access Journals (Sweden)

    Minghui Wu

    2013-01-01

    Full Text Available Wall-climbing welding robots (WCWRs can replace workers in manufacturing and maintaining large unstructured equipment, such as ships. The adhesion mechanism is the key component of WCWRs. As it is directly related to the robot's ability in relation to adsorbing, moving flexibly and obstacle-passing. In this paper, a novel non-contact adjustably magnetic adhesion mechanism is proposed. The magnet suckers are mounted under the robot's axils and the sucker and wall are in non-contact. In order to pass obstacles, the sucker and the wheel unit can be pulled up and pushed down by a lifting mechanism. The magnetic adhesion force can be adjusted by changing the height of the gap between the sucker and the wall by the lifting mechanism. In order to increase the adhesion force, the value of the sucker's magnetic energy density (MED is maximized by optimizing the magnet sucker's structure parameters with a finite element method. Experiments prove that the magnetic adhesion mechanism has enough adhesion force and that the WCWR can complete wall-climbing work within a large unstructured environment.

  1. Nanoindentation of BaTiO3: dislocation nucleation and mechanical twinning

    International Nuclear Information System (INIS)

    Gaillard, Y; Anglada, M; MacIas, A Hurtado; Munoz-Saldana, J; Trapaga, G

    2009-01-01

    This paper presents a study of the deformation mechanisms of barium titanate under nanoindentation. The (0 0 1) and (1 1 0) crystallographic orientations of BaTiO 3 giant grains were indented and critical mean contact pressures for dislocation nucleation were extracted from the indentation curves. The orientation of the dislocation slip lines was identified by atomic force microscopy, showing that the (1 1 0){1 1 0} glide systems were activated. Twin bands, observed on both orientations, also occur on the {1 1 0} habit planes and actively participate in the accommodation of the plastic deformation. Furthermore, dislocation pile-ups introduced by spherical indentations have shown a close relation between dislocations and twinning formation.

  2. Subtalar dislocation

    International Nuclear Information System (INIS)

    El-Khoury, G.Y.; Yousefzadeh, D.K.; Mulligan, G.M.; Moore, T.E.

    1982-01-01

    Over a period of three years we have seen nine patients with subtalar dislocation, all of whom sustained violent trauma to the region of the ankle and hind foot. All but one patient were males. Clinically a subtalar dislocation resembles a complicated fracture dislocation of the ankle but a definitive diagnosis can only be made radiographically. The mechanism of injury and radiographic features of this injury are discussed. (orig.)

  3. CLIMBING WALL

    CERN Multimedia

    1999-01-01

    The FIRE AND RESCUE Group of TIS Commission informs that the climbing wall in the yard of the Fire-fighters Station, is intended for the sole use of the members of that service, and recalls that access to this installation is forbidden for safety reasons to all persons not belonging to the Service.CERN accepts no liability for damage or injury suffered as a result of failure to comply with this interdiction.TIS/DI

  4. Athermal mechanisms of size-dependent crystal flow gleaned from three-dimensional discrete dislocation simulations

    International Nuclear Information System (INIS)

    Rao, S.I.; Dimiduk, D.M.; Parthasarathy, T.A.; Uchic, M.D.; Tang, M.; Woodward, C.

    2008-01-01

    Recent experimental studies have revealed that micrometer-scale face-centered cubic (fcc) crystals show strong strengthening effects, even at high initial dislocation densities. We use large-scale three-dimensional discrete dislocation simulations (DDS) to explicitly model the deformation behavior of fcc Ni microcrystals in the size range of 0.5-20 μm. This study shows that two size-sensitive athermal hardening processes, beyond forest hardening, are sufficient to develop the dimensional scaling of the flow stress, stochastic stress variation, flow intermittency and high initial strain-hardening rates, similar to experimental observations for various materials. One mechanism, source-truncation hardening, is especially potent in micrometer-scale volumes. A second mechanism, termed exhaustion hardening, results from a breakdown of the mean-field conditions for forest hardening in small volumes, thus biasing the statistics of ordinary dislocation processes

  5. Dislocation-mediated strain hardening in tungsten: Thermo-mechanical plasticity theory and experimental validation

    Science.gov (United States)

    Terentyev, Dmitry; Xiao, Xiazi; Dubinko, A.; Bakaeva, A.; Duan, Huiling

    2015-12-01

    A self-consistent thermo-mechanical model to study the strain-hardening behavior of polycrystalline tungsten was developed and validated by a dedicated experimental route. Dislocation-dislocation multiplication and storage, as well dislocation-grain boundary (GB) pinning were the major mechanisms underlying the evolution of plastic deformation, thus providing a link between the strain hardening behavior and material's microstructure. The microstructure of the polycrystalline tungsten samples has been thoroughly investigated by scanning and electron microscopy. The model was applied to compute stress-strain loading curves of commercial tungsten grades, in the as-received and as-annealed states, in the temperature range of 500-1000 °C. Fitting the model to the independent experimental results obtained using a single crystal and as-received polycrystalline tungsten, the model demonstrated its capability to predict the deformation behavior of as-annealed samples in a wide temperature range and applied strain. The relevance of the dislocation-mediated plasticity mechanisms used in the model have been validated using transmission electron microscopy examination of the samples deformed up to different amounts of strain. On the basis of the experimental validation, the limitations of the model are determined and discussed.

  6. Evolution of nanoscale interstitial dislocation loops under coupling effect of stress and temperature

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Ning; Shen, Tielong; Kurtz, Richard; Wang, Zhiguang; Gao, Fei

    2017-07-01

    The properties of nano-scale interstitial dislocation loops under the coupling effect of stress and temperature are studied using atomistic simulation methods and experiments. The decomposition of a loop by the emission of smaller loops is identified as one of the major mechanisms to release the localized stress induced by the coupling effect, which is validated by the TEM observations. The classical conservation law of Burgers vector cannot be applied during such decomposition process. The dislocation network is formed from the decomposed loops, which may initiate the irradiation creep much earlier than expected through the mechanism of climb-controlled glide of dislocations.

  7. Significance of dislocations in the mechanism of Hadfield cast steel strengthening

    International Nuclear Information System (INIS)

    Stradomski, Z.; Morgiel, J.; Olszewski, J.

    1999-01-01

    The paper presents the results of microstructural examination of the adfield cast steel (L120G13 according to Polish Standards) strengthened by explosion method, which is an attractive alternative of the surface treatment of metal materials regarding its technological, economical and organizational aspects. The presented results have been obtained by means of qualitative and quantitative analysis of thin foils taken at different distances from the material surface being strengthened by single, double or triple detonation of 3 mm thick charges of explosive. The high pressure, order of 18 GPa, causes significant changes in dislocation structure of the austenite matrix. The strengthening of Hadfield cast steel during explosion is based on the increase of the dislocation density by several times as related to the supersaturated state and on the creation of dislocation bands consisting of short, densely tangled dislocations. Plastic deformation mechanisms i. e., slip lines and micro-twins, are definitively of minor importance. It has been also proved by means of the nuclear resonance method that the explosion do not cause changes in distribution of carbon atoms in the nearest neighbourhood of Fe atoms and that austenite is not transformed into the α-martensite or the hexagonal ε-phase. (author)

  8. High-temperature discrete dislocation plasticity

    Science.gov (United States)

    Keralavarma, S. M.; Benzerga, A. A.

    2015-09-01

    A framework for solving problems of dislocation-mediated plasticity coupled with point-defect diffusion is presented. The dislocations are modeled as line singularities embedded in a linear elastic medium while the point defects are represented by a concentration field as in continuum diffusion theory. Plastic flow arises due to the collective motion of a large number of dislocations. Both conservative (glide) and nonconservative (diffusion-mediated climb) motions are accounted for. Time scale separation is contingent upon the existence of quasi-equilibrium dislocation configurations. A variational principle is used to derive the coupled governing equations for point-defect diffusion and dislocation climb. Superposition is used to obtain the mechanical fields in terms of the infinite-medium discrete dislocation fields and an image field that enforces the boundary conditions while the point-defect concentration is obtained by solving the stress-dependent diffusion equations on the same finite-element grid. Core-level boundary conditions for the concentration field are avoided by invoking an approximate, yet robust kinetic law. Aspects of the formulation are general but its implementation in a simple plane strain model enables the modeling of high-temperature phenomena such as creep, recovery and relaxation in crystalline materials. With emphasis laid on lattice vacancies, the creep response of planar single crystals in simple tension emerges as a natural outcome in the simulations. A large number of boundary-value problem solutions are obtained which depict transitions from diffusional to power-law creep, in keeping with long-standing phenomenological theories of creep. In addition, some unique experimental aspects of creep in small scale specimens are also reproduced in the simulations.

  9. Multifunctional Alloys Obtained via a Dislocation-Free Plastic Deformation Mechanism.

    Science.gov (United States)

    Saito, Takashi; Furuta, Tadahiko; Hwang, Jung-Hwan; Kuramoto, Shigeru; Nishino, Kazuaki; Suzuki, Nobuaki; Chen, Rong; Yamada, Akira; Ito, Kazuhiko; Seno, Yoshiki; Nonaka, Takamasa; Ikehata, Hideaki; Nagasako, Naoyuki; Iwamoto, Chihiro; Ikuhara, Yuuichi; Sakuma, Taketo

    2003-04-18

    We describe a group of alloys that exhibit "super" properties, such as ultralow elastic modulus, ultrahigh strength, super elasticity, and super plasticity, at room temperature and that show Elinvar and Invar behavior. These "super" properties are attributable to a dislocation-free plastic deformation mechanism. In cold-worked alloys, this mechanism forms elastic strain fields of hierarchical structure that range in size from the nanometer scale to several tens of micrometers. The resultant elastic strain energy leads to a number of enhanced material properties.

  10. Mechanical properties of nano and bulk Fe pillars using molecular dynamics and dislocation dynamics simulation

    Science.gov (United States)

    Nath, S. K. Deb

    2017-10-01

    Using molecular dynamics simulation, tension and bending tests of a Fe nanopillar are carried out to obtain its Young's modulus and yield strength. Then the comparative study of Young's modulus and yield strength of a Fe nanopillar under bending and tension are carried out varying its diameter in the range of diameter 1-15nm. We find out the reasons why bending Young's modulus and yield strength of a Fe nanopillar are higher than those of tension Young's modulus and yield strength of a Fe nanopillar. Using the mobility parameters of bulk Fe from the experimental study [N. Urabe and J. Weertman, Materials Science and Engineering 18, 41 (1975)], its temperature dependent stress-strain relationship, yield strength and strain hardening modulus are obtained from the dislocation dynamics simulations. Strain rate dependent yield strength and strain hardening modulus of bulk Fe pillars under tension are studied. Temperature dependent creep behaviors of bulk Fe pillars under tension are also studied. To verify the soundness of the present dislocation dynamics studies of the mechanical properties of bulk Fe pillars under tension, the stress vs. strain relationship and dislocation density vs. strain of bulk Fe pillars obtained by us are compared with the published results obtained by S. Queyreau, G. Monnet, and B. Devincre, International Journal of Plasticity 25, 361 (2009).

  11. Low-temperature embrittlement and fracture of metals with different crystal lattices – Dislocation mechanisms

    Directory of Open Access Journals (Sweden)

    V.M. Chernov

    2016-12-01

    Full Text Available The state of a low-temperature embrittlement (cold brittleness and dislocation mechanisms for formation of the temperature of a ductile-brittle transition and brittle fracture of metals (mono- and polycrystals with various crystal lattices (BCC, FCC, HCP are considered. The conditions for their formation connected with a stress-deformed state and strength (low temperature yield strength as well as the fracture breaking stress and mobility of dislocations in the top of a crack of the fractured metal are determined. These conditions can be met for BCC and some HCP metals in the initial state (without irradiation and after a low-temperature damaging (neutron irradiation. These conditions are not met for FCC and many HCP metals. In the process of the damaging (neutron irradiation such conditions are not met also and the state of low-temperature embrittlement of metals is absent (suppressed due to arising various radiation dynamic processes, which increase the mobility of dislocations and worsen the strength characteristics.

  12. Effect of collision cascades on dislocations in tungsten: A molecular dynamics study

    Energy Technology Data Exchange (ETDEWEB)

    Fu, B.Q., E-mail: bqfu@scu.edu.cn [Key Laboratory for Radiation Physics and Technology, Institute of Nuclear Science and Technology, Sichuan University, Chengdu 610065 (China); Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Fitzgerald, S.P. [Department of Applied Mathematics, University of Leeds, Leeds LS2 9JT (United Kingdom); Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Hou, Q.; Wang, J.; Li, M. [Key Laboratory for Radiation Physics and Technology, Institute of Nuclear Science and Technology, Sichuan University, Chengdu 610065 (China)

    2017-02-15

    Highlights: • A cascde near a dislocation promotes climb motion. • Kinks induced by cascade facilitate the dipoles motion toward the cascade. • Shearing of dipole is dependent on PKA energy, position, direction, and dipole width. - Abstract: Tungsten (W) is the prime candidate material for the divertor and other plasma-facing components in DEMO. The point defects (i.e. vacancies and self-interstitials) produced in collision cascades caused by incident neutrons aggregate into dislocation loops (and voids), which strongly affect the mechanical properties. The point defects also interact with existing microstructural features, and understanding these processes is crucial for modelling the long term microstructural evolution of the material under fusion conditions. In this work, we performed molecular dynamics simulations of cascades interacting with initially straight edge dislocation dipoles. It was found that the residual vacancy number usually exceeds the residual interstitial number for cascades interacting with vacancy type dipoles, but for interstitial type dipoles these are close. We observed that a cascade near a dislocation promotes climb, i.e. it facilitates the movement of point defects along the climb direction. We also observed that the dislocations move easily along the glide direction, and that kinks are formed near the centre of the cascade, which then facilitate the movement of the dipoles. Some dipoles are sheared off by the cascade, and this is dependent on PKA energy, position, direction, and the width of dipole.

  13. Perilunate Dislocation

    Directory of Open Access Journals (Sweden)

    John Jiao

    2016-09-01

    Full Text Available History of present illness: A 25-year-old female presented to the emergency department with left wrist pain following a fall off a skateboard. The patient fell on her outstretched left wrist with the wrist dorsiflexed and reported immediate sharp pain to her left wrist that was worse with movement. She denied other trauma. Significant findings: In the left lateral wrist x-ray, the lunate (outlined in blue is dislocated from the rest of the wrist bones (yellow line but still articulates with the radius (red line. The capitate (yellow line does not sit within the distal articulation of the lunate and is displaced dorsally. Additionally, a line drawn through the radius and lunate (green line fails to intersect with the capitate. This is consistent with a perilunate dislocation. This is compared to a lunate dislocation, where the lunate itself is displaced and turned ventrally (spilled teacup and the proximal aspect does not articulate with the radius. Discussion: A perilunate dislocation is a significant closed wrist injury that is easily missed on standard anterior-posterior imaging. These dislocations are relatively rare, involving only 7% of all carpal injuries and are associated with high-energy trauma onto a hyperextended wrist, such as falls from a height, motor vehicle accidents, and sports injuries.1 An untreated perilunate dislocation is associated with high risk of chronic carpal instability and post-traumatic arthritis. If the mechanism of injury is sufficient to suspect perilunate dislocation, multiple radiographic views of the wrist should be ordered. Patients should receive prompt orthopedic consultation for open reduction and ligamentous repair. Even after successful identification and subsequent surgical repair, median nerve neuropathy and post-traumatic arthritis are frequent.2-3

  14. Molecular dynamics study on the evolution of interfacial dislocation network and mechanical properties of Ni-based single crystal superalloys

    Science.gov (United States)

    Li, Nan-Lin; Wu, Wen-Ping; Nie, Kai

    2018-05-01

    The evolution of misfit dislocation network at γ /γ‧ phase interface and tensile mechanical properties of Ni-based single crystal superalloys at various temperatures and strain rates are studied by using molecular dynamics (MD) simulations. From the simulations, it is found that with the increase of loading, the dislocation network effectively inhibits dislocations emitted in the γ matrix cutting into the γ‧ phase and absorbs the matrix dislocations to strengthen itself which increases the stability of structure. Under the influence of the temperature, the initial mosaic structure of dislocation network gradually becomes irregular, and the initial misfit stress and the elastic modulus slowly decline as temperature increasing. On the other hand, with the increase of the strain rate, it almost has no effect on the elastic modulus and the way of evolution of dislocation network, but contributes to the increases of the yield stress and tensile strength. Moreover, tension-compression asymmetry of Ni-based single crystal superalloys is also presented based on MD simulations.

  15. Mechanism and patterns of cervical spine fractures-dislocations in vertebral artery injury

    Directory of Open Access Journals (Sweden)

    Pankaj Gupta

    2012-01-01

    Full Text Available Purpose: To identify the fracture patterns and mechanism of injury, based on subaxial cervical spine injury classification system (SLIC, on non-contrast computed tomography (NCCT of cervical spine predictive of vertebral artery injury (VAI. Patients and Methods: We retrospectively analyzed cervical spine magnetic resonance imaging (MRI of 320 patients who were admitted with cervical spine injury in our level I regional trauma center over a period of two years (April 2010 to April 2012. Diagnosis of VAI was based on hyperintensity replacing the flow void on a T2-weighted axial image. NCCT images of the selected 43 patients with MRI diagnosis of VAI were then assessed for the pattern of injury. The cervical spinal injuries were classified into those involving the C1 and C2 and subaxial spine. For the latter, SLIC was used. Results: A total of 47 VAI were analyzed in 43 patients. Only one patient with VAI on MRI had no detectable abnormality on NCCT. C1 and C2 injuries were found in one and six patients respectively. In subaxial injuries, the most common mechanism of injury was distraction (37.5% with facet dislocation with or without fracture representing the most common pattern of injury (55%. C5 was the single most common affected vertebral level. Extension to foramen transversarium was present in 20 (42.5% cases. Conclusion: CT represents a robust screening tool for patients with VAI. VAI should be suspected in patients with facet dislocation with or without fractures, foramina transversarium fractures and C1-C3 fractures, especially type III odontoid fractures and distraction mechanism of injury.

  16. Lunate Dislocation

    Directory of Open Access Journals (Sweden)

    Jonathan Peña

    2017-01-01

    Full Text Available History of present illness: A 28-year-old right-handed male presented to the ED after he fell onto his outstretched right hand after being thrown from his motorcycle at highway speeds. He complained of right wrist pain. On exam, he had a visible deformity of his right wrist with diffuse tenderness to palpation over the wrist. Sensation was intact and he had 2+ radial and ulnar pulses. Significant findings: Plain film of the right wrist showed the classic “spilled teacup” consistent with a lunate dislocation. There is a loss of the normal articulation between the distal radius and lunate (white curved highlights represent expected points of articulation. Discussion: The most common mechanism leading to a dislocation of lunate is a fall onto an outstretched hand with the wrist in extension. Damage to the ligamentous infrastructure (commonly the dorsal radiolunate ligament causes destabilization.1 Lunate dislocations are distinguished from perilunate dislocations by assessing for the preservation of the articulation between the lunate and distal radius. In lunate dislocations, this articulation is disrupted leading to the classic “spilled teacup” appearance as seen above. However, if the articulation between the distal radius and lunate is preserved, but there is displacement of the carpal bones (eg, scaphoid, triquetrum, etc, then the dislocation is referred to as a perilunate dislocation. Plain film radiography oriented in the lateral view is typically the first-line modality for diagnosis. However, advanced imaging such as computed tomography or magnetic resonance imaging may be required to rule out fracture. It is important to keep in mind that the lunate receives its blood supply distally from the anterior interosseous artery; therefore, any injury (eg, fracture that disrupts perfusion places the patient at risk for avascular necrosis.2 As with all orthopedic upper extremity injuries, a thorough neurologic exam should be performed

  17. Dislocation following total knee arthroplasty: A report of six cases

    Directory of Open Access Journals (Sweden)

    Villanueva Manuel

    2010-01-01

    Full Text Available Background: Dislocation following total knee arthroplasty (TKA is the worst form of instability. The incidence is from 0.15 to 0.5%. We report six cases of TKA dislocation and analyze the patterns of dislocation and the factors related to each of them. Materials and Methods: Six patients with dislocation of knee following TKA are reported. The causes for the dislocations were an imbalance of the flexion gap (n=4, an inadequate selection of implants (n=1, malrotation of components (n=1 leading to incompetence of the extensor mechanism, or rupture of the medial collateral ligament (MCC. The patients presented complained of pain, giving way episodes, joint effusion and difficulty in climbing stairs. Five patients suffered posterior dislocation while one anterior dislocation. An urgent closed reduction of dislocation was performed under general anaesthesia in all patients. All patients were operated for residual instability by revision arthroplasty after a period of conservative treatment. Results: One patient had deep infection and knee was arthrodesed. Two patients have a minimal residual lag for active extension, including a patient with a previous patellectomy. Result was considered excellent or good in four cases and fair in one, without residual instability. Five out of six patients in our series had a cruciate retaining (CR TKA designs: four were revised to a posterior stabilized (PS TKA and one to a rotating hinge design because of the presence of a ruptured MCL. Conclusion: Further episodes of dislocation or instability will be prevented by identifying and treating major causes of instability. The increase in the level of constraint and correction of previous technical mistakes is mandatory.

  18. Mechanisms operating during plastic deformation of metals under concurrent production of cascades and dislocations

    DEFF Research Database (Denmark)

    Trinkaus, H.; Singh, Bachu Narain

    solutions of the kinetic equations are discussed. The apparent memory of the system for the pre-yield dose is identified as the result of simultaneous and closely parallel transient evolutions of the cascade damage and the dislocations up to the end of the IRTs. The contributions of dislocation decoration...

  19. Mechanisms operating during plastic deformation of metals under concurrent production of cascades and dislocations

    International Nuclear Information System (INIS)

    Trinkaus, H.; Singh, B.N.

    2008-04-01

    Recent in-reactor tensile tests (IRTs) on pure copper have revealed a deformation behaviour which is significantly different from that observed in post-irradiation tensile tests (PITs). In IRTs, the material deforms uniformly and homogeneously without yield drop and plastic instability as commonly observed in PITs. An increase in the pre-yield dose results in an increase in the level of hardening over the whole test periods and a decrease in the uniform elongation suggesting that the materials 'remember' the impact of the pre-yield damage level. These features are modelled in terms of the decoration of dislocations with glissile dislocation loops. During pre-yield irradiation, dislocation decoration is due to the one-dimensional (1D) diffusion of cascade induced self-interstitial (SIA) clusters and their trapping in the stress field of the static grown-in dislocations. During post-yield irradiation and deformation, moving dislocations are decorated by the sweeping of matrix loops. The interaction of dislocations with loops and between loops is discussed as a function of the relevant parameters. On this basis, the kinetics of decoration is treated in terms of fluxes of loops to and reactions with each other in a conceived 2D space of decoration. In this space, loop coalescence, alignment and mutual blocking reactions are characterised by appropriate reaction cross sections. In the kinetic equations for 'dynamic decoration' under deformation, the evolution of the dislocation density is taken into account. Simple solutions of the kinetic equations are discussed. The apparent memory of the system for the pre-yield dose is identified as the result of simultaneous and closely parallel transient evolutions of the cascade damage and the dislocations up to the end of the IRTs. The contributions of dislocation decoration to yield and flow stresses are attributed to the interaction of dislocations with aligned loops temporarily or permanently immobilized by other loops or

  20. Mechanisms operating during plastic deformation of metals under concurrent production of cascades and dislocations

    Energy Technology Data Exchange (ETDEWEB)

    Trinkaus, H. [Institut fuer Festkoerperforschung, Forschungszentrum Juelich (Germany); Singh, B.N. [Technical Univ. of Denmark, Risoe National Laboratory for Sustainable Energy, Materials Research Dept., Roskilde (Denmark)

    2008-04-15

    Recent in-reactor tensile tests (IRTs) on pure copper have revealed a deformation behaviour which is significantly different from that observed in post-irradiation tensile tests (PITs). In IRTs, the material deforms uniformly and homogeneously without yield drop and plastic instability as commonly observed in PITs. An increase in the pre-yield dose results in an increase in the level of hardening over the whole test periods and a decrease in the uniform elongation suggesting that the materials 'remember' the impact of the pre-yield damage level. These features are modelled in terms of the decoration of dislocations with glissile dislocation loops. During pre-yield irradiation, dislocation decoration is due to the one-dimensional (1D) diffusion of cascade induced self-interstitial (SIA) clusters and their trapping in the stress field of the static grown-in dislocations. During post-yield irradiation and deformation, moving dislocations are decorated by the sweeping of matrix loops. The interaction of dislocations with loops and between loops is discussed as a function of the relevant parameters. On this basis, the kinetics of decoration is treated in terms of fluxes of loops to and reactions with each other in a conceived 2D space of decoration. In this space, loop coalescence, alignment and mutual blocking reactions are characterised by appropriate reaction cross sections. In the kinetic equations for 'dynamic decoration' under deformation, the evolution of the dislocation density is taken into account. Simple solutions of the kinetic equations are discussed. The apparent memory of the system for the pre-yield dose is identified as the result of simultaneous and closely parallel transient evolutions of the cascade damage and the dislocations up to the end of the IRTs. The contributions of dislocation decoration to yield and flow stresses are attributed to the interaction of dislocations with aligned loops temporarily or permanently immobilized

  1. Environmental effects on deformation mechanism and dislocation microstructure in fatigued copper single crystal

    International Nuclear Information System (INIS)

    Yang, J.H.; Zhang, X.P.; Mai, Y.-W.; Jia, W.P.; Ke, W.

    2005-01-01

    The deformation and dislocation microstructure of a [0 1 3] double-slip-oriented copper single crystal under a symmetric tension-compression cyclic load were characterized at room temperature in open-air and a neutral 0.5 M NaCl aqueous solution, respectively. The surface morphology of deformed specimens and the dislocation structures at saturation stage of cyclic deformation were observed using scanning electron microscopy (SEM) by the electron channeling contrast (ECC) technique and transmission electron microscopy (TEM). The results show that the saturation dislocation structures during the corrosion fatigue in the 0.5 M NaCl aqueous solution mainly consist of labyrinth, wall and vein dislocation microstructures, as well as deformation twins, which differ from the wall and vein dislocation structures in open-air environment. More importantly, here we report TEM observations that provide evidence of deformation twinning in the [0 1 3] double-slip-oriented copper single crystal during corrosion fatigue at room temperature and a very slow strain rate, which was generally only observed at sub-ambient temperature and/or high strain rate conditions

  2. Dislocation model of fracture

    International Nuclear Information System (INIS)

    Kull', L.M.

    1987-01-01

    Papers dealing with study on mechanisms of submicricrack formation and propagation using dislocation representations are analyzed. Cases of brittle and ductile fracture of materials as well as models of dislocationless (amorphous) zone at the growing crack tip are considered. Dislocation models of fracture may be used when studying the processes of deformation and accumulation of damages in elements of nuclear facilities

  3. Radiation-Enhanced Dislocation Glide: The Current Status of Research

    Science.gov (United States)

    Maeda, Koji

    Dislocations in most semiconductors exhibit radiation-enhanced dislocation glide (REDG) which is a cause of serious degradation in bipolar devices under forward biasing. Phenomenologically, REDG is characterized by the remarkable reduction of activation energy for glide velocity and the pre-exponential factor controlled by radiation intensity. Although the REDG shares features common with similar effects in point defects known as the recombination-enhanced defect reaction (REDR) that is well interpreted in terms of the phonon kick mechanism, it is not as yet established whether the REDG and the REDR share or not the same microscopic mechanism due to the lack of knowledge concerning electronic levels associated with the dislocations showing the REDG. Recent progress, however, has been achieved by studies of REDG in 4H-silicon carbide (4H-SiC) in which the dislocation component that exhibits the REDG is identified as 30°-Si(g) partial dislocation. Nevertheless, the driving force for the REDG in 4H-SiC is not the mechanical stress as in usual cases but an anomalous reversal of the sign of the Shockley stacking-fault (SSF) energy depending on the radiation intensity. An attempt was made in our recent experiments of photoinduced REDG to separate the intensity-dependent REDG effect and also the intensity-dependent driving force by simultaneous measurements of SSF expansion velocity (hence, the glide velocity of 30°-Si(g) partials) and the intensity of photoluminescence from the same SSFs (the latter allows us to deduce the driving force for the SSF expansion and hence the REDG). A comment, inspired by the studies of REDG in 4H-SiC, is given also to the mechanism of radiation-enhanced dislocation climb, another cause of degradation induced by minority-carrier injection.

  4. Atlantooccipital dislocation in motor vehicle side impact, derivation of the mechanism of injury, and implications for early diagnosis

    Directory of Open Access Journals (Sweden)

    Kevin M Smith

    2010-01-01

    Full Text Available Numerous reports of atlantooccipital dislocations (AODs have been described in frontal impacts and vehicle versus pedestrian collisions. Reports of survival after AOD in conjunction with side impacts have infrequently been reported in the literature. The objective of this study is to present a case of an AOD from a side impact vehicle collision, and deduce the mechanism of injury. A clinical and biomechanical reconstruction of the collision was performed to investigate the mechanism of the dislocation. A 51-year-old female was traveling in a four-door sedan and sustained a side impact collision with a compact pickup truck. At the time of extrication, the patient was neurologically intact with a Glasgow Coma Scale score of 15. After admittance to the hospital, the patient developed a decline in respiratory status, right mild hemiparesis, and left sixth-nerve palsy, and magnetic resonance imaging (MRI and computed tomography (CT reconstructions indicated a craniocervical dislocation. Surgical fixation was performed and all extra-axial hemorrhaging was evacuated. At discharge, the patient was neurologically intact on the left side, had right mild hemiparesis, left sixth-nerve palsy, and minor dysarthria. Survival rates of AODs have recently been increasing. Morbidity is still more prevalent, however. Due to the variety of symptoms that accompany AODs and the inconsistency of diagnostic imaging techniques, a thorough history of the etiology may lead to increased clinical suspicion of this injury and further raise survival rates.

  5. Atlantooccipital dislocation in motor vehicle side impact, derivation of the mechanism of injury, and implications for early diagnosis.

    Science.gov (United States)

    Smith, Kevin M; Yoganandan, Narayan; Pintar, Frank A; Kurpad, Shekar N; Maiman, Dennis J

    2010-07-01

    Numerous reports of atlantooccipital dislocations (AODs) have been described in frontal impacts and vehicle versus pedestrian collisions. Reports of survival after AOD in conjunction with side impacts have infrequently been reported in the literature. The objective of this study is to present a case of an AOD from a side impact vehicle collision, and deduce the mechanism of injury. A clinical and biomechanical reconstruction of the collision was performed to investigate the mechanism of the dislocation. A 51-year-old female was traveling in a four-door sedan and sustained a side impact collision with a compact pickup truck. At the time of extrication, the patient was neurologically intact with a Glasgow Coma Scale score of 15. After admittance to the hospital, the patient developed a decline in respiratory status, right mild hemiparesis, and left sixth-nerve palsy, and magnetic resonance imaging (MRI) and computed tomography (CT) reconstructions indicated a craniocervical dislocation. Surgical fixation was performed and all extra-axial hemorrhaging was evacuated. At discharge, the patient was neurologically intact on the left side, had right mild hemiparesis, left sixth-nerve palsy, and minor dysarthria. Survival rates of AODs have recently been increasing. Morbidity is still more prevalent, however. Due to the variety of symptoms that accompany AODs and the inconsistency of diagnostic imaging techniques, a thorough history of the etiology may lead to increased clinical suspicion of this injury and further raise survival rates.

  6. Research on Dynamics and Stability in the Stairs-Climbing of a Tracked Mobile Robot

    Directory of Open Access Journals (Sweden)

    Weijun Tao

    2012-10-01

    Full Text Available Aiming at the functional requirement of climbing up the stairs, the dynamics and stability during a tracked mobile robot's climbing of stairs is studied. First, from the analysis of its cross-country performance, the mechanical structure of the tracked mobile robot is designed and the hardware composition of its control system is given. Second, based on the analysis to its stairs-climbing process, the dynamical model of stairs-climbing is established by using the classical mechanics method. Next, the stability conditions for its stairs-climbing are determined and an evaluation method of its stairs-climbing stability is proposed, based on a mechanics analysis on the robot's backwards tumbling during the stairs-climbing process. Through simulation and experiments, the effectiveness of the dynamical model and the stability evaluation method of the tracked mobile robot in stairs-climbing is verified, which can provide design and analysis foundations for the tracked mobile robots' stairs-climbing.

  7. Climbing injuries among children and youth

    OpenAIRE

    Ginszt, Michał; Goniewicz, Mariusz; Ginszt, Apolinary; Goniewicz, Krzysztof

    2011-01-01

    Sport climbing is one of the most popular extreme sports, but also a sport of high traumatism. During climbing movement, the main effort is made by the upper limbs and the biggest load is put on them. Fingers, which keep handholds, are exposed to injuries of tendons, tendon sheaths and straps. Muscles which work at the movement of the elbow joint, work under the load of the whole body and can be overstrained. The paper presents causes and mechanisms of injuries rises in children and teenagers...

  8. Jaw Dislocation

    Science.gov (United States)

    ... used to temporarily stabilize the jaw after a fracture or dislocation. More Information Mouth Healthy Resources In This Article Figure 1 Putting a Dislocated Jaw Back in Place Figure 2 Barton Bandage Urgent Dental Problems Introduction to Urgent Dental Problems Fractured, Loosened, ...

  9. Fibrillar Adhesive for Climbing Robots

    Science.gov (United States)

    Pamess, Aaron; White, Victor E.

    2013-01-01

    A climbing robot needs to use its adhesive patches over and over again as it scales a slope. Replacing the adhesive at each step is generally impractical. If the adhesive or attachment mechanism cannot be used repeatedly, then the robot must carry an extra load of this adhesive to apply a fresh layer with each move. Common failure modes include tearing, contamination by dirt, plastic deformation of fibers, and damage from loading/ unloading. A gecko-like fibrillar adhesive has been developed that has been shown useful for climbing robots, and may later prove useful for grasping, anchoring, and medical applications. The material consists of a hierarchical fibrillar structure that currently contains two levels, but may be extended to three or four levels in continuing work. The contacting level has tens of thousands of microscopic fibers made from a rubberlike material that bend over and create intimate contact with a surface to achieve maximum van der Waals forces. By maximizing the real area of contact that these fibers make and minimizing the bending energy necessary to achieve that contact, the net amount of adhesion has been improved dramatically.

  10. Towards a quantification of stress corrosion mechanisms: numerical simulations of hydrogen-dislocations at the very crack tip; Vers une quantification des mecanismes de corrosion sous contrainte: simulations numeriques des interactions hydrogene-dislocations en pointe de fissure

    Energy Technology Data Exchange (ETDEWEB)

    Chateau, J.P

    1999-01-05

    We discuss the respective roles played by anodic dissolution and hydrogen in SCC mechanisms of f.c.c. materials, by studying the fracture of copper in nitrite for which we compare the results with that previously obtained in 316L steel in hot chloride. It is surprising to note that even the crystallographies at the scale of the micron are different, the macroscopic inclination of the fracture surfaces are the same. In the case of 316L steel, the formation of strong pile-ups in the presence of hydrogen leads to a zigzag fracture along alternated slip planes in the most general case. In the absence of hydrogen, as in copper, this mechanism effectively disappears. Furthermore, numerical simulations of crack shielding by dislocations emitted on one plane predict the macroscopic inclination. It shows that it is due to the mere dissolution which confines slip activity at the very crack tip in f.c.c. materials. In order to quantify the mechanism involved in 316L steel, we developed simulations which numerically solve the coupled diffusion and elasticity equations for hydrogen in the presence of a crack and shielding dislocations. They reproduce the mechanisms of hydrogen segregation on edge dislocations and of a localised softening effect by decreasing pair interactions. These mechanisms lead to i) a localisation of hydrogen embrittlement along the activated slip planes, ii) an increase of the dislocation density in pile-ups, and iii) a decrease of the cross slip probability. These three factors enhance micro-fracture at the head of a pile-up, which is responsible of thezigzag fracture. Introducing the free surface effects for hydrogen, we point out a new mechanism: the inhibition of dislocation sources at the crack tip, which is relevant with the brittle fracture surfaces observed in some cases in 316L steel. The quantification of these different mechanisms allows to give a relation between the local fracture possibility and the macroscopic parameters. A general law for

  11. Electronic properties of dislocations introduced mechanically at room temperature on a single crystal silicon surface

    International Nuclear Information System (INIS)

    Ogawa, Masatoshi; Kamiya, Shoji; Izumi, Hayato; Tokuda, Yutaka

    2012-01-01

    This paper focuses on the effects of temperature and environment on the electronic properties of dislocations in n-type single crystal silicon near the surface. Deep level transient spectroscopy (DLTS) analyses were carried out with Schottky electrodes and p + -n junctions. The trap level, originally found at E C -0.50 eV (as commonly reported), shifted to a shallower level at E C -0.23 eV after a heat treatment at 350 K in an inert environment. The same heat treatment in lab air, however, did not cause any shift. The trap level shifted by the heat treatment in an inert environment was found to revert back to the original level when the specimens were exposed to lab air again. Therefore, the intrinsic trap level is expected to occur at E C -0.23 eV and shift sensitively with gas adsorption in air.

  12. Formation of disorientations in dislocation structures during plastic deformation

    DEFF Research Database (Denmark)

    Pantleon, W.

    2002-01-01

    Disorientations developing during plastic deformation in dislocation structures are investigated. Based on expected mechanisms for the formation of different types of dislocation boundaries (statistical trapping of dislocations or differently activated slip systems) the formation of the disorient......Disorientations developing during plastic deformation in dislocation structures are investigated. Based on expected mechanisms for the formation of different types of dislocation boundaries (statistical trapping of dislocations or differently activated slip systems) the formation...

  13. Preparticipation Evaluation for Climbing Sports.

    Science.gov (United States)

    Campbell, Aaron D; Davis, Christopher; Paterson, Ryan; Cushing, Tracy A; Ng, Pearlly; Peterson, Charles S; Sedgwick, Peter E; McIntosh, Scott E

    2015-12-01

    Climbing is a popular wilderness sport among a wide variety of professional athletes and amateur enthusiasts, and many styles are performed across many environments. Potential risks confront climbers, including personal health or exacerbation of a chronic condition, in addition to climbing-specific risks or injuries. Although it is not common to perform a preparticipation evaluation (PPE) for climbing, a climber or a guide agency may request such an evaluation before participation. Formats from traditional sports PPEs can be drawn upon, but often do not directly apply. The purpose of this article was to incorporate findings from expert opinion from professional societies in wilderness medicine and in sports medicine, with findings from the literature of both climbing epidemiology and traditional sports PPEs, into a general PPE that would be sufficient for the broad sport of climbing. The emphasis is on low altitude climbing, and an overview of different climbing styles is included. Knowledge of climbing morbidity and mortality, and a standardized approach to the PPE that involves adequate history taking and counseling have the potential for achieving risk reduction and will facilitate further study on the evaluation of the efficacy of PPEs. Copyright © 2015. Published by Elsevier Inc.

  14. Climbing the Needs Pyramids

    Directory of Open Access Journals (Sweden)

    J. C. Lomas

    2013-08-01

    Full Text Available Abraham Maslow’s theory of human adult motivation is often represented by a pyramid image showing two proposals: First, the five needs stages in emergent order of hierarchical ascension and second, a percentage of the adult population suggested to occupy each needs tier. Specifically, Maslow proposed that adults would be motivated to satisfy their unfilled needs until they reached the hierarchy’s apex and achieved self-transcendence. Yet how adults can purposefully ascend Maslow’s pyramid through satisfying unfilled needs remains elusive. This brief article challenges this on the theory’s 70th anniversary by presenting a new image of the needs hierarchy, based on ecological design principles to support adults’ purposeful endeavors to climb the needs pyramid.

  15. Mechanical properties of ceria nanorods and nanochains; the effect of dislocations, grain-boundaries and oriented attachment.

    Science.gov (United States)

    Sayle, Thi X T; Inkson, Beverley J; Karakoti, Ajay; Kumar, Amit; Molinari, Marco; Möbus, Günter; Parker, Stephen C; Seal, Sudipta; Sayle, Dean C

    2011-04-01

    We predict that the presence of extended defects can reduce the mechanical strength of a ceria nanorod by 70%. Conversely, the pristine material can deform near its theoretical strength limit. Specifically, atomistic models of ceria nanorods have been generated with full microstructure, including: growth direction, morphology, surface roughening (steps, edges, corners), point defects, dislocations and grain-boundaries. The models were then used to calculate the mechanical strength as a function of microstructure. Our simulations reveal that the compressive yield strengths of ceria nanorods, ca. 10 nm in diameter and without extended defects, are 46 and 36 GPa for rods oriented along [211] and [110] respectively, which represents almost 10% of the bulk elastic modulus and are associated with yield strains of about 0.09. Tensile yield strengths were calculated to be about 50% lower with associated yield strains of about 0.06. For both nanorods, plastic deformation was found to proceed via slip in the {001} plane with direction --a primary slip system for crystals with the fluorite structure. Dislocation evolution for the nanorod oriented along [110] was nucleated via a cerium vacancy present at the surface. A nanorod oriented along [321] and comprising twin-grain boundaries with {111} interfacial planes was calculated to have a yield strength of about 10 GPa (compression and tension) with the grain boundary providing the vehicle for plastic deformation, which slipped in the plane of the grain boundary, with an associated slip direction. We also predict, using a combination of atomistic simulation and DFT, that rutile-structured ceria is feasible when the crystal is placed under tension. The mechanical properties of nanochains, comprising individual ceria nanoparticles with oriented attachment and generated using simulated self-assembly, were found to be similar to those of the nanorod with grain-boundary. Images of the atom positions during tension and compression

  16. Dislocation-based plasticity and strengthening mechanisms in sub-20 nm lamellar structures in pearlitic steel wire

    DEFF Research Database (Denmark)

    Zhang, Xiaodan; Hansen, Niels; Godfrey, Andrew

    2016-01-01

    The tensile properties and the deformation microstructure of pearlitic steel (0.8 wt % C) have been quantified in wires drawn to strains in the range from 3.7 to 5.4, having a flow stress in the range from 3.5 to 4.5 GPa. With increasing strain the interlamellar spacing (ILS) decreases from about...... at a strain of 5.4; the dislocations are stored as threading dislocations, as dislocation tangles and as cell boundaries with low to medium misorientation angles. An analysis of the evolution of microstructure and strength with increasing strain suggests that dislocation-based plasticity is a dominating...... the calculated and the measured flow stress is observed over the strain range 0e5.4. However at large strains beyond 3.7 deviations are observed which are discussed in terms of the applied strength-structure relationships....

  17. Bouldering: an alternative strategy to long-vertical climbing in root-climbing hortensias.

    Science.gov (United States)

    Granados Mendoza, Carolina; Isnard, Sandrine; Charles-Dominique, Tristan; Van den Bulcke, Jan; Rowe, Nick P; Van Acker, Joris; Goetghebeur, Paul; Samain, Marie-Stéphanie

    2014-10-06

    In the Neotropics, the genus Hydrangea of the popular ornamental hortensia family is represented by climbing species that strongly cling to their support surface by means of adhesive roots closely positioned along specialized anchoring stems. These root-climbing hortensia species belong to the nearly exclusive American Hydrangea section Cornidia and generally are long lianescent climbers that mostly flower and fructify high in the host tree canopy. The Mexican species Hydrangea seemannii, however, encompasses not only long lianescent climbers of large vertical rock walls and coniferous trees, but also short 'shrub-like' climbers on small rounded boulders. To investigate growth form plasticity in root-climbing hortensia species, we tested the hypothesis that support variability (e.g. differences in size and shape) promotes plastic responses observable at the mechanical, structural and anatomical level. Stem bending properties, architectural axis categorization, tissue organization and wood density were compared between boulder and long-vertical tree-climbers of H. seemannii. For comparison, the mechanical patterns of a closely related, strictly long-vertical tree-climbing species were investigated. Hydrangea seemannii has fine-tuned morphological, mechanical and anatomical responses to support variability suggesting the presence of two alternative root-climbing strategies that are optimized for their particular environmental conditions. Our results suggest that variation of some stem anatomical traits provides a buffering effect that regulates the mechanical and hydraulic demands of two distinct plant architectures. The adaptive value of observed plastic responses and the importance of considering growth form plasticity in evolutionary and conservation studies are discussed. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

  18. Evolutionary Novelty versus Exaptation: Oral Kinematics in Feeding versus Climbing in the Waterfall-Climbing Hawaiian Goby Sicyopterus stimpsoni

    Science.gov (United States)

    Cullen, Joshua A.; Maie, Takashi; Schoenfuss, Heiko L.; Blob, Richard W.

    2013-01-01

    Species exposed to extreme environments often exhibit distinctive traits that help meet the demands of such habitats. Such traits could evolve independently, but under intense selective pressures of extreme environments some existing structures or behaviors might be coopted to meet specialized demands, evolving via the process of exaptation. We evaluated the potential for exaptation to have operated in the evolution of novel behaviors of the waterfall-climbing gobiid fish genus Sicyopterus. These fish use an “inching” behavior to climb waterfalls, in which an oral sucker is cyclically protruded and attached to the climbing surface. They also exhibit a distinctive feeding behavior, in which the premaxilla is cyclically protruded to scrape diatoms from the substrate. Given the similarity of these patterns, we hypothesized that one might have been coopted from the other. To evaluate this, we filmed climbing and feeding in Sicyopterus stimpsoni from Hawai’i, and measured oral kinematics for two comparisons. First, we compared feeding kinematics of S. stimpsoni with those for two suction feeding gobiids (Awaous guamensis and Lentipes concolor), assessing what novel jaw movements were required for algal grazing. Second, we quantified the similarity of oral kinematics between feeding and climbing in S. stimpsoni, evaluating the potential for either to represent an exaptation from the other. Premaxillary movements showed the greatest differences between scraping and suction feeding taxa. Between feeding and climbing, overall profiles of oral kinematics matched closely for most variables in S. stimpsoni, with only a few showing significant differences in maximum values. Although current data cannot resolve whether oral movements for climbing were coopted from feeding, or feeding movements coopted from climbing, similarities between feeding and climbing kinematics in S. stimpsoni are consistent with evidence of exaptation, with modifications, between these behaviors

  19. Dislocational Rock Mechanisms As a Basis for Seismic Methods in the Search for Hydrocarbons La géomécanique de dislocation en tant que base des méthodes sismiques de la recherche des hydrocarbures

    Directory of Open Access Journals (Sweden)

    Pissetski V. B.

    2006-11-01

    Full Text Available The analysis of the geological and geophysical data points out the inadequacy of the classical concept of a stratified continuous sedimentary medium on one hand. In the second hand it helps to introduce a serie of key physical concepts. The general formulation of the proposed concept can be presented as follows :(a The discrete character clearly observed during the sedimentation process ensures that changes of sedimentary cycles (hiatuses are marked by fine layers or surfaces which correspond to regular structures of strength defects later. (b The changes in gravity or tectonic load induce a destruction mechanism which regular growth changes a stratified continuous medium with defects into a dicrete medium. This destruction mechanism is a final process : each discrete element is limited in space by horizontal and vertical surfaces of disruption (dislocations. The final medium is a critical piling of elements which reacts easily to any change of the mechanical stress field. From this point of view, if we analyse outcrops and well data one notices a strong correspondance between the actual cracks and the main sedimentary limits. The main feature of the destruction mechanism is well reproduced in the laboratory by physical models built layer by layer with cristallisation pauses between layers. The theoretical analysis of the stress field of discrete media shows the predominance of vertical displacements and consequently the block aspect of the stress distribution within a compensation scheme. Thus, the key element in such a discrete medium model is the dislocation structure and the associated stress or pressure distribution. It becomes obvious that the main parameters of the fluid behaviour are determined by the density of dislocations and the value of the general pressure over the volume of the formation. The general pressure is defined as the sum of geostatic pressure and the anornafic pressure linked to the characteristic variability of the

  20. Convoluted dislocation loops induced by helium irradiation in reduced-activation martensitic steel and their impact on mechanical properties

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Fengfeng [Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Hubei Nuclear Solid Physics Key Laboratory, School of Physics and Technology, Wuhan University, Wuhan 430072 (China); Yao, Z. [Department of Mechanical and Materials Engineering, Queen' s University, Kingston, ON, Canada K7L 3N6 (Canada); Guo, Liping, E-mail: guolp@whu.edu.cn [Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Hubei Nuclear Solid Physics Key Laboratory, School of Physics and Technology, Wuhan University, Wuhan 430072 (China); Suo, Jinping [State Key Laboratory of Mould Technology, Institute of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China); Wen, Yongming [Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Hubei Nuclear Solid Physics Key Laboratory, School of Physics and Technology, Wuhan University, Wuhan 430072 (China)

    2014-06-01

    Helium irradiation induced dislocation loops in reduced-activation martensitic steels were investigated using transmission electron microscopy. The specimens were irradiated with 100 keV helium ions to 0.8 dpa at 350 °C. Unexpectedly, very large dislocation loops were found, significantly larger than that induced by other types of irradiations under the same dose. Moreover, the large loops were convoluted and formed interesting flower-like shape. The large loops were determined as interstitial type. Loops with the Burgers vectors of b=〈100〉 were only observed. Furthermore, irradiation induced hardening caused by these large loops was observed using the nano-indentation technique.

  1. Creep mechanisms of U720Li disc superalloy at intermediate temperature

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, Y., E-mail: yuan.yong@nims.go.jp [High Temperature Materials Center, National Institute for Materials Science, 1-2-1 Sengen, Ibaraki 305-0047 (Japan); Gu, Y.F.; Cui, C.Y.; Osada, T.; Tetsui, T.; Yokokawa, T.; Harada, H. [High Temperature Materials Center, National Institute for Materials Science, 1-2-1 Sengen, Ibaraki 305-0047 (Japan)

    2011-06-15

    Highlights: {yields} Crept microstructures of U720Li at 725 deg. C/630 MPa have been investigated by TEM. {yields} Orowan looping process combining dislocation slip and climb and partial dislocations shearing precipitates were the main creep mechanisms. {yields} Grain boundary sliding occurred at last creep stage. {yields} Three methods were suggested to improve the creep property at relatively high temperature. - Abstract: The microstructures of U720Li disc superalloy have been investigated by transmission electron microscopy (TEM) before and after creep test at 725 deg. C/630 MPa. The evolution of the crept microstructures was marked as three different stages (I, II and III) corresponding to gradually increased strain 0.1%, 5% and 27%, respectively. At stage I, dislocations bypassed secondary {gamma}' via Orowan loops. At stage II, partial dislocations started to shear secondary {gamma}', leaving stacking fault (SF) behind and microtwins formed in part of grains. At stage III, grain boundary sliding occurred due to very large strain and increased effective stress. The results indicated that the creep mechanisms of U720Li at 725 deg. C/630 MPa evolved with gradually increased strain. Orowan looping process combining dislocation slip and climb and partial dislocations shearing precipitates were the main creep mechanisms. It is suggested that decreasing the interparticle spacing of secondary {gamma}', strengthening secondary {gamma}' and decreasing stacking fault energy (SFE) of {gamma} matrix may be effective methods to improve the creep property at relatively higher temperatures.

  2. Creep mechanisms of U720Li disc superalloy at intermediate temperature

    International Nuclear Information System (INIS)

    Yuan, Y.; Gu, Y.F.; Cui, C.Y.; Osada, T.; Tetsui, T.; Yokokawa, T.; Harada, H.

    2011-01-01

    Highlights: → Crept microstructures of U720Li at 725 deg. C/630 MPa have been investigated by TEM. → Orowan looping process combining dislocation slip and climb and partial dislocations shearing precipitates were the main creep mechanisms. → Grain boundary sliding occurred at last creep stage. → Three methods were suggested to improve the creep property at relatively high temperature. - Abstract: The microstructures of U720Li disc superalloy have been investigated by transmission electron microscopy (TEM) before and after creep test at 725 deg. C/630 MPa. The evolution of the crept microstructures was marked as three different stages (I, II and III) corresponding to gradually increased strain 0.1%, 5% and 27%, respectively. At stage I, dislocations bypassed secondary γ' via Orowan loops. At stage II, partial dislocations started to shear secondary γ', leaving stacking fault (SF) behind and microtwins formed in part of grains. At stage III, grain boundary sliding occurred due to very large strain and increased effective stress. The results indicated that the creep mechanisms of U720Li at 725 deg. C/630 MPa evolved with gradually increased strain. Orowan looping process combining dislocation slip and climb and partial dislocations shearing precipitates were the main creep mechanisms. It is suggested that decreasing the interparticle spacing of secondary γ', strengthening secondary γ' and decreasing stacking fault energy (SFE) of γ matrix may be effective methods to improve the creep property at relatively higher temperatures.

  3. Climbing Walls and Climbing Tuitions. A Delta Perspective

    Science.gov (United States)

    Kirshstein, Rita J.; Kadamus, James A.

    2012-01-01

    High-end amenities like rock climbing walls on college campuses have become an easy target for those attempting to explain rising tuitions. This Delta Perspective looks beyond the media attention surrounding these "frills" to examine more serious questions about spending on campus facilities, college spending in general, and the real drivers of…

  4. Theory of interacting dislocations on cylinders.

    Science.gov (United States)

    Amir, Ariel; Paulose, Jayson; Nelson, David R

    2013-04-01

    We study the mechanics and statistical physics of dislocations interacting on cylinders, motivated by the elongation of rod-shaped bacterial cell walls and cylindrical assemblies of colloidal particles subject to external stresses. The interaction energy and forces between dislocations are solved analytically, and analyzed asymptotically. The results of continuum elastic theory agree well with numerical simulations on finite lattices even for relatively small systems. Isolated dislocations on a cylinder act like grain boundaries. With colloidal crystals in mind, we show that saddle points are created by a Peach-Koehler force on the dislocations in the circumferential direction, causing dislocation pairs to unbind. The thermal nucleation rate of dislocation unbinding is calculated, for an arbitrary mobility tensor and external stress, including the case of a twist-induced Peach-Koehler force along the cylinder axis. Surprisingly rich phenomena arise for dislocations on cylinders, despite their vanishing Gaussian curvature.

  5. Movement phase detection in climbing*

    NARCIS (Netherlands)

    Dovgalecs, Vladislavs; Boulanger, Jérémie; Orth, Dominic; Hérault, Romain; Coeurjolly, Jean François; Davids, Keith; Seifert, Ludovic

    2014-01-01

    The aim of this study was to propose a method to automatically detect the different types of behavioural states in climbing. One climber traversed an easy route (5c difficulty on French scale) of 10 m height with a top-rope. Five inertial measurement units (IMU) (3D accelerometer, 3D gyroscope, 3D

  6. Hill climbing algorithms and trivium

    DEFF Research Database (Denmark)

    Borghoff, Julia; Knudsen, Lars Ramkilde; Matusiewicz, Krystian

    2011-01-01

    This paper proposes a new method to solve certain classes of systems of multivariate equations over the binary field and its cryptanalytical applications. We show how heuristic optimization methods such as hill climbing algorithms can be relevant to solving systems of multivariate equations...

  7. Hill-climbing Higgs inflation

    Science.gov (United States)

    Jinno, Ryusuke; Kaneta, Kunio; Oda, Kin-ya

    2018-01-01

    We propose a realization of cosmic inflation with the Higgs field when the Higgs potential has degenerate vacua by employing the recently proposed idea of hill-climbing inflation. The resultant inflationary predictions exhibit a sizable deviation from those of the ordinary Higgs inflation.

  8. Climbing fiber signaling and cerebellar gain control

    NARCIS (Netherlands)

    G. Ohtsuki (Gen); C. Piochon (Claire); C.R.W. Hansel (Christian)

    2009-01-01

    textabstractThe physiology of climbing fiber signals in cerebellar Purkinje cells has been studied since the early days of electrophysiology. Both the climbing fiber-evoked complex spike and the role of climbing fiber activity in the induction of long-term depression (LTD) at parallel fiber-Purkinje

  9. A Survey of Wall Climbing Robots: Recent Advances and Challenges

    Directory of Open Access Journals (Sweden)

    Shunsuke Nansai

    2016-07-01

    Full Text Available In recent decades, skyscrapers, as represented by the Burj Khalifa in Dubai and Shanghai Tower in Shanghai, have been built due to the improvements of construction technologies. Even in such newfangled skyscrapers, the façades are generally cleaned by humans. Wall climbing robots, which are capable of climbing up vertical surfaces, ceilings and roofs, are expected to replace the manual workforce in façade cleaning works, which is both hazardous and laborious work. Such tasks require these robotic platforms to possess high levels of adaptability and flexibility. This paper presents a detailed review of wall climbing robots categorizing them into six distinct classes based on the adhesive mechanism that they use. This paper concludes by expanding beyond adhesive mechanisms by discussing a set of desirable design attributes of an ideal glass façade cleaning robot towards facilitating targeted future research with clear technical goals and well-defined design trade-off boundaries.

  10. Atraumatic Anterior Dislocation of the Hip Joint

    Directory of Open Access Journals (Sweden)

    Tadahiko Ohtsuru

    2015-01-01

    Full Text Available Dislocation of the hip joint in adults is usually caused by high-energy trauma such as road traffic accidents or falls from heights. Posterior dislocation is observed in most cases. However, atraumatic anterior dislocation of the hip joint is extremely rare. We present a case of atraumatic anterior dislocation of the hip joint that was induced by an activity of daily living. The possible causes of this dislocation were anterior capsule insufficiency due to developmental dysplasia of the hip, posterior pelvic tilt following thoracolumbar kyphosis due to vertebral fracture, and acetabular anterior coverage changes by postural factor. Acetabular anterior coverage changes in the sagittal plane were measured using a tomosynthesis imaging system. This system was useful for elucidation of the dislocation mechanism in the present case.

  11. Canonical Quantization of Crystal Dislocation and Electron-Dislocation Scattering in an Isotropic Media

    Science.gov (United States)

    Li, Mingda; Cui, Wenping; Dresselhaus, M. S.; Chen, Gang; MIT Team; Boston College Team

    Crystal dislocations govern the plastic mechanical properties of materials but also affect the electrical and optical properties. However, a fundamental and decent quantum-mechanical theory of dislocation remains undiscovered for decades. Here we present an exact and manageable Hamiltonian theory for both edge and screw dislocation line in an isotropic media, where the effective Hamiltonian of a single dislocation line can be written in a harmonic-oscillator-like form, with closed-form quantized 1D phonon-like excitation. Moreover a closed-form, position dependent electron-dislocation coupling strength is obtained, from which we obtained good agreement of relaxation time when comparing with classical results. This Hamiltonian provides a platform to study the effect of dislocation to materials' non-mechanical properties from a fundamental Hamiltonian level.

  12. Estimation of dislocations density and distribution of dislocations during ECAP-Conform process

    Science.gov (United States)

    Derakhshan, Jaber Fakhimi; Parsa, Mohammad Habibi; Ayati, Vahid; Jafarian, Hamidreza

    2018-01-01

    Dislocation density of coarse grain aluminum AA1100 alloy (140 µm) that was severely deformed by Equal Channel Angular Pressing-Conform (ECAP-Conform) are studied at various stages of the process by electron backscattering diffraction (EBSD) method. The geometrically necessary dislocations (GNDs) density and statistically stored dislocations (SSDs) densities were estimate. Then the total dislocations densities are calculated and the dislocation distributions are presented as the contour maps. Estimated average dislocations density for annealed of about 2×1012 m-2 increases to 4×1013 m-2 at the middle of the groove (135° from the entrance), and they reach to 6.4×1013 m-2 at the end of groove just before ECAP region. Calculated average dislocations density for one pass severely deformed Al sample reached to 6.2×1014 m-2. At micrometer scale the behavior of metals especially mechanical properties largely depend on the dislocation density and dislocation distribution. So, yield stresses at different conditions were estimated based on the calculated dislocation densities. Then estimated yield stresses were compared with experimental results and good agreements were found. Although grain size of material did not clearly change, yield stress shown intensive increase due to the development of cell structure. A considerable increase in dislocations density in this process is a good justification for forming subgrains and cell structures during process which it can be reason of increasing in yield stress.

  13. Dislocation morphology in deformed and irradiated niobium

    International Nuclear Information System (INIS)

    Chang, C.P.

    1977-06-01

    Niobium foils of moderate purity were examined for the morphology of dislocations or defect clusters in the deformed or neutron-irradiated state by transmission electron microscopy. New evidence has been found for the dissociation of screw dislocations into partials on the (211) slip plane according to the Crussard mechanism: (a/2) [111] → (a/3) [111] + (a/6) [111

  14. Diagnosis of climbing related overuse injuries

    International Nuclear Information System (INIS)

    Klauser, A.; Frauscher, F.; Helweg, G.; Nedden, D. zur; Hochholzer, T.; Kramer, J.

    2002-01-01

    Sport climbing shows an enormous increase in participation, evolving to more popularity, including even school sport activity on high standards. Therefore the number of climbing related injuries is increasing and becomes a more frequently encountered medical problem. Typical climbing associated injuries involve predominantly the upper limb. Overuse injuries are the most common climbing related injuries.The clinical examination is the first line investigation, which is often limited especially in the acute phase. However, an exact diagnosis is desireable for therapeutic management. Imaging modalities have shown to be capable for detection of climbing related injuries. An overview about the current use of x-ray, ultrasound and magnetic resonance imaging in different climbing related overuse injuries is presented. (orig.) [de

  15. Study of elementary mechanisms of creep in uranium as a function of temperature (150 deg. to 760 deg. C) by activation energy measurements

    International Nuclear Information System (INIS)

    Grenier, P.

    1966-06-01

    Creep tests were carried out on single crystals and polycrystalline specimens of uranium in both the α and β phases over the temperature range 150 - 760 deg. C. The determination of the activation energy for creep and the study of its variation with temperature made it possible to distinguish various temperature ranges in which one or more elementary mechanisms govern deformation. Micrographic observations after creep and the study of the variation of creep-rate with load support the conclusions. The creep behavior of single crystals is identical with that of polycrystalline material below 325 deg. C. From 325 deg. C to one upper limiting temperature whose value depends on the purity and previous history of the metal, the creep deformation of uranium is controlled by cross-slip. From this limiting temperature up to 520 deg. C, the creep of uranium involves two independent mechanisms operating simultaneously, the movement of screw dislocation by cross-slip and the climbing of edge dislocations out of their slip plane. Between 520 deg. C and the α - β transformation temperature creep in polycrystals is governed by the climb of edge dislocations out of their slip planes, by a pile up mechanism in the case of primary creep and by dipole annihilation in the case of secondary creep. In single crystals creep is dependent on the climb of edge dislocations into pre-existent sub-boundaries and their subsequent rearrangement within these boundaries. In the β phase the creep of polycrystals is governed by the diffusional climb of edge dislocations. Between 450 and 630 deg. C small alloy additions of molybdenum modify the creep characteristics of uranium although the deformation mechanisms involved are analogous to those in the pure metal. (author) [fr

  16. Climbing Fiber Signaling and Cerebellar Gain Control

    Science.gov (United States)

    Ohtsuki, Gen; Piochon, Claire; Hansel, Christian

    2009-01-01

    The physiology of climbing fiber signals in cerebellar Purkinje cells has been studied since the early days of electrophysiology. Both the climbing fiber-evoked complex spike and the role of climbing fiber activity in the induction of long-term depression (LTD) at parallel fiber-Purkinje cell synapses have become hallmark features of cerebellar physiology. However, the key role of climbing fiber signaling in cerebellar motor learning has been challenged by recent reports of forms of synaptic and non-synaptic plasticity in the cerebellar cortex that do not involve climbing fiber activity, but might well play a role in cerebellar learning. Moreover, cerebellar LTD does not seem to strictly require climbing fiber activity. These observations make it necessary to re-evaluate the role of climbing fiber signaling in cerebellar function. Here, we argue that climbing fiber signaling is about adjusting relative probabilities for the induction of LTD and long-term potentiation (LTP) at parallel fiber synapses. Complex spike-associated, dendritic calcium transients control postsynaptic LTD and LTP induction. High calcium transients, provided by complex spike activity, do not only favor postsynaptic LTD induction, but simultaneously trigger retrograde cannabinoid signaling, which blocks the induction of presynaptic LTP. Plasticity of the climbing fiber input itself provides additional means to fine-tune complex spike associated calcium signaling and thus to adjust the gain of heterosynaptic climbing fiber control. In addition to dendritic calcium transients, climbing fiber activity leads to the release of the neuropeptide corticotropin-releasing factor (CRF), which facilitates LTD induction at both parallel fiber and climbing fiber synapses. PMID:19597563

  17. Climbing fiber signaling and cerebellar gain control

    Directory of Open Access Journals (Sweden)

    Gen Ohtsuki

    2009-07-01

    Full Text Available The physiology of climbing fiber signals in cerebellar Purkinje cells has been studied since the early days of electrophysiology. Both the climbing fiber-evoked complex spike and the role of climbing fiber activity in the induction of long-term depression (LTD at parallel fiber-Purkinje cell synapses have become hallmark features of cerebellar physiology. However, the key role of climbing fiber signaling in cerebellar motor learning has been challenged by recent reports of forms of synaptic and non-synaptic plasticity in the cerebellar cortex that do not involve climbing fiber activity, but might well play a role in cerebellar learning. Moreover, cerebellar LTD does not seem to strictly require climbing fiber activity. These observations make it necessary to re-evaluate the role of climbing fiber signaling in cerebellar function. Here, we argue that climbing fiber signaling is about adjusting relative probabilities for the induction of LTD and long-term potentiation (LTP at parallel fiber synapses. Complex spike-associated, dendritic calcium transients control postsynaptic LTD and LTP induction. High calcium transients, provided by complex spike activity, do not only favor postsynaptic LTD induction, but simultaneously trigger retrograde cannabinoid signaling, which blocks the induction of presynaptic LTP. Plasticity of the climbing fiber input itself provides additional means to fine-tune complex spike associated calcium signaling and thus to adjust the gain of heterosynaptic climbing fiber control. In addition to dendritic calcium transients, climbing fiber activity leads to the release of the neuropeptide corticotropin-releasing factor (CRF, which facilitates LTD induction at both parallel fiber and climbing fiber synapses.

  18. Clinical Treatment of Chronic Condylar Dislocation by Restoring Anterior Guidance

    OpenAIRE

    澤田, 宏二; 荒井, 良明; メディナ, ラウル; 河野, 正司; 福井, 忠雄; 花田, 晃治; Sawada, Koji; Arai, Yoshiaki; Medina, Raul; Kohno, Shoji; Fukui, Tadao; Hanada, Kooji

    1997-01-01

    The mechanism of condylar dislocation is not exactly understood. Temporomandibular (TMJ) surgery is a common option in the treatment of chronic condylar dislocation, but some authors have reported disappearance of its symptomatology after occlusal treatment. A case in which condylar dislocation disappeared by changing the location of anterior guidance is presented. The patient was an 18 year-old male with an Angle class Ⅲ malocclusion who had been suffering from condylar dislocation of the ri...

  19. 14 CFR 31.17 - Performance: Climb.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Performance: Climb. 31.17 Section 31.17 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: MANNED FREE BALLOONS Flight Requirements § 31.17 Performance: Climb. (a) Each balloon must be...

  20. The gauge theory of dislocations: A nonuniformly moving screw dislocation

    Energy Technology Data Exchange (ETDEWEB)

    Lazar, Markus, E-mail: lazar@fkp.tu-darmstadt.d [Emmy Noether Research Group, Department of Physics, Darmstadt University of Technology, Hochschulstr. 6, D-64289 Darmstadt (Germany); Department of Physics, Michigan Technological University, Houghton, MI 49931 (United States)

    2010-07-05

    We investigate the nonuniform motion of a straight screw dislocation in infinite media in the framework of the translational gauge theory of dislocations. The equations of motion are derived for an arbitrarily moving screw dislocation. The fields of the elastic velocity, elastic distortion, dislocation density and dislocation current surrounding the arbitrarily moving screw dislocation are derived explicitly in the form of integral representations. We calculate the radiation fields and the fields depending on the dislocation velocities.

  1. Step climbing omnidirectional mobile robot with passive linkages

    Science.gov (United States)

    Chugo, Daisuke; Kawabata, Kuniaki; Kaetsu, Hayato; Asama, Hajime; Mishima, Taketoshi

    2005-12-01

    In this paper, we develop a holonomic omni-directional mobile vehicle with step-climbing ability. This system realizes omni-directional motion on flat floor using special wheels and passes over the step in forward or backward direction using the passive linkage mechanism. Our key ideas are the following topics. First topic is new omnidirectional mobile mechanism which consists of special wheels and passive linkage mechanism. Second topic is new passive linkage mechanism which can change its body configuration easily when the vehicle passes over the step. Third topic is wheel control reference derivation based on the body configuration, which changes passively during step climbing for reducing wheel slippage. Last topic is wheel control method which keeps the rotation velocity coordination among the wheels for reducing wheel slippage and increasing the step-climbing performance. We verified the effectiveness of our proposed method by the computer simulations and experiments. Utilizing our proposed mechanism and control systems, the vehicle has both omnidirectional mobility and step overcoming function. Furthermore, our developing vehicle can pass over the 128[mm] height step using the wheel which radius is 66[mm]. Its performance is three times larger than one of general wheeled vehicle.

  2. Irreducible Galeazzi Fracture-Dislocations.

    Science.gov (United States)

    Yohe, Nicholas J; De Tolla, Jadie; Kaye, Marc B; Edelstein, David M; Choueka, Jack

    2017-11-01

    Fractures of the radial shaft with disruption of the distal radial ulnar joint (DRUJ) or Galeazzi fractures are treated with reduction of the radius followed by stability assessment of the DRUJ. In rare instances, the reduction of the DRUJ is blocked by interposed structures requiring open reduction of this joint. The purpose of this study is to review all cases of irreducible Galeazzi fracture-dislocations reported in the literature to offer guidelines in the diagnosis and management of this rare injury. A search of the MEDLINE database, OVID database, and PubMed database was employed using the terms "Galeazzi" and "fracture." Of the 124 articles the search produced, a total of 12 articles and 17 cases of irreducible Galeazzi fracture-dislocations were found. The age range was 16 to 64 years (mean = 25 years). A high-energy mechanism of injury was the root cause in all cases. More than half of the irreducible DRUJ dislocations were not identified intraoperatively. In a dorsally dislocated DRUJ, a block to reduction in most cases (92.3%) was secondary to entrapment of one or more extensor tendons including the extensor carpi ulnaris, extensor digiti minimi, and extensor digitorum communis, with the remaining cases blocked by fracture fragments. Irreducible volar dislocations due to entrapment of the ulnar head occurred in 17.6% of cases with no tendon entrapment noted. In the presence of a Galeazzi fracture, a reduced/stable DRUJ needs to be critically assessed as more than half of irreducible DRUJs in a Galeazzi fracture-dislocation were missed either pre- or intraoperatively.

  3. Anterior shoulder dislocations in sports.

    Science.gov (United States)

    Aronen, J G

    1986-01-01

    Anterior shoulder dislocations, primary and recurrent, are among the most disabling injuries to the shoulder that can plague the athlete. The diagnosis is easily made by the following: the physical appearance of the shoulder; loss of capability by the athlete to internally and externally rotate the shoulder with the elbow at his side; by evaluating the mechanism of injury; and x-rays. Anterior shoulder dislocations should be reduced as soon as possible after diagnosis, to minimise the stretching effect on the neurovascular structures while the humeral head is dislocated. The reduction is not done to allow the athlete to return immediately to sport. Use of a simple traction method in the first 10 to 15 minutes following the injury will result in a successful reduction in the vast majority of dislocations. Reduction of the humeral head can be confirmed by the athlete regaining the capability to internally and externally rotate his shoulder with his elbow at his side. Following reduction, the athlete should begin a treatment regimen which includes a restrengthening programme emphasising the muscles of internal rotation and adduction plus rigid restrictions of activities until the goals of the rehabilitation programme are satisfied. The author's experience with this treatment regimen with athletes at the United States Naval Academy, has shown a decrease of the recurrence rate of primary anterior shoulder dislocations to 25% versus the 80% recurrence rate we have become familiar with from studies done which did not stress specific rehabilitation programmes. The athlete should also be instructed in a self-performed traction method for reduction should a redislocation occur, to minimise the stretching effect on the neurovascular structures and allow relief from discomfort. Surgery for primary and recurrent anterior dislocations should only be considered when the athlete fails to achieve the desired goals after participating in a specific, progressive, adequate

  4. Irradiation creep induced anisotropy in a/2 dislocation populations

    International Nuclear Information System (INIS)

    Gelles, D.S.

    1984-05-01

    The contribution of anisotropy in Burgers vector distribution to irradiation creep behavior has been largely ignored in irradiation creep models. However, findings on Frank loops suggest that it may be very important. Procedures are defined to identify the orientations of a/2 Burgers vectors for dislocations in face-centered cubic crystals. By means of these procedures the anisotropy in Burgers vector populations was determined for three Nimonic PE16 pressurized tube specimens irradiated under stress. Considerable anisotropy in Burgers vector population develops during irradiation creep. It is inferred that dislocation motion during irradiation creep is restricted primarily to a climb of a/2 dislocations on 100 planes. Effect of these results on irradiation creep modeling and deformation induced irradiation growth is considered

  5. Megachiropteran bats profoundly unique from microchiropterans in climbing and walking locomotion: Evolutionary implications.

    Directory of Open Access Journals (Sweden)

    Rick A Adams

    Full Text Available Understandably, most locomotor analyses of bats have focused on flight mechanics and behaviors. However, we investigated nonflight locomotion in an effort to glean deeper insights into the evolutionary history of bats. We used high-speed video (300 Hz to film and compare walking and climbing mechanics and kinematics between several species of the suborders Megachiroptera (Pteropodidae versus Microchiroptera (Vespertilionidae and Phyllostomatidae. We found fundamentally distinctive behaviors, functional abilities, and performance outcomes between groups, but nearly homogeneous outcomes within groups. Megachiropterans exhibited climbing techniques and skills not found in microchiropterans and which aligned with other fully arboreal mammals. Megachiropterans climbed readily when placed in a head-up posture on a vertical surface, showed significantly greater ability than microchiropterans to abduct and extend the reach of their limbs, and climbed at a greater pace by using a more aggressive ipsilateral gait, at times being supported by only a single contact point. In addition, megachiropterans showed little ability to employ basic walking mechanics when placed on the ground, also a pattern observed in some highly adapted arboreal mammals. Conversely, microchiropterans resisted climbing vertical surfaces in a head-up posture, showed significantly less extension of their limbs, and employed a less-aggressive, slower contralateral gait with three points of contact. When walking, microchiropterans used the same gait they did when climbing which is representative of basic tetrapod terrestrial mechanics. Curiously, megachiropterans cycled their limbs significantly faster when climbing than when attempting to walk, whereas microchiropterans cycled their limbs at significantly faster rates when walking than when climbing. We contend that nonflight locomotion mechanics give a deep evolutionary view into the ancestral es locomotor platform on which flight was

  6. Primary traumatic patellar dislocation

    Directory of Open Access Journals (Sweden)

    Tsai Chun-Hao

    2012-06-01

    Full Text Available Abstract Acute traumatic patellar dislocation is a common injury in the active and young adult populations. MRI of the knee is recommended in all patients who present with acute patellar dislocation. Numerous operative and non-operative methods have been described to treat the injuries; however, the ideal management of the acute traumatic patellar dislocation in young adults is still in debate. This article is intended to review the studies to the subjects of epidemiology, initial examination and management.

  7. Kneecap dislocation - aftercare

    Science.gov (United States)

    Patellar subluxation - aftercare; Patellofemoral subluxation - aftercare; Kneecap subluxation - aftercare ... is twisting motion or a sudden turn. Kneecap subluxation or dislocation may occur more than once. The ...

  8. Hill-Climbing Attacks and Robust Online Signature Verification Algorithm against Hill-Climbing Attacks

    Science.gov (United States)

    Muramatsu, Daigo

    Attacks using hill-climbing methods have been reported as a vulnerability of biometric authentication systems. In this paper, we propose a robust online signature verification algorithm against such attacks. Specifically, the attack considered in this paper is a hill-climbing forged data attack. Artificial forgeries are generated offline by using the hill-climbing method, and the forgeries are input to a target system to be attacked. In this paper, we analyze the menace of hill-climbing forged data attacks using six types of hill-climbing forged data and propose a robust algorithm by incorporating the hill-climbing method into an online signature verification algorithm. Experiments to evaluate the proposed system were performed using a public online signature database. The proposed algorithm showed improved performance against this kind of attack.

  9. Thermodynamic theory of dislocation-enabled plasticity

    Science.gov (United States)

    Langer, J. S.

    2017-11-01

    The thermodynamic theory of dislocation-enabled plasticity is based on two unconventional hypotheses. The first of these is that a system of dislocations, driven by external forces and irreversibly exchanging heat with its environment, must be characterized by a thermodynamically defined effective temperature that is not the same as the ordinary temperature. The second hypothesis is that the overwhelmingly dominant mechanism controlling plastic deformation is thermally activated depinning of entangled pairs of dislocations. This paper consists of a systematic reformulation of this theory followed by examples of its use in analyses of experimentally observed phenomena including strain hardening, grain-size (Hall-Petch) effects, yielding transitions, and adiabatic shear banding.

  10. Control of a stair climbing wheelchair

    Directory of Open Access Journals (Sweden)

    Nor Maniha Abdul Ghani

    2012-08-01

    Full Text Available This paper presents investigations into the control of a stair climbing wheelchair particularly for indoor usage. A virtual wheelchair model is developed using Visual Nastran software and linked with Matlab/Simulink for control purposes. The goals are to have a simple, compact and stable stairs climbing wheelchair in order to complete the ascending and descending tasks. The challenges are to ensure the wheelchair seat always stay at the upright position and to control both the front and rear wheel motors while climbing. PID control is used to provide appropriate torque to both front and rear wheels as well as at to the wheelchair seat during climbing. Results show that the wheelchair movement can be controlled smoothly and the seat maintained at the desired position with the adapted approach.

  11. Ultrasonic Study of Dislocation Dynamics in Lithium -

    Science.gov (United States)

    Han, Myeong-Deok

    1987-09-01

    Experimental studies of dislocation dynamics in LiF single crystals, using ultrasonic techniques combined with dynamic loading, were performed to investigate the time evolution of the plastic deformation process under a short stress pulse at room temperature, and the temperature dependence of the dislocation damping mechanism in the temperature range 25 - 300(DEGREES)K. From the former, the time dependence of the ultrasonic attenuation was understood as resulting from dislocation multiplication followed by the evolution of mobile dislocations to immobile ones under large stress. From the latter, the temperature dependence of the ultrasonic attenuation was interpreted as due to the motion of the dislocation loops overcoming the periodic Peierls potential barrier in a manner analogous to the motion of a thermalized sine-Gordon chain under a small stress. The Peierls stress obtained from the experimental results by application of Seeger's relaxation model with exponential dislocation length distribution was 4.26MPa, which is consistent with the lowest stress for the linear relation between the dislocation velocity and stress observed by Flinn and Tinder.

  12. Interaction of 〈1 0 0〉 dislocation loops with dislocations studied by dislocation dynamics in α-iron

    Energy Technology Data Exchange (ETDEWEB)

    Shi, X.J.; Dupuy, L. [CEA, DEN, SRMA, F-91191 Gif-sur-Yvette (France); Devincre, B. [Laboratoire d’Etude des Microstructures, CNRS-ONERA, 29 av. de la Division Leclerc, 92322 Châtillon Cedex (France); Terentyev, D. [SCK–CEN, Nuclear Materials Science Institute, Boeretang 200, B-2400 Mol (Belgium); Vincent, L. [CEA, DEN, SRMA, F-91191 Gif-sur-Yvette (France)

    2015-05-15

    Highlights: • Interactions between edge dislocations and radiation-induced loops were studied by dislocation dynamics. • Dislocation dynamics results are directly compared to molecular dynamics results. • The complex elementary reactions are successfully reproduced. • The critical shear stress to overcome individual loops if reproduced quantitatively. - Abstract: Interstitial dislocation loops with Burgers vector of 〈1 0 0〉 type are formed in α-iron under neutron or heavy ion irradiation. As the density and size of these loops increase with radiation dose and temperature, these defects are thought to play a key role in hardening and subsequent embrittlement of iron-based steels. The aim of the present work is to study the pinning strength of the loops on mobile dislocations. Prior to run massive Dislocation Dynamics (DD) simulations involving experimentally representative array of radiation defects and dislocations, the DD code and its parameterization are validated by comparing the individual loop–dislocation reactions with those obtained from direct atomistic Molecular Dynamics (MD) simulations. Several loop–dislocation reaction mechanisms are successfully reproduced as well as the values of the unpinning stress to detach mobile dislocations from the defects.

  13. Dislocation microstructure evolution in cyclically twisted microsamples: a discrete dislocation dynamics simulation

    International Nuclear Information System (INIS)

    Senger, J; Weygand, D; Kraft, O; Gumbsch, P

    2011-01-01

    Miniaturization in technical devices has increased interest in the investigation of the deformation and fatigue behaviour of metals in the micrometre regime. Due to the small dimensions of these devices, mechanical properties depend on the motion of a marginal number of dislocations. In this paper, the evolution of dislocation microstructure in torsion loaded single crystalline aluminium wires is analysed by three-dimensional discrete dislocation dynamics simulations. It is shown that the size of pile-ups and the number of the active slip systems is significantly influenced by cross-slip events independent of the crystallographic orientation. Dislocations are driven by the stress gradient from the applied loading to move into the centre of the sample. These dislocations cannot escape through the surface because of the reversal of the sign of the stress in the centre of the sample. If the micrometre-sized specimens are untwisted, the remaining dislocation microstructure in these samples depends on the maximum torsion angle reached before unloading. The larger the torsion angle, the higher is the remaining dislocation density in the unloaded specimens. These results are discussed with respect to cyclic deformation mechanisms at small scale

  14. Promoting Atomic Scale Engineering by Quantifying Experimental Observations of Dislocation Cores

    National Research Council Canada - National Science Library

    Hemker, Kevin

    1998-01-01

    ... to their dislocation structures. The research support by this grant, and described here, was undertaken to elucidate the relationship between atomic level dislocation core structures, alloy composition, and macroscopic mechanical...

  15. Fabrication of mesoscopic floating Si wires by introducing dislocations

    International Nuclear Information System (INIS)

    Motohashi, Mitsuya; Shimizu, Kazuya; Niwa, Masaaki; Suzuki, Toshiaki

    2014-01-01

    We fabricated a mesoscopic Si wire by introducing dislocations in a silicon wafer before HF anodization. The dislocations formed along the (111) crystal plane. The outline of the dislocation line was an inverted triangle. The resulting wire floated on a bridge girder and had a hybrid structure consisting of a porous layer and crystalline Si. The cross section of the wire had an inverted triangle shape. The wire formation mechanism is discussed in terms of carrier transport, crystal structure, and dislocation formation during anodization. (paper)

  16. Fabrication of mesoscopic floating Si wires by introducing dislocations

    Science.gov (United States)

    Motohashi, Mitsuya; Shimizu, Kazuya; Suzuki, Toshiaki; Niwa, Masaaki

    2014-12-01

    We fabricated a mesoscopic Si wire by introducing dislocations in a silicon wafer before HF anodization. The dislocations formed along the (111) crystal plane. The outline of the dislocation line was an inverted triangle. The resulting wire floated on a bridge girder and had a hybrid structure consisting of a porous layer and crystalline Si. The cross section of the wire had an inverted triangle shape. The wire formation mechanism is discussed in terms of carrier transport, crystal structure, and dislocation formation during anodization.

  17. Climbing plants: attachment adaptations and bioinspired innovations.

    Science.gov (United States)

    Burris, Jason N; Lenaghan, Scott C; Stewart, C Neal

    2018-04-01

    Climbing plants have unique adaptations to enable them to compete for sunlight, for which they invest minimal resources for vertical growth. Indeed, their stems bear relatively little weight, as they traverse their host substrates skyward. Climbers possess high tensile strength and flexibility, which allows them to utilize natural and manmade structures for support and growth. The climbing strategies of plants have intrigued scientists for centuries, yet our understanding about biochemical adaptations and their molecular undergirding is still in the early stages of research. Nonetheless, recent discoveries are promising, not only from a basic knowledge perspective, but also for bioinspired product development. Several adaptations, including nanoparticle and adhesive production will be reviewed, as well as practical translation of these adaptations to commercial applications. We will review the botanical literature on the modes of adaptation to climb, as well as specialized organs-and cellular innovations. Finally, recent molecular and biochemical data will be reviewed to assess the future needs and new directions for potential practical products that may be bioinspired by climbing plants.

  18. Growth and instability of charged dislocation loops under irradiation in ceramic materials

    CERN Document Server

    Ryazanov, A I; Kinoshita, C; Klaptsov, A V

    2002-01-01

    We have investigated the physical mechanisms of the growth and stability of charged dislocation loops in ceramic materials with very strong different mass of atoms (stabilized cubic zirconia) under different energies and types of irradiation conditions: 100-1000 keV electrons, 100 keV He sup + and 300 keV O sup + ions. The anomalous formation of extended defect clusters (charged dislocation loops) has been observed by TEM under electron irradiation subsequent to ion irradiation. It is demonstrated that very strong strain field (contrast) near charged dislocation loops is formed. The dislocation loops grow up to a critical size and after then become unstable. The instability of the charged dislocation loop leads to the multiplication of dislocation loops and the formation of dislocation network near the charged dislocation loops. A theoretical model is suggested for the explanation of the growth and stability of the charged dislocation loop, taking the charge state of point defects. The calculated distribution...

  19. The influence of anxiety on visual attention in climbing

    NARCIS (Netherlands)

    Nieuwenhuys, A.; Pijpers, J.R.; Oudejans, R.R.D.; Bakker, F.C.

    2008-01-01

    The object of the current study was to investigate anxiety-induced changes in movement and gaze behavior in novices on a climbing wall. Identical traverses were situated at high and low levels on a climbing wall to manipulate anxiety. In line with earlier studies, climbing times and movement times

  20. Physical Properties of Climbing Black Pepper ( Piper nigrum ) and ...

    African Journals Online (AJOL)

    Mass, density and moisture loss of climbing pepper were significantly affected by drying temperature and duration at 5% level of significance. Other climbing pepper physical properties under study were not influenced significantly. All alligator pepper properties considered were not significant (p > 0.05). Climbing pepper ...

  1. Design of a Docking Wall-Climbing Robot

    Directory of Open Access Journals (Sweden)

    Rong Liu

    2013-02-01

    Full Text Available This paper introduces an innovative wall-climbing robot. The robot consists of two single-body negative pressure adsorption robots which could dock together as a mother-robot or separate into two independent child-robots. The child-robots connect with each other through a docking mechanism which can not only lock solidly and unlock smoothly but which can also adjust the relative position of the two child-robots. This design guarantees that while in dock mode the mother robot will be able to cross some barriers which are impossible to surmount for a single-body wall-climbing robot, while in separate mode the child-robots maintain agility and mobility compared to other two-body robots. In this paper, an overview of the mechanical structure of the robot is first presented and then three possible mechanisms for barrier-crossing are discussed and a reasonable one is selected. An analysis of the initial docking condition of the selected design is also given which provides the basis for the experiments and research for the future.

  2. Appendicular joint dislocations.

    Science.gov (United States)

    Hindle, Paul; Davidson, Eleanor K; Biant, Leela C; Court-Brown, Charles M

    2013-08-01

    This study defines the incidence and epidemiology of joint dislocations and subluxations of the appendicular skeleton. All patients presenting acutely to hospital with a dislocation or subluxation of the appendicular skeleton from a defined population were included in the study. There were 974 dislocations or subluxations over one year between the 1st November 2008 and the 31st October 2009. There was an overall joint dislocation incidence of 157/10(5)/year (188/10(5)/year in males and 128/10(5)/year in females). Males demonstrated a bimodal distribution with a peak incidence of 446/10(5)/year at 15-24 years old and another of 349/10(5)/year in those over 90 years. Females demonstrate an increasing incidence from the seventh decade with a maximum incidence of 520/10(5)/year in those over 90 years. The most commonly affected joints are the glenohumeral (51.2/10(5)/year), the small joints of the hand (29.9/10(5)/year), the patellofemoral joint (21.6/10(5)/year), the prosthetic hip (19.0/10(5)/year), the ankle (11.5/10(5)/year), the acromioclavicular joint (8.9/10(5)/year) and the elbow (5.5/10(5)/year). Unlike fractures, dislocations are more common in the both the most affluent and the most socially deprived sections of the population. Joint disruptions are more common than previously estimated. Copyright © 2013 Elsevier Ltd. All rights reserved.

  3. A rough concrete wall-climbing robot based on grasping claws

    Directory of Open Access Journals (Sweden)

    Fengyu Xu

    2016-10-01

    Full Text Available Climbing robots have been widely used to inspect smooth walls. However, a good adsorption method has not been found for the inspection of a cliff surface and a dusty high-altitude surface with small vibration, both of which are made of coarse concrete, square brick, or rock. In this article, first, we analyzed the bionic structure of the cockroach legs and observed their morphological characteristics of the spiny claws on these legs. We also studied the interaction theory of the bionic claw with the bulges on the rough wall surfaces and deduced the mechanical criteria of the claws grabbing steadily these bulges. Then, an initial mechanical structure of a wall-climbing robot was proposed based on a grasping claw and a climbing model. Furthermore, a mathematical model was established to reflect the relationship between sharp hooks and bulges on the rough wall. Finally, we performed several laboratory experiments to verify the grasping stability.

  4. Modeling of dislocation generation and interaction during high-speed deformation of metals

    DEFF Research Database (Denmark)

    Schiøtz, J.; Leffers, T.; Singh, B.N.

    2002-01-01

    Recent experiments by Kiritani et al. [1] have revealed a surprisingly high rate of vacancy production during highspeed deformation of thin foils of fcc metals. Virtually no dislocations are seen after the deformation. This is interpreted as evidence for a dislocation-free deformation mechanism...... for the generation of vacancies are investigated. The main process is found to be incomplete annihilation of segments of edge dislocations on adjacent slip planes. The dislocations are also seen to be participating in complicated dislocation reactions, where sessile dislocation segments are constantly formed...

  5. Isolated dorsal dislocation of the tarsal naviculum

    Directory of Open Access Journals (Sweden)

    Kaziz Hamdi

    2015-01-01

    Full Text Available Isolated dislocation of the tarsal naviculum is an unusual injury, scarcely reported in the literature. The naviculum is surrounded by the rigid bony and ligamentous support hence fracture dislocation is more common than isolated dislocation. The mechanism and treatment options remain unclear. In this case report, we describe a 31 year old man who sustained an isolated dorsal dislocation of the left tarsal naviculum, without fracture, when he was involved in a motor vehicle collision. The reported mechanism of the dislocation is a hyper plantar flexion force applied to the midfoot, resulting in a transient disruption of the ligamentous support of the naviculum bone, with dorsal displacement of the bone. The patient was treated with open reduction and Krischner-wire fixation of the navicular after the failure of closed reduction. The wires were removed after 6 weeks postoperatively. Physiotherapy for stiffness and midfoot pain was recommended for 2 months. At 6 months postoperatively, limping, midfoot pain and weakness were reported, no X-ray abnormalities were found. The patient returned to his obvious activities with a normal range of motion.

  6. Isolated dorsal dislocation of the tarsal naviculum.

    Science.gov (United States)

    Hamdi, Kaziz; Hazem, Ben Ghozlen; Yadh, Zitoun; Faouzi, Abid

    2015-01-01

    Isolated dislocation of the tarsal naviculum is an unusual injury, scarcely reported in the literature. The naviculum is surrounded by the rigid bony and ligamentous support hence fracture dislocation is more common than isolated dislocation. The mechanism and treatment options remain unclear. In this case report, we describe a 31 year old man who sustained an isolated dorsal dislocation of the left tarsal naviculum, without fracture, when he was involved in a motor vehicle collision. The reported mechanism of the dislocation is a hyper plantar flexion force applied to the midfoot, resulting in a transient disruption of the ligamentous support of the naviculum bone, with dorsal displacement of the bone. The patient was treated with open reduction and Krischner-wire fixation of the navicular after the failure of closed reduction. The wires were removed after 6 weeks postoperatively. Physiotherapy for stiffness and midfoot pain was recommended for 2 months. At 6 months postoperatively, limping, midfoot pain and weakness were reported, no X-ray abnormalities were found. The patient returned to his obvious activities with a normal range of motion.

  7. Posterior Elbow Dislocation

    Directory of Open Access Journals (Sweden)

    Victoria Oppenheim

    2016-09-01

    Full Text Available History of present illness: A 15-year old female presented with left elbow pain. While competing in a high school wrestling match, she extended her left arm to brace a fall and had immediate onset of sharp pain. She denied weakness or numbness of her left arm. She had no past medical history. Significant findings: Elbow dislocations are classified by the position of the radio-ulnar joint relative to the humerus.1 Images 1, 2, and 3 show a left posterior elbow dislocation; the radius and ulna are displaced posteriorly with respect to the distal humerus. The lateral view of the elbow most clearly shows this: trochlear notch of the ulna is empty and displaced posteriorly relative to the trochlea. There is no associated fracture. Images 4 and 5 show the elbow status-post reduction, demonstrating proper alignment of the distal humerus with the radius and ulna. Discussion: Traumatic dislocations of the elbow are relatively uncommon in pediatric patients, with a peak incidence at 13 to 14 years.1 Dislocations are usually posterior and occur after forced abduction and extension of the elbow.1 It is important to evaluate for an associated fracture or avulsion, which occurs in over 50% of pediatric elbow dislocations. Fractures most commonly involve the medial epicondyle, radial head and neck, or coronoid process.1 One should also consider a neurovascular injury to the ulnar or median nerve or to the brachial artery or its branches.1 Posterior elbow dislocations should be reduced as soon as possible.1 Patients should receive adequate sedation and/or analgesia. One method of reduction is the “puller” technique, during which a practitioner stabilizes the humerus, while a second practitioner applies force against the anterior forearm, with gentle traction distally.1 Post-reduction neurovascular reassessment is important. After successful reduction, patients can be immobilized in a posterior long arm splint.

  8. Traumatic atlantooccipital dislocation.

    Science.gov (United States)

    Van den Bout, A H; Dommisse, G F

    1986-03-01

    A young adult sustained a traumatic atlantooccipital dislocation together with fracture-dislocation at C.4/5 level and had total neurologic deficit below C4 segment. He retained full consciousness but required respiratory support. He developed a stress ulcer with hemorrhage and evidence of "shock lung." He responded to intensive care. Surgery on the 11th day secured reduction and internal fixation at both levels. Death due to respiratory and cardiac arrest followed on the 14th day. Postmortem examination revealed edema of the brain and brainstem.

  9. Finite strain discrete dislocation plasticity

    NARCIS (Netherlands)

    Deshpande, VS; Needleman, A; Van der Giessen, E

    2003-01-01

    A framework for carrying out finite deformation discrete dislocation plasticity calculations is presented. The discrete dislocations are presumed to be adequately represented by the singular linear elastic fields so that the large deformations near dislocation cores are not modeled. The finite

  10. Medial subtalar dislocation

    African Journals Online (AJOL)

    Pr KODO

    A 27- year old female patient suffered from a closed medial subtalar dislocation treated by ... injury. She presented with pain, swelling of and internal rotation of the foot in relation to the knee joint. The talus was prominent dorsolaterally. Globally the clinical appearance was that ... frequently than the lateral ones and can be.

  11. Dislocated Worker Project.

    Science.gov (United States)

    1988

    Due to the severe economic decline in the automobile manufacturing industry in southeastern Michigan, a Dislocated Workers Program has been developed through the partnership of the Flint Area Chamber of Commerce, three community colleges, the National Center for Research in Vocational Education, the Michigan State Department of Education, the…

  12. Smectic meniscus and dislocations

    International Nuclear Information System (INIS)

    Geminard, J.C.; Oswald, P.; Holyst, R.

    1998-01-01

    In ordinary liquids the size of a meniscus and its shape is set by a competition between surface tension and gravity. The thermodynamical process of its creation can be reversible. On the contrary, in smectic liquid crystals the formation of the meniscus is always an irreversible thermodynamic process since it involves the creation of dislocations (therefore it involves friction). Also the meniscus is usually small in experiments with smectics in comparison to the capillary length and therefore the gravity does not play any role in determining the meniscus shape. Here we discuss the relation between dislocations and meniscus in smectics. The theoretical predictions are supported by a recent experiment performed on freely suspended films of smectic liquid crystals. In this experiment the measurement of the meniscus radius of curvature gives the pressure difference, Δp, according to the Laplace law. From the measurements of the growth dynamics of a dislocation loop (governed by Δp) we find the line tension (∼8 x 10 -8 dyn) and the mobility of an elementary edge dislocation (∼4 x 10 - 7 cm 2 s/g). (author)

  13. An Omni-Directional Wall-Climbing Microrobot with Magnetic Wheels Directly Integrated with Electromagnetic Micromotors

    Directory of Open Access Journals (Sweden)

    Xiaoning Tang

    2012-04-01

    Full Text Available This paper presents an omni-directional wall-climbing microrobot with magnetic wheels. The integral design with an actuator and adhesive is realized by integrating stators and rotors of an MEMS-based electromagnetic micromotor with a magnetic wheel. The omni-directional wall-climbing mechanism is designed by a set of steering gears and three standard magnetic wheels. The required torque and magnetic force for microrobot movement are derived by its static analysis. The size of the magnetic wheel is optimized, with consideration of its own design constraints, by ANSOFT and Pro/Engineer simulation so as to reduce unnecessary torque consumption under the same designed load. Related experiments demonstrate that the microrobot (diameter: 26mm; height: 16.4; mass: 7.2g; load capacity: 3g we have developed has a good wall-climbing ability and flexible mobility, and it can perform visual detection in a ferromagnetic environment.

  14. Dislocation of primary total hip arthroplasty and the risk of redislocation.

    LENUS (Irish Health Repository)

    Brennan, Stephen A

    2012-09-01

    6554 primary total hip arthroplasties were reviewed. Risk factors for dislocation were analysed to assess which were important in terms of predicting recurrent instability. The patients risk of having a second dislocation was independently associated with the surgical approach adopted (p = 0.03) and the time to first dislocation from the primary hip replacement (p = 0.002). Early dislocators whose surgery was performed through an anterolateral approach had less recurrence than late dislocators through a posterior or transtrochanteric approach. None of the other risk factors including head size (p = 0.59), modularity (p = 0.54), mechanism of dislocation (p = 0.23), leg length discrepancy (p = 0.69) and acetabular inclination (p = 0.31) were influential. The use of an abduction brace was not useful in preventing a further dislocation with 69.2% of those braced re-dislocating compared to 68.5% who were not braced (p = 0.96).

  15. Misfit dislocations of anisotropic magnetoresistant Nd0.45Sr0.55MnO3 thin films grown on SrTiO3 (1 1 0) substrates

    International Nuclear Information System (INIS)

    Tang, Y.L.; Zhu, Y.L.; Meng, H.; Zhang, Y.Q.; Ma, X.L.

    2012-01-01

    Nd 0.45 Sr 0.55 MnO 3 is an A-type antiferromagnetic manganite showing obvious angular-dependent magnetoresistance, which can be tuned by misfit strain. The misfit strain relaxation of Nd 0.45 Sr 0.55 MnO 3 thin films is of both fundamental and technical importance. In this paper, microstructures of epitaxial Nd 0.45 Sr 0.55 MnO 3 thin films grown on SrTiO 3 (1 1 0) substrates by pulsed laser deposition were investigated by means of (scanning) transmission electron microscopy. The Nd 0.45 Sr 0.55 MnO 3 thin films exhibit a two-layered structure: a continuous perovskite layer epitaxial grown on the substrate followed by epitaxially grown columnar nanostructures. An approximately periodic array of misfit dislocations is found along the interface with line directions of both 〈1 1 1〉 and [0 0 1]. High-resolution (scanning) transmission electron microscopy reveals that all the misfit dislocations possess a〈1 1 0〉-type Burgers vectors. A formation mechanism based on gliding or climbing of the dislocations is proposed to elucidate this novel misfit dislocation configuration. These misfit dislocations have complex effects on the strain relaxation and microstructure of the films, and thus their influence needs further consideration for heteroepitaxial perovskite thin film systems, especially for films grown on substrates with low-symmetry surfaces such as SrTiO 3 (1 1 0) and (1 1 1), which are attracting attention for their potentially new functions.

  16. Dechanneling by dislocation loops

    International Nuclear Information System (INIS)

    Chalant, Gerard.

    1976-09-01

    Ion implantation always induces the creation of dislocation loops. When the damage profile is determined by a backscattering technique, the dechanneling by these loops is implicitely at the origin of these measurements. The dechanneling of alpha particles by dislocation loops produced by the coalescence of quenched-in vacancies in aluminium is studied. The dechanneling and the concentration of loops were determined simultaneously. The dechanneling width around dislocation was found equal to lambda=6A, both for perfect and imperfect loops having a mean diameter d=250A. In the latter case, a dechanneling probability chi=0.34 was determined for the stacking fault, in good agreement with previous determination in gold. A general formula is proposed which takes into account the variation of lambda with the curvature (or the diameter d) of the loops. Finally, by a series of isothermal anneals, the self-diffusion energy ΔH of aluminium was measured. The value obtained ΔH=1.32+-0.10eV is in good agreement with the values obtained by other methods [fr

  17. Wall climbing in B. subtilis biofilms

    Science.gov (United States)

    Brenner, Michael P.; Branda, Steve

    2005-11-01

    B. subtilis produces surfactin which aids its spreading on the buffer, increasing the wetted area of a nutrient substrate. Synthesis of the surfactin polar group is regulated by a so called ``quorum sensing'' pathway so that effective quantities are produced only when the population density is high. We describe the implications for the simple case of wall-climbing swarms of bacteria, in which Marangoni stresses drive the swarm against gravity up an angled substrate, prior to the synthesis of an exopolysaccharide matrix that leads to the formation of a floating pellicle. Wrinkles observed on the mature pellicle are related to the familiar `tears of wine' instability.

  18. How Cr changes the dislocation core structure of α-Fe: the role of magnetism.

    Science.gov (United States)

    Zhang, Xu; Lu, Gang

    2013-02-27

    Cr is a critical alloying element in ferritic steels and its effect on the dislocation core structure of α-Fe is examined computationally using a quantum mechanics/molecular mechanics method. We find that Cr can significantly change the dislocation core structure of Fe where magnetism plays a crucial role. The strain-dependent magnetic interaction between Cr and the host Fe atoms is responsible for the dislocation core structure. When Cr is at the tension side of the slip plane, the Cr-Fe magnetic interaction is repulsive, which lowers the dislocation energy and pins the dislocation. When Cr occupies the compression side of the slip plane, the Cr-Fe interaction is attractive which increases the dislocation energy and promotes the dislocation to break away from Cr.

  19. Dislocation Interactions in Olivine Revealed by HR-EBSD

    Science.gov (United States)

    Wallis, David; Hansen, Lars N.; Britton, T. Ben; Wilkinson, Angus J.

    2017-10-01

    Interactions between dislocations potentially provide a control on strain rates produced by dislocation motion during creep of rocks at high temperatures. However, it has been difficult to establish the dominant types of interactions and their influence on the rheological properties of creeping rocks due to a lack of suitable observational techniques. We apply high-angular resolution electron backscatter diffraction to map geometrically necessary dislocation (GND) density, elastic strain, and residual stress in experimentally deformed single crystals of olivine. Short-range interactions are revealed by cross correlation of GND density maps. Spatial correlations between dislocation types indicate that noncollinear interactions may impede motion of proximal dislocations at temperatures of 1000°C and 1200°C. Long-range interactions are revealed by autocorrelation of GND density maps. These analyses reveal periodic variations in GND density and sign, with characteristic length scales on the order of 1-10 μm. These structures are spatially associated with variations in elastic strain and residual stress on the order of 10-3 and 100 MPa, respectively. Therefore, short-range interactions generate local accumulations of dislocations, leading to heterogeneous internal stress fields that influence dislocation motion over longer length scales. The impacts of these short- and/or long-range interactions on dislocation velocities may therefore influence the strain rate of the bulk material and are an important consideration for future models of dislocation-mediated deformation mechanisms in olivine. Establishing the types and impacts of dislocation interactions that occur across a range of laboratory and natural deformation conditions will help to establish the reliability of extrapolating laboratory-derived flow laws to real Earth conditions.

  20. Prediction of dislocation boundary characteristics

    DEFF Research Database (Denmark)

    Winther, Grethe

    orientation of the grain [1]. For selected boundaries it has been experimentally verified that the boundaries consist of fairly regular networks of dislocations, which come from the active slip systems [2]. The networks have been analyzed within the framework of Low-Energy-Dislocation-Structures (LEDS......, such as the dislocation content and misorientation. The prediction is based on the expected active slip systems and assumptions of mutual stress screening. In general, networks of dislocations with three linearly independent Burgers vectors fulfilling the criterion of mutual stress screening may form on any plane...

  1. Treating Proximal Interphalangeal Joint Dislocations.

    Science.gov (United States)

    Saitta, Bradley Hart; Wolf, Jennifer Moriatis

    2018-05-01

    Proximal interphalangeal (PIP) joint dislocation a common injury. Usually, concentric stable reduction can be achieved with closed reduction. Occasionally, PIP joint dislocations are irreducible and open reduction is necessary. Complications include prolonged splinting and delay in presentation with subluxation or persistent dislocation. Surgery is often recommended for contracture or joint reduction. Surgical techniques focus on contracture release, joint reduction, and range of motion. Techniques have evolved from primary repair to tenodesis and suture anchor reconstruction. Most studies on PIP joint dislocations are retrospective case reports with good outcomes but chronic mild contracture and deformity are consistent in the literature. Copyright © 2018 Elsevier Inc. All rights reserved.

  2. Dislocations in extruded Co-49.3 at. pct Al

    Science.gov (United States)

    Yaney, D. L.; Nix, W. D.; Pelton, A. R.

    1986-01-01

    Polycrystalline Co-49.3 at. pct Al, which had been extruded at 1505 K, was examined using transmission electron microscopy. Diffraction contrast analysis showed that b = 100 as well as b = 111 line dislocations contribute to elevated temperature deformation in CoAl. Therefore, it was concluded that sufficient slip systems exist in CoAl to allow for general plasticity in the absence of diffusional mechanisms. Line dislocations of the type b = 001 were observed on both 110 and 100 planes while b = 111 line dislocations were observed on 1 -1 0 planes.

  3. Climbing exercise increases bone mass and trabecular bone turnover through transient regulation of marrow osteogenic and osteoclastogenic potentials in mice.

    Science.gov (United States)

    Mori, Toshiharu; Okimoto, Nobukazu; Sakai, Akinori; Okazaki, Yuichi; Nakura, Nariaki; Notomi, Takuya; Nakamura, Toshitaka

    2003-11-01

    To investigate the relationship between the effects of bone turnover and bone marrow cell development in bone cells, we developed a mouse voluntary climbing exercise model. Climbing exercise increased bone volume and transient osteogenic potential of bone marrow. This model would be suitable for investigating the mechanistic roles of mechanical loading. The relationship between bone mass gain and local bone formation and resorption in mechanically loaded bone is not well understood. Sixty-five C57BL/6J mice, 8 weeks of age, were assigned to five groups: a baseline control and two groups each of ground control and climbing exercise mice for 2 and 4 weeks. Mice were housed in a 100-cm tower and had to climb toward a bottle placed at the top to drink water. Compared with the ground control, bone mineral density of the left femur increased in the climbing mice at 4 weeks. At 2 and 4 weeks, bone formation rate (BFR/BS) of periosteal surface, the cross-sectional area, and moment of inertia were increased in the climbing mice, whereas BFR/BS and eroded surface (ES/BS) of endosteal surface did not differ. The trabecular bone volume (BV/TV) of the proximal tibia increased in climbing mice, and osteoclast surface (Oc.S/BS) and osteoclast number decreased at 2 weeks. At 4 weeks, there were increases in BV/TV and parameters of bone formation, including mineralized surface, mineral apposition rate, and bone formation rate. In marrow cell cultures from the tibia, the number of alkaline phosphatase+ colony forming units-fibroblastic and the area of mineralized nodule formation in climbing mice were increased, and the number of osteoclast-like TRACP+ multinucleated cells was lower at 2 weeks. At 4 weeks, these parameters recovered to the levels of the ground controls. Our results indicate that climbing increased trabecular bone volume and reduced bone resorption, with a subsequent increase in bone formation. Intermittent climbing downregulates marrow osteoclastogenic cells and

  4. Wall Climbing Robot Using Electrostatic Adhesion Force Generated by Flexible Interdigital Electrodes

    Directory of Open Access Journals (Sweden)

    Rong Liu

    2013-01-01

    Full Text Available Electrostatic adhesion technology has broad application prospects on wall climbing robots because of its unique characteristics compared with other types of adhesion technologies. A double tracked wall climbing robot based on electrostatic adhesion technology is presented including electrode panel design, mechanical structure design, power supply system design and control system design. A theoretical adhesion model was established and the electrostatic potential and field were expressed by series expansions in terms of solutions of the Laplace function. Based on this model, the electrostatic adhesion force was calculated using the Maxwell stress tensor formulation. Several important factors which may influence the electrostatic adhesion force were analysed and discussed by both FEM simulation and theoretical calculation. In addition, experiments on the adhesion performance of the electrode panel and the climbing performance of the robot on various wall materials were carried out. Both the simulation and experiment results verify the feasibility of electrostatic adhesion technology being applied on wall climbing robots. The theoretical model and calculation method for the electrostatic adhesion force proposed in this paper are also justified.

  5. Comparative Effect of Forward and Backward Stair Climbing on ...

    African Journals Online (AJOL)

    olagbegi

    SUMMARY. Forward stair climbing (FSC) is associated with cardiovascular fitness benefits, but the training effects of backward stair climbing (BSC) have not been reported in the literature. This study compared the effects of 8 weeks of FSC and BSC on the cardiovascular parameters of apparently healthy young adults.

  6. Climbing ripple structure and associated storm-lamination from a ...

    Indian Academy of Sciences (India)

    with minor amounts of very fine quartz sand and silt. The climbing ripple structures exhibit a complex pattern of superposition of different types (type A, B and S) within cosets pointing to a fluctuating rate of suspension deposition versus bedform migration, and an unsteady character of the flow. Close association of climbing ...

  7. Forest climbing plants of West Africa: diversity, ecology and management

    NARCIS (Netherlands)

    Bongers, F.J.J.M.; Parren, M.P.E.; Traoré, D.

    2005-01-01

    Climbing plants, including lianas, represent a fascinating component of the ecology of tropical forests. This book focuses on the climbing plants of West African forests. Based on original research, it presents information on the flora (including a checklist), diversity (with overviews at several

  8. Comparative Effect of Forward and Backward Stair Climbing on ...

    African Journals Online (AJOL)

    Forward stair climbing (FSC) is associated with cardiovascular fitness benefits, but the training effects of backward stair climbing (BSC) have not been reported in the literature. This study compared the effects of 8 weeks of FSC and BSC on the cardiovascular parameters of apparently healthy young adults. Forty apparently ...

  9. On Climbing Scalars in String Theory

    CERN Document Server

    Dudas, E; Sagnotti, A

    2010-01-01

    In string models with "brane supersymmetry breaking" exponential potentials emerge at (closed-string) tree level but are not accompanied by tachyons. Potentials of this type have long been a source of embarrassment in flat space, but can have interesting implications for Cosmology. For instance, in ten dimensions the logarithmic slope |V'/V| lies precisely at a "critical" value where the Lucchin--Matarrese attractor disappears while the scalar field is \\emph{forced} to climb up the potential when it emerges from the Big Bang. This type of behavior is in principle perturbative in the string coupling, persists after compactification, could have trapped scalar fields inside potential wells as a result of the cosmological evolution and could have also injected the inflationary phase of our Universe.

  10. Nature of Dislocations in Silicon

    DEFF Research Database (Denmark)

    Hansen, Lars Bruno; Stokbro, Kurt; Lundqvist, Bengt

    1995-01-01

    Interaction between two partial 90 degrees edge dislocations is studied with atomic-scale simulations using the effective-medium tight-binding method. A large separation between the two dislocations (up to 30 Angstrom), comparable to experimental values, is achieved with a solution of the tight...

  11. Traumatic atlantooccipital dislocation. Case report.

    Science.gov (United States)

    Fruin, A H; Pirotte, T P

    1977-05-01

    A case of traumatic atlantooccipital dislocation is presented and the literature reviewed. This type of traumatic dislocation is probably produced by violent hyperextension of the upper cervical spine. Cranial nerve injuries and spinal cord injuries are common. Early fusion is recommended.

  12. Traumatic hip dislocations in children

    International Nuclear Information System (INIS)

    Minhas, M.S.

    2010-01-01

    Objectives: To evaluate clinical features, treatment and relationship to the time period between dislocation, reduction and early complications of traumatic dislocation of hip in children. Methods: Case series conducted at Jinnah Post Graduate Medical Centre Karachi from July 2005 to August 2009. Children with traumatic hip dislocation up to fifteen years of age who presented in last four years were included in this study. Their clinical information, etiology, associated injuries, duration, method of reduction and early complications are evaluated through emergency room proforma and indoor record. Follow up of patient was updated in outpatient department. Results: We had eight patients, six boys and two girls. Youngest 2.4 years and eldest was 12 years with mean age of 6.2 +- 3.8 years. All presented with posterior hip dislocation. Etiology was road traffic accident in two and history of fall in remaining six patients. Average duration of time between dislocation and reduction was 19 hours range 3-72 hours. Dislocated hips were reduced under General Anaesthesia in two patients and under sedation analgesia in six patients. No complications were noted in eight cases with mean 18.75 +- 13.23 months follows up. Conclusion: Traumatic hip dislocation in children is not rare. Slight trauma causes dislocation in younger age and immediate closed reduction and Immobilization reduces complications. (author

  13. A Splitting Scheme for Solving Reaction-Diffusion Equations Modeling Dislocation Dynamics in Materials Subjected to Cyclic Loading

    Science.gov (United States)

    Pontes, J.; Walgraef, D.; Christov, C. I.

    2010-11-01

    Strain localization and dislocation pattern formation are typical features of plastic deformation in metals and alloys. Glide and climb dislocation motion along with accompanying production/annihilation processes of dislocations lead to the occurrence of instabilities of initially uniform dislocation distributions. These instabilities result into the development of various types of dislocation micro-structures, such as dislocation cells, slip and kink bands, persistent slip bands, labyrinth structures, etc., depending on the externally applied loading and the intrinsic lattice constraints. The Walgraef-Aifantis (WA) (Walgraef and Aifanits, J. Appl. Phys., 58, 668, 1985) model is an example of a reaction-diffusion model of coupled nonlinear equations which describe 0 formation of forest (immobile) and gliding (mobile) dislocation densities in the presence of cyclic loading. This paper discuss two versions of the WA model and focus on a finite difference, second order in time 1-Nicolson semi-implicit scheme, with internal iterations at each time step and a spatial splitting using the Stabilizing, Correction (Christov and Pontes, Mathematical and Computer Modelling, 35, 87, 2002) for solving the model evolution equations in two dimensions. The results of two simulations are presented. More complete results will appear in a forthcoming paper.

  14. Temporomandibular joint dislocation in Nairobi.

    Science.gov (United States)

    Sang, L K; Mulupi, E; Akama, M K; Muriithi, J M; Macigo, F G; Chindia, M L

    2010-01-01

    Despite the diverse conservative and surgical modalities for the management of temporomandibular joint (TMJ) dislocation and the controversy that surrounds them, very little has been done within the East-African setup in terms of highlighting and provoking greater interest in the epidemiology and management of TMJ dislocation. To audit the pattern of occurrence, demographics, aetiology and enumerate the treatment modalities of TMJ dislocation at the oral and maxillofacial surgery division (OMFS) of the University of Nairobi Dental Hospital. Descriptive cross-sectional study. University of Nairobi Dental Hospital (UNDH) from January 1995 to July 2005. Twenty nine patients had been diagnosed and managed for TMJ dislocation. Twenty (69%) were females and nine (31%) were males. Their ages ranged from 10-95 years with a mean of 42 years. The cases managed were primarily chronic in nature. The most common form being anterior TMJ dislocation, accounting for twenty-five (86.2%) cases. Trauma was implicated as an aetiology in only five (17%) of the cases while the remaining majority of twenty four (83%) cases were spontaneous. Amongst the causes of spontaneous TMJ dislocation, yawning was the most common accounting for fourteen cases (48.3%). Dislocations caused by trauma were found to be 12.6 times more likely to be associated with other injuries than spontaneous dislocations. Anterior TMJ dislocations were found to be 1.3 times more likely to be associated with absence of molars than posterior TMJ dislocations. Anatomical aberrations, as predisposing factors, were not a significant finding in this research. Eight (28%) of the cases were managed conservatively. Twenty one (72%) of the cases were managed surgically. The eminectomy was the most common technique with a 75% success rate. The highest incidence of TMJ dislocation occurs in the 3rd-5th decade with a female preponderance with bilateral anterior TMJ dislocation being the most common. Most of the cases were managed

  15. Competing Grain Boundary and Interior Deformation Mechanisms with Varying Sizes

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Wei [University of Tennessee (UT); Gao, Yanfei [ORNL; Nieh, T. G. [University of Tennessee, Knoxville (UTK)

    2018-01-01

    In typical coarse-grained alloys, the dominant plastic deformations are dislocation gliding or climbing, and material strengths can be tuned by dislocation interactions with grain boundaries, precipitates, solid solutions, and other defects. With the reduction of grain size, the increase of material strengths follows the classic Hall-Petch relationship up to nano-grained materials. Even at room temperatures, nano-grained materials exhibit strength softening, or called the inverse Hall-Petch effect, as grain boundary processes take over as the dominant deformation mechanisms. On the other hand, at elevated temperatures, grain boundary processes compete with grain interior deformation mechanisms over a wide range of the applied stress and grain sizes. This book chapter reviews and compares the rate equation model and the microstructure-based finite element simulations. The latter explicitly accounts for the grain boundary sliding, grain boundary diffusion and migration, as well as the grain interior dislocation creep. Therefore the explicit finite element method has clear advantages in problems where microstructural heterogeneities play a critical role, such as in the gradient microstructure in shot peening or weldment. Furthermore, combined with the Hall-Petch effect and its breakdown, the above competing processes help construct deformation mechanism maps by extending from the classic Frost-Ashby type to the ones with the dependence of grain size.

  16. Numerical analysis of a unique mode of locomotion: vertical climbing by Pacific lamprey

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Q [Department of Structural Engineering, University of California, San Diego, La Jolla, CA (United States); Moser, M [Fish Ecology Division, Northwest Fisheries Science Center, National Marine Fisheries Service, Seattle, WA (United States); Kemp, P, E-mail: qizhu@ucsd.edu [International Centre for Ecohydraulics Research, Faculty of Engineering and the Environment, University of Southampton, Southampton (United Kingdom)

    2011-03-15

    Pacific lampreys are capable of climbing vertical wetted surfaces through a two-phase (bending and stretching) locomotion mode using the oral disc for adherence. We investigate the physical mechanism and performance of this process by using a continuous beam model. Two mechanisms, one akin to the jumping process and the other related to the fast stretching of the body, have been identified. This locomotion mode may inspire biomimetic designs of anguilliform swimming devices capable of overcoming steep obstacles. By using a genetic algorithm simulation we identify the combination of kinematic parameters corresponding to optimal efficiency (defined as the gravitational potential energy gained in each climbing step divided by the energy spent to activate the motion). These parameters are similar to laboratory observations of lamprey motion, suggesting that this type of locomotion has been optimized for maximum efficiency through evolution.

  17. Leaf mimicry in a climbing plant protects against herbivory.

    Science.gov (United States)

    Gianoli, Ernesto; Carrasco-Urra, Fernando

    2014-05-05

    Mimicry refers to adaptive similarity between a mimic organism and a model. Mimicry in animals is rather common, whereas documented cases in plants are rare, and the associated benefits are seldom elucidated [1, 2]. We show the occurrence of leaf mimicry in a climbing plant endemic to a temperate rainforest. The woody vine Boquila trifoliolata mimics the leaves of its supporting trees in terms of size, shape, color, orientation, petiole length, and/or tip spininess. Moreover, sequential leaf mimicry occurs when a single individual vine is associated with different tree species. Leaves of unsupported vines differed from leaves of climbing plants closely associated with tree foliage but did not differ from those of vines climbing onto leafless trunks. Consistent with an herbivory-avoidance hypothesis, leaf herbivory on unsupported vines was greater than that on vines climbing on trees but was greatest on vines climbing onto leafless trunks. Thus, B. trifoliolata gains protection against herbivory not merely by climbing and thus avoiding ground herbivores [3] but also by climbing onto trees whose leaves are mimicked. Unlike earlier cases of plant mimicry or crypsis, in which the plant roughly resembles a background or color pattern [4-7] or mimics a single host [8, 9], B. trifoliolata is able to mimic several hosts. Copyright © 2014 Elsevier Ltd. All rights reserved.

  18. Irradiation deformation due to SIPA induced dislocation anisotropy

    International Nuclear Information System (INIS)

    Woo, CH.

    1980-02-01

    A contribution to irradiation deformation resulting from the stress-induced preferred adsorption (SIPA) effect is considered. SIPA causes a variation of the growth rates of irradiation-generated dislocation loops, according to the alignment of their Burgers vectors with respect to the applied stress. A prolinged period under an applied stress then creates an anisotropic dislocation structure in which the majority of dislocations have their Burgers vectors in alignment with the stress. In the presence of 'neutral' sinks, the resulting anisotropic dislocation structure causes plastic deformation similar to the way in which irradiation growth occurs in zirconium. This mechanism is called SIPA-induced growth (SIG). We have shown that SIG is very significant in comparison to SIPA, except when little or no loop growth has occurred during the period the stress is applied. This report contains the detailed formulation and derivation of the formulae for the evaluation of the contribution due to SIG. (auth)

  19. Scaling and biomechanics of surface attachment in climbing animals

    Science.gov (United States)

    Labonte, David; Federle, Walter

    2015-01-01

    Attachment devices are essential adaptations for climbing animals and valuable models for synthetic adhesives. A major unresolved question for both natural and bioinspired attachment systems is how attachment performance depends on size. Here, we discuss how contact geometry and mode of detachment influence the scaling of attachment forces for claws and adhesive pads, and how allometric data on biological systems can yield insights into their mechanism of attachment. Larger animals are expected to attach less well to surfaces, due to their smaller surface-to-volume ratio, and because it becomes increasingly difficult to distribute load uniformly across large contact areas. In order to compensate for this decrease of weight-specific adhesion, large animals could evolve overproportionally large pads, or adaptations that increase attachment efficiency (adhesion or friction per unit contact area). Available data suggest that attachment pad area scales close to isometry within clades, but pad efficiency in some animals increases with size so that attachment performance is approximately size-independent. The mechanisms underlying this biologically important variation in pad efficiency are still unclear. We suggest that switching between stress concentration (easy detachment) and uniform load distribution (strong attachment) via shear forces is one of the key mechanisms enabling the dynamic control of adhesion during locomotion. PMID:25533088

  20. Bio-inspired step-climbing in a hexapod robot.

    Science.gov (United States)

    Chou, Ya-Cheng; Yu, Wei-Shun; Huang, Ke-Jung; Lin, Pei-Chun

    2012-09-01

    Inspired by the observation that the cockroach changes from a tripod gait to a different gait for climbing high steps, we report on the design and implementation of a novel, fully autonomous step-climbing maneuver, which enables a RHex-style hexapod robot to reliably climb a step up to 230% higher than the length of its leg. Similar to the climbing strategy most used by cockroaches, the proposed maneuver is composed of two stages. The first stage is the 'rearing stage,' inclining the body so the front side of the body is raised and it is easier for the front legs to catch the top of the step, followed by the 'rising stage,' maneuvering the body's center of mass to the top of the step. Two infrared range sensors are installed on the front of the robot to detect the presence of the step and its orientation relative to the robot's heading, so that the robot can perform automatic gait transition, from walking to step-climbing, as well as correct its initial tilt approaching posture. An inclinometer is utilized to measure body inclination and to compute step height, thus enabling the robot to adjust its gait automatically, in real time, and to climb steps of different heights and depths successfully. The algorithm is applicable for the robot to climb various rectangular obstacles, including a narrow bar, a bar and a step (i.e. a bar of infinite width). The performance of the algorithm is evaluated experimentally, and the comparison of climbing strategies and climbing behaviors in biological and robotic systems is discussed.

  1. Bio-inspired step-climbing in a hexapod robot

    International Nuclear Information System (INIS)

    Chou, Ya-Cheng; Yu, Wei-Shun; Huang, Ke-Jung; Lin, Pei-Chun

    2012-01-01

    Inspired by the observation that the cockroach changes from a tripod gait to a different gait for climbing high steps, we report on the design and implementation of a novel, fully autonomous step-climbing maneuver, which enables a RHex-style hexapod robot to reliably climb a step up to 230% higher than the length of its leg. Similar to the climbing strategy most used by cockroaches, the proposed maneuver is composed of two stages. The first stage is the ‘rearing stage,’ inclining the body so the front side of the body is raised and it is easier for the front legs to catch the top of the step, followed by the ‘rising stage,’ maneuvering the body's center of mass to the top of the step. Two infrared range sensors are installed on the front of the robot to detect the presence of the step and its orientation relative to the robot's heading, so that the robot can perform automatic gait transition, from walking to step-climbing, as well as correct its initial tilt approaching posture. An inclinometer is utilized to measure body inclination and to compute step height, thus enabling the robot to adjust its gait automatically, in real time, and to climb steps of different heights and depths successfully. The algorithm is applicable for the robot to climb various rectangular obstacles, including a narrow bar, a bar and a step (i.e. a bar of infinite width). The performance of the algorithm is evaluated experimentally, and the comparison of climbing strategies and climbing behaviors in biological and robotic systems is discussed. (paper)

  2. Dislocation Starvation and Exhaustion Hardening in Mo-alloy Nanofibers

    Energy Technology Data Exchange (ETDEWEB)

    Chisholm, Claire [University of California, Berkeley & LBNL; Bei, Hongbin [ORNL; Lowry, M. B. [University of California, Berkeley; Oh, Jason [Hysitron, Inc., MN; Asif, S.A. Syed [Hysitron, Inc., MN; Warren, O. [Hysitron, Inc., MN; Shan, Zhiwei [Xi' an Jiaotong University, China & Hysitron, Inc., MN; George, Easo P [ORNL; Minor, Andrew [University of California, Berkeley & LBNL

    2012-01-01

    The evolution of defects in Mo alloy nanofibers with initial dislocation densities ranging from 0 to 1.6 1014 m2 were studied using an in situ push-to-pull device in conjunction with a nanoindenter in a transmission electron microscope. Digital image correlation was used to determine stress and strain in local areas of deformation. When they had no initial dislocations the Mo alloy nanofibers suffered sudden catastrophic elongation following elastic deformation to ultrahigh stresses. At the other extreme fibers with a high dislocation density underwent sustained homogeneous deformation after yielding at much lower stresses. Between these two extremes nanofibers with intermediate dislocation densities demonstrated a clear exhaustion hardening behavior, where the progressive exhaustion of dislocations and dislocation sources increases the stress required to drive plasticity. This is consistent with the idea that mechanical size effects ( smaller is stronger ) are due to the fact that nanostructures usually have fewer defects that can operate at lower stresses. By monitoring the evolution of stress locally we find that exhaustion hardening causes the stress in the nanofibers to surpass the critical stress predicted for self-multiplication, supporting a plasticity mechanism that has been hypothesized to account for the rapid strain softening observed in nanoscale bcc materials at high stresses.

  3. A discrete dislocation dynamics model of creeping single crystals

    Science.gov (United States)

    Rajaguru, M.; Keralavarma, S. M.

    2018-04-01

    Failure by creep is a design limiting issue for metallic materials used in several high temperature applications. Current theoretical models of creep are phenomenological with little connection to the underlying microscopic mechanisms. In this paper, a bottom-up simulation framework based on the discrete dislocation dynamics method is presented for dislocation creep aided by the diffusion of vacancies, known to be the rate controlling mechanism at high temperature and stress levels. The time evolution of the creep strain and the dislocation microstructure in a periodic unit cell of a nominally infinite single crystal is simulated using the kinetic Monte Carlo method, together with approximate constitutive laws formulated for the rates of thermal activation of dislocations over local pinning obstacles. The deformation of the crystal due to dislocation glide between individual thermal activation events is simulated using a standard dislocation dynamics algorithm, extended to account for constant stress periodic boundary conditions. Steady state creep conditions are obtained in the simulations with the predicted creep rates as a function of stress and temperature in good agreement with experimentally reported values. Arrhenius scaling of the creep rates as a function of temperature and power-law scaling with the applied stress are also reproduced, with the values of the power-law exponents in the high stress regime in good agreement with experiments.

  4. Epidemiology of Elbow Dislocations in High School Athletes.

    Science.gov (United States)

    Dizdarevic, Ismar; Low, Sara; Currie, Dustin W; Comstock, R Dawn; Hammoud, Sommer; Atanda, Alfred

    2016-01-01

    The elbow is the second most commonly dislocated major joint in the general population. Previous studies that focused on emergency department populations indicate that such injuries occur most frequently among adolescent athletes. To describe the epidemiological rates and patterns of sports-related elbow dislocations in high school athletes. Descriptive epidemiology study. Sports-related injury data for the 2005-2006 through 2013-2014 academic years from a national convenience sample of high schools participating in the National High School Sports-Related Injury Surveillance Study (High School Reporting Information Online [RIO]) were analyzed. Certified athletic trainers participating in High School RIO reported 115 of 1246 (9.2%) elbow injuries as elbow dislocations. A total of 30,415,179 athlete exposures (AEs) were reported during the study period, resulting in a dislocation rate of 0.38 per 100,000 AEs. The majority of the dislocations resulted from boys' wrestling (46.1%) and football (37.4%). Elbow dislocation rates were higher in competition than in practice. Also, 91.3% of dislocations occurred in boys' sports. Among both boys (60.4%) and girls (88.9%), the majority of injuries occurred during varsity sports activities. Contact with another person was the most common injury mechanism (46.9%), followed by contact with the playing surface (46.0%). Dislocations more commonly resulted in removal from play for more than 3 weeks (23.4% vs 6.9%, respectively) or medical disqualification (36.9% vs 7.0%, respectively) compared with other elbow injuries. Dislocations were also more likely to result in surgical treatment than other elbow injuries (13.6% vs 4.7%, respectively). In high school athletes, elbow dislocations result in longer removal from play and are more likely to require surgical treatment than nondislocation-associated elbow injuries. Rates and patterns of elbow dislocations vary by sport. In high-risk sports, focused sport-specific prevention

  5. Modeling of dislocation channel width evolution in irradiated metals

    Science.gov (United States)

    Doyle, Peter J.; Benensky, Kelsa M.; Zinkle, Steven J.

    2018-02-01

    Defect-free dislocation channel formation has been reported to promote plastic instability during tensile testing via localized plastic flow, leading to a distinct loss of ductility and strain hardening in many low-temperature irradiated materials. In order to study the underlying mechanisms governing dislocation channel width and formation, the channel formation process is modeled via a simple stochastic dislocation-jog process dependent upon grain size, defect cluster density, and defect size. Dislocations traverse a field of defect clusters and jog stochastically upon defect interaction, forming channels of low defect-density. Based upon prior molecular dynamics (MD) simulations and in-situ experimental transmission electron microscopy (TEM) observations, each dislocation encounter with a dislocation loop or stacking fault tetrahedron (SFT) is assumed to cause complete absorption of the defect cluster, prompting the dislocation to jog up or down by a distance equal to half the defect cluster diameter. Channels are predicted to form rapidly and are comparable to reported TEM measurements for many materials. Predicted channel widths are found to be most strongly dependent on mean defect size and correlated well with a power law dependence on defect diameter and density, and distance from the dislocation source. Due to the dependence of modeled channel width on defect diameter and density, maximum channel width is predicted to slowly increase as accumulated dose increases. The relatively weak predicted dependence of channel formation width with distance, in accordance with a diffusion analogy, implies that after only a few microns from the source, most channels observed via TEM analyses may not appear to vary with distance because of limitations in the field-of-view to a few microns. Further, examinations of the effect of the so-called "source-broadening" mechanism of channel formation showed that its effect is simply to add a minimum thickness to the channel

  6. Bilateral anterior dislocation of the shoulders at the start of a backstroke competition.

    Science.gov (United States)

    Dlimi, Fayçal; Rhanim, Abdelkarim; Lahlou, Abdou; Kharmaz, Mohammed; Ouadghiri, Mohammed; El Bardouni, Ahmed; Berrada, Mohamed Saleh; Mahfoud, Mustapha; El Yaacoubi, Moradh

    2012-03-01

    Bilateral anterior dislocation of the shoulders is very rare. A 20-year-old man presented with bilateral anterior shoulder dislocation as a result of a diving incident. He complained of pain and restriction of movement in both shoulders with abducted and externally rotated arms. Radiographs revealed that the shoulders were dislocated. The patient was treated with closed reduction and was able to resume swimming 3 months later. To our knowledge, this is the first bilateral anterior dislocation of the shoulders during a backstroke swimming competition that was caused by this mechanism of injury. The rarity of this lesion and its uncommon mechanism prompted us to relate this observation.

  7. Knee Dislocations in Sports Injuries

    Science.gov (United States)

    Pardiwala, Dinshaw N; Rao, Nandan N; Anand, Karthik; Raut, Alhad

    2017-01-01

    Knee dislocations are devastating when they occur on the athletic field or secondary to motor sports. The complexity of presentation and spectrum of treatment options makes these injuries unique and extremely challenging to even the most experienced knee surgeons. An astute appreciation of the treatment algorithm is essential to plan individualized management since no two complex knee dislocations are ever the same. Moreover, attention to detail and finesse of surgical technique are required to obtain a good functional result and ensure return to play. Over the past 10 years, our service has treated 43 competitive sportsmen with knee dislocations, and this experience forms the basis for this narrative review. PMID:28966379

  8. Traumatic atlantooccipital dislocation with survival.

    Science.gov (United States)

    Woodring, J H; Selke, A C; Duff, D E

    1981-07-01

    Traumatic atlantooccipital dislocation is generally considered incompatible with life. However, there have been isolated survivals from this injury, and a few patients initially have minimal neurologic deficits disproportionate to the gravity of their injury, a feature that has not been adequately stressed. The potentially catastrophic results of delayed therapy make early radiographic detection imperative. Marked retropharyngeal soft-tissue swelling, an abnormal basion-odontoid alignment, and posterior displacement of the atlas are diagnostic of anterior atlantooccipital dislocation. In the more uncommon posterior atlantooccipital dislocation an abnormal basion-odontoid alignment associated with marked soft-tissue swelling should suggest the correct diagnosis. Conventional tomography can be confirmatory.

  9. Self-organization of voids, gas bubbles and dislocation patterns under irradiation

    International Nuclear Information System (INIS)

    Dubinko, V.I.; Turkin, A.A.

    1993-01-01

    In the present paper three examples of self-organization in solids under irradiation are considered on the basis of original mechanisms, namely, the ordering of voids in void lattices under high temperature irradiation, the alignment of gas bubbles in bubble lattices under low-temperature gas atom implantation, and the formation of superdislocations (one-dimensional pile-ups of dislocation loops) and other dislocation patterns in the regimes of medium and high temperature irradiation. The ordering of cavities (i.e.voids or gas bubbles) is shown to arise due to a dissipative interaction between cavities induced by the interstitial dislocation loop absorption and punching, respectively, which represent anisotropic mechanisms of atomic transport. The dislocation patterning is shown to be driven by the dependence of dislocation bias for absorption of self-interstitial atoms on the dislocation arrangement. (author). 57 refs., 1 tab., 12 figs

  10. Growth and dislocation studies of β-HMX.

    Science.gov (United States)

    Gallagher, Hugh G; Sherwood, John N; Vrcelj, Ranko M

    2014-01-01

    The defect structure of organic materials is important as it plays a major role in their crystal growth properties. It also can play a subcritical role in "hot-spot" detonation processes of energetics and one such energetic is cyclotetramethylene-tetranitramine, in the commonly used beta form (β-HMX). The as-grown crystals grown by evaporation from acetone show prismatic, tabular and columnar habits, all with {011}, {110}, (010) and (101) faces. Etching on (010) surfaces revealed three different types of etch pits, two of which could be identified with either pure screw or pure edge dislocations, the third is shown to be an artifact of the twinning process that this material undergoes. Examination of the {011} and {110} surfaces show only one type of etch pit on each surface; however their natural asymmetry precludes the easy identification of their Burgers vector or dislocation type. Etching of cleaved {011} surfaces demonstrates that the etch pits can be associated with line dislocations. All dislocations appear randomly on the crystal surfaces and do not form alignments characteristic of mechanical deformation by dislocation slip. Crystals of β-HMX grown from acetone show good morphological agreement with that predicted by modelling, with three distinct crystal habits observed depending upon the supersaturation of the growth solution. Prismatic habit was favoured at low supersaturation, while tabular and columnar crystals were predominant at higher super saturations. The twin plane in β-HMX was identified as a (101) reflection plane. The low plasticity of β-HMX is shown by the lack of etch pit alignments corresponding to mechanically induced dislocation arrays. On untwinned {010} faces, two types of dislocations exist, pure edge dislocations with b = [010] and pure screw dislocations with b = [010]. On twinned (010) faces, a third dislocation type exists and it is proposed that these pits are associated with pure screw dislocations with b = [010

  11. Human climbing with efficiently scaled gecko-inspired dry adhesives.

    Science.gov (United States)

    Hawkes, Elliot W; Eason, Eric V; Christensen, David L; Cutkosky, Mark R

    2015-01-06

    Since the discovery of the mechanism of adhesion in geckos, many synthetic dry adhesives have been developed with desirable gecko-like properties such as reusability, directionality, self-cleaning ability, rough surface adhesion and high adhesive stress. However, fully exploiting these adhesives in practical applications at different length scales requires efficient scaling (i.e. with little loss in adhesion as area grows). Just as natural gecko adhesives have been used as a benchmark for synthetic materials, so can gecko adhesion systems provide a baseline for scaling efficiency. In the tokay gecko (Gekko gecko), a scaling power law has been reported relating the maximum shear stress σmax to the area A: σmax ∝ A(-1/4). We present a mechanical concept which improves upon the gecko's non-uniform load-sharing and results in a nearly even load distribution over multiple patches of gecko-inspired adhesive. We created a synthetic adhesion system incorporating this concept which shows efficient scaling across four orders of magnitude of area, yielding an improved scaling power law: σmax ∝ A(-1/50). Furthermore, we found that the synthetic adhesion system does not fail catastrophically when a simulated failure is induced on a portion of the adhesive. In a practical demonstration, the synthetic adhesion system enabled a 70 kg human to climb vertical glass with 140 cm(2) of adhesive per hand. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

  12. Neglected locked vertical patellar dislocation

    Directory of Open Access Journals (Sweden)

    Rakesh Kumar Gupta

    2012-01-01

    Full Text Available Patellar dislocations occurring about the vertical and horizontal axis are rare and irreducible. The neglected patellar dislocation is still rarer. We describe the clinical presentation and management of a case of neglected vertical patellar dislocation in a 6 year-old boy who sustained an external rotational strain with a laterally directed force to his knee. Initially the diagnosis was missed and 2 months later open reduction was done. The increased tension generated by the rotation of the lateral extensor retinaculum kept the patella locked in the lateral gutter even with the knee in full extension. Traumatic patellar dislocation with rotation around a vertical axis has been described earlier, but no such neglected case has been reported to the best of our knowledge.

  13. Arthroscopic treatment of acromioclavicular dislocation

    OpenAIRE

    Mihai T. Gavrilă; Ștefan Cristea

    2017-01-01

    A thorough understanding of biomechanical function of both acromioclavicular (AC) and coracoclavicular (CC) ligaments, stimulated surgeons to repair high-grade AC dislocation using arthroscopic technique. This technique necessitates a clear understanding of shoulder anatomy, especially of the structures in proximity to the clavicle and coracoid process and experiences in arthroscopic surgery. The follow case describes an arthroscopic technique used to treat AC dislocation in young man 30 year...

  14. Dislocation movement and hysteresis in Maraging blades

    Energy Technology Data Exchange (ETDEWEB)

    Di Cintio, Arianna; Ascione, Maria; De Salvo, Riccardo [LIGO Laboratory, California Institute of Technology, MS 18-34, 1200 E.California Blvd., Pasadena, CA, 91125 (United States); Marchesoni, Fabio [INFN-VIRGO Project Dipartimento di Fisica, Universita' di Camerino, I-62032 Camerino (Italy); Bhawal, Abhik, E-mail: desalvo@ligo.caltech.ed [Arcadia High School, Arcadia, CA (United States)

    2009-10-21

    All seismic isolation systems developed for gravitational-wave interferometric detectors, such as LIGO, Virgo and TAMA, make use of Maraging steel blades. The dissipation properties of these blades have been studied at low frequencies, by using a geometric anti-spring (GAS) filter, which allowed the exploration of resonant frequencies below 100 mHz. At this frequency an anomalous transfer function was observed in the GAS filter: this is one of several motivations for this work. The many unexpected effects observed and measured are explainable by the collective movement of dislocations inside the material described with the statistic of self-organised criticality. At low frequencies, below 200 mHz, the dissipation mechanism can subtract elasticity from the system even leading to sudden collapse. While Young's modulus is weaker, excess dissipation is observed. At higher frequencies the applied stress is probably too fast to allow the full growth of dislocation avalanches, and less losses are observed, thus explaining the higher Q-factor in this frequency range. The domino effect that leads to the release of entangled dislocations allows the understanding of the random walk of the Virgo and TAMA inverted pendula, the anomalous GAS filter transfer function as well as the loss of predictability of the ring-down decay in the LIGO seismic attenuation system inverted pendula.

  15. A Survey of Wall Climbing Robots: Recent Advances and Challenges

    OpenAIRE

    Shunsuke Nansai; Rajesh Elara Mohan

    2016-01-01

    In recent decades, skyscrapers, as represented by the Burj Khalifa in Dubai and Shanghai Tower in Shanghai, have been built due to the improvements of construction technologies. Even in such newfangled skyscrapers, the façades are generally cleaned by humans. Wall climbing robots, which are capable of climbing up vertical surfaces, ceilings and roofs, are expected to replace the manual workforce in façade cleaning works, which is both hazardous and laborious work. Such tasks require these rob...

  16. The flexor tendon pulley system and rock climbing.

    Science.gov (United States)

    Crowley, Timothy P

    2012-06-01

    Rock climbing has increased in popularity over the past two decades. Closed traumatic rupture of the finger flexor tendon pulleys is rare among the general population but is seen much more commonly in rock climbers. This article reviews the anatomy and biomechanics of the finger flexor tendon pulleys, how they may be injured in rock climbing and how these injuries are best diagnosed and managed.

  17. Reliable Stair Climbing in the Simple Hexapod ’RHex’

    Science.gov (United States)

    2002-01-01

    legged robots have successfully climbed stairs – recently the Honda bipeds climbed quasi- statically.6 Raibert built a biped that could hop over...cim.mcgill.ca, fgrimminger@web.de, buehler@cim.mcgill.ca Ambulatory Robotics Laboratory, Centre for Intelligent Machines, McGill University Montreal, Quebec...this paper, we describe an open loop controller that enables our small robot (Length: 51 cm, Width: 20 cm, Height: 12.7 cm. Leg length: 16 cm), to

  18. HRTEM studies of dislocations in cubic BN

    International Nuclear Information System (INIS)

    Nistor, L.C.; Tendeloo, G. van; Dinca, G.

    2004-01-01

    The atomic structure of dislocations in cubic boron nitride has been investigated by high resolution transmission electron microscopy. Most of the perfect dislocations, screw and 60 edge, are dissociated. A 60 dislocation which was undissociated has been analysed. Computer simulation is performed in an attempt to characterise the core structure. Twinning dislocations and dislocations resulting from the intersection of stacking faults are also revealed. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. HRTEM studies of dislocations in cubic BN

    Energy Technology Data Exchange (ETDEWEB)

    Nistor, L.C. [National Institute for Materials Physics, P.O. Box MG-7 Magurele, 077125 Bucharest (Romania); Tendeloo, G. van [University of Antwerp, EMAT, Groenenborgerlaan 171, 2020 Antwerp (Belgium); Dinca, G. [Dacia Synthetic Diamond Factory, Timisoara av. 5, P.O. Box 58-52, 077350 Bucharest (Romania)

    2004-09-01

    The atomic structure of dislocations in cubic boron nitride has been investigated by high resolution transmission electron microscopy. Most of the perfect dislocations, screw and 60 edge, are dissociated. A 60 dislocation which was undissociated has been analysed. Computer simulation is performed in an attempt to characterise the core structure. Twinning dislocations and dislocations resulting from the intersection of stacking faults are also revealed. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  20. Trans-triquetral Perilunate fracture dislocation

    OpenAIRE

    John-Henry Rhind; Abhinav Gulihar; Andrew Smith

    2018-01-01

    Perilunate dislocations and perilunate fracture dislocations are rare and serious injuries. Perilunate dislocations represent less than 10% of all carpal injuries of which 61% represent transcaphoid fractures. Because of their rarity, up to 25% of perilunate dislocations are initially missed on first assessment. We present the case of a 66-year-old-gentleman who sustained an isolated trans-triquetral perilunate fracture dislocation while walking his dog. This was diagnosed in the emergency de...

  1. Perilunar carpal dislocations treatment outcome.

    Science.gov (United States)

    Gagała, Jacek; Tarczyńska, Marta; Kosior, Piotr

    2006-06-30

    Background. The aim of the study was to analyze late outcomes of perilunar carpal dislocations, depending on the type of the injury, time of the diagnosis and the treatment methods. Material and methods. The material is constituted by 37 patients treated in our department between 1981-2004 because of perilunar dislocation. In group were 2 women and 35 men, aged 19-56 (mean 31 years). All patients were asked for control visit. DASH and Mayo score were used to evaluate the outcome. Range of wrist motion, its stability, grip strength and X-ray pictures were analyzed. Results. Better follow-up results were observed in persons with early diagnosed dislocations of the wrist. The best outcomes were observed in group with perilunar early diagnosed dislocations, which were treated by open reduction. Posttraumatic wrist instability often was diagnosed in patients with dislocation of lunar bone and late-diagnosed transscaphoid perilunar carpal dislocations. Conclusions. The data we obtained show, that the consequences of late-diagnosed and late-treated injuries of the wrist are instability, pain, decrease in range of motion and hand skills.

  2. Interstitial impurity interactions and dislocation microdynamics in Mo crystals

    International Nuclear Information System (INIS)

    Kwok, D.N.

    1975-05-01

    The effects of interstitial impurities on the mechanical properties of molybdenum are explored by comparing results obtained for crystals of various interstitial contents controlled by ultra-high vacuum outgassing. Results show a modulus reduction for as-grown samples and for outgassed specimens at low applied stresses. As a function of plastic microstrain, the values of modulus defect for both as-grown and outgassed specimens saturate at the same value. Interstitial impurities act as pinning agents to dislocation bowing, but when all the easy dislocation loops have broken away from local interstitial pins, the modulus defect reaches a constant saturation value. Etch pitting techniques were used to correlate microstrain observations with dislocation generation and motion. It has been found that edge dislocation generation and movement are active in the microstrain region while screw dislocations are relatively inactive until the macrostrain region is reached. Dislocation velocities range from 10 -6 to 10 -3 cm/s and the average distance between interstitial impurity pinning points is found to be approximately 8 x 10 -4 cm. (U.S.)

  3. Disassembly and Dislocation of a Bipolar Hip Prosthesis

    Directory of Open Access Journals (Sweden)

    Hsieh-Hsing Lee

    2008-01-01

    Full Text Available Dislocation of a hip prosthesis is a common complication. In usual cases of hip prosthesis dislocation, the prosthetic femoral head comes out from either the natural acetabular cavity in a bipolar hemiarthroplasty or the prosthetic acetabulum in a total hip arthroplasty. Only a few cases of bipolar hip prosthesis dislocation due to dissociation between the polyethylene and inner head of the prosthesis have been reported. We describe a rare case of disassembly of the inner head from the bipolar outer prosthesis in an osteoarthritic acetabulum. A 72-year-old woman had undergone bipolar hemiarthroplasty due to fracture of the left femoral neck about 10 years previously. Recently, she sustained an injury after falling from a chair, and examinations revealed an unusual disassembly−dislocation of the bipolar hip prosthesis. We classified this failure in our patient as a type II failure, representing extreme varus position of the outer head in the acetabulum, dislocation of the inner head from the outer head, and a detached locking ring around the stem neck. This mechanism of failure as shown in our patient rarely occurs in the bipolar prosthesis of the self-centering system. Osteoarthritic change of the acetabulum would place the outer head in the varus position, increasing wear on the beveled rim by impinging the femoral stem neck and causing dislodgment of the inner locking ring and consequent disassembly−dislocation of the inner head.

  4. Modeling and analysis of a meso-hydraulic climbing robot with artificial muscle actuation.

    Science.gov (United States)

    Chapman, Edward M; Jenkins, Tyler E; Bryant, Matthew

    2017-07-10

    This paper presents a fully coupled electro-hydraulic model of a bio-inspired climbing robot actuated by fluidic artificial muscles (FAMs). This analysis expands upon previous FAM literature by considering not only the force and contraction characteristics of the actuator, but the complete hydraulic and electromechanical circuits as well as the dynamics of the climbing robot. This analysis allows modeling of the time-varying applied pressure, electrical current, and actuator contraction for accurate prediction of the robot motion, energy consumption, and mechanical work output. The developed model is first validated against mechanical and electrical data collected from a proof-of-concept prototype robot. The model is then employed to study the system-level sensitivities of the robot locomotion efficiency and average climbing speed to several design and operating parameters. The results of this analysis demonstrate that considering only the transduction efficiency of the FAM actuators is insufficient to maximize the efficiency of the complete robot, and that a holistic approach can lead to significant improvements in performance. © 2017 IOP Publishing Ltd.

  5. Dislocation structure evolution and characterization in the compression deformed Mn-Cu alloy

    International Nuclear Information System (INIS)

    Zhong, Y.; Yin, F.; Sakaguchi, T.; Nagai, K.; Yang, K.

    2007-01-01

    Dislocation densities and dislocation structure arrangements in cold compressed polycrystalline commercial M2052 (Mn-20Cu-5Ni-2Fe) high damping alloy with various strains were determined in scanning mode by X-ray peak profile analysis and electron backscatter diffraction (EBSD). The results indicate that the Mn-Cu-Ni-Fe alloy has an evolution behavior quite similar to the dislocation structure in copper. The dislocation arrangement parameter shows a local minimum in the transition range between stages III and IV that can be related to the transformation of the dislocation arrangement in the cell walls from a polarized dipole wall (PDW) into a polarized tile wall (PTW) structure. This evolution is further confirmed by the results of local misorientation determined by EBSD. In addition, during deformation, the multiplication of dislocation densities in the MnCu alloy is significantly slower than that in copper, and the transition of the dislocation structure is strongly retarded in the MnCu alloy compared with copper. These results can be explained by the mechanism of elastic anisotropy on the dislocation dynamics, as the elastic anisotropy in the MnCu alloy is larger than that in copper, which can strongly retard the multiplication of the dislocation population and the transformation of the dislocation structure. These results are important for research into the plastic working behavior of Mn-Cu-Ni-Fe high damping alloy

  6. Mouse shoulder morphology responds to locomotor activity and the kinematic differences of climbing and running.

    Science.gov (United States)

    Green, David J; Richmond, Brian G; Miran, Sara L

    2012-12-01

    Mechanical loads play a significant role in determining long bone shape and strength, but less work has explored how these loads influence flat bones like the scapula, which has been shown to vary with locomotor preference among primate taxa. Here, we tested the effects of voluntary running and climbing exercise in mice to examine how the mechanical loads borne from different locomotor patterns influence shoulder morphological development. Ninety-nine female wild-type mice were distributed equally among sedentary control, activity-wheel running, and vertical climbing experimental conditions. Running mice had the lowest body masses, larger intrinsic shoulder muscles, and the most pronounced differences in scapular size and shape relative to the other groups. Climbing mouse scapular morphology also differed significantly from the control individuals, but these differences were not as marked as those between the running and control mice. This might be attributable in part to greater levels of activity in the wheel-runners relative to the climbers. Additionally, climbing mice held their bodies closer to the substrate and maintained more flexed limbs and posterior hand positions compared with the kinematics of running. As a result, climbers differed significantly from both the running and control mice in developing a relatively broader infraspinous region, which is likely related to preferential recruitment of the infraspinatus and teres minor muscles to maintain flexed shoulder postures. The results of this study demonstrate that variation in activity level and type of locomotor regime over a significant portion of the life history influences muscle and bone development in the shoulder. Copyright © 2012 Wiley Periodicals, Inc.

  7. Creep mechanisms and constitutive relations in pure metals

    International Nuclear Information System (INIS)

    Nix, W.D.

    1979-01-01

    The mechanisms of creep of pure metals is briefly reviewed and divided into two parts: steady state flow mechanisms, and non-steady state flow mechanisms and constitutive relations. Creep by diffusional flow is now reasonably well understood, with theory and experiment in good agreement. The closely related phenomenon of Harper--Dorn creep can also be understood in terms of diffusion between dislocations. Power law creep involves the climb of edge disloctions controlled by lattice self diffusion. Theoretical treatments of this process invariably give a power law exponent of 3. This natural creep law is compared with the data for FCC and BCC metals. It is suggested that diffusion controlled climb is the controlling process in BCC metals at very high temperatures. Stacking fault energy effects may preclude the possibility that creep is controlled entirely by lattice self diffusion in some FCC metals. The subject of power law breakdown is presented as a natural consequence of the transition to low temperature flow phenomena. The role of core diffusion in this transition is briefly discussed. The mechanisms are presented by which pure metals creep at elevated temperatures. While most of this review deals with the mechanisms of steady state flow, some discussion is devoted to creep flow under non-steady state conditions. This topic is discussed in connection with the development of constitutive equations for describing plastic flow in metals

  8. Wa-Chair: A concept for development of economical stair-climbing wheelchair

    Science.gov (United States)

    Jyoti Baishya, Nayan; Ogai, Harutoshi

    2018-02-01

    In this paper, a concept for development of cost effective and reliable stair climbing wheelchair is being proposed. Slider-crank mechanism is being used to compensate for any variation in inclination angle of the wheelchair during ascent or descent on stairs. Controlling wheelchair’s inclination angle can reduce risk for the rider as it prevents the wheelchair from toppling. A prototype is being developed to validate proposed mechanism. Proposed mechanism allows rider to view in the direction of progress which adds additional safety to the rider.

  9. Dislocation Nucleation on Grain Boundaries: Low Angle Twist and Asymmetric Tilt Boundaries

    Directory of Open Access Journals (Sweden)

    Erman Guleryuz

    2016-07-01

    Full Text Available We investigate the mechanisms of incipient plasticity at low angle twist and asymmetric tilt boundaries in fcc metals. To observe plasticity of grain boundaries independently of the bulk plasticity, we simulate nanoindentation of bicrystals. On the low angle twist boundaries, the intrinsic grain boundary (GB dislocation network deforms under load until a dislocation segment compatible with glide on a lattice slip plane is created. The half loops are then emitted into the bulk of the crystal. Asymmetric twist boundaries considered here did not produce bulk dislocations under load. Instead, the boundary with a low excess volume nucleated a mobile GB dislocation and additional GB defects. The GB sliding proceeded by motion of the mobile GB dislocation. The boundary with a high excess volume sheared elastically, while bulk-nucleated dislocations produced plastic relaxation.

  10. Reduction of threading dislocation density in SiGe epilayer on Si (0 0 1) by lateral growth liquid-phase epitaxy

    Science.gov (United States)

    O'Reilly, Andrew J.; Quitoriano, Nathaniel J.

    2018-02-01

    Si0.973Ge0.027 epilayers were grown on a Si (0 0 1) substrate by a lateral liquid-phase epitaxy (LLPE) technique. The lateral growth mechanism favoured the glide of misfit dislocations and inhibited the nucleation of new dislocations by maintaining the thickness less than the critical thicknesses for dislocation nucleation and greater than the critical thickness for glide. This promoted the formation of an array of long misfit dislocations parallel to the [1 1 0] growth direction and reduced the threading dislocation density to 103 cm-2, two orders of magnitude lower than the seed area with an isotropic misfit dislocation network.

  11. Dislocation dynamics simulations of plasticity at small scales

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Caizhi [Iowa State Univ., Ames, IA (United States)

    2010-01-01

    As metallic structures and devices are being created on a dimension comparable to the length scales of the underlying dislocation microstructures, the mechanical properties of them change drastically. Since such small structures are increasingly common in modern technologies, there is an emergent need to understand the critical roles of elasticity, plasticity, and fracture in small structures. Dislocation dynamics (DD) simulations, in which the dislocations are the simulated entities, offer a way to extend length scales beyond those of atomistic simulations and the results from DD simulations can be directly compared with the micromechanical tests. The primary objective of this research is to use 3-D DD simulations to study the plastic deformation of nano- and micro-scale materials and understand the correlation between dislocation motion, interactions and the mechanical response. Specifically, to identify what critical events (i.e., dislocation multiplication, cross-slip, storage, nucleation, junction and dipole formation, pinning etc.) determine the deformation response and how these change from bulk behavior as the system decreases in size and correlate and improve our current knowledge of bulk plasticity with the knowledge gained from the direct observations of small-scale plasticity. Our simulation results on single crystal micropillars and polycrystalline thin films can march the experiment results well and capture the essential features in small-scale plasticity. Furthermore, several simple and accurate models have been developed following our simulation results and can reasonably predict the plastic behavior of small scale materials.

  12. Determination of the extinction factor in function of the density of dislocations

    International Nuclear Information System (INIS)

    Macias B, L.R.

    1991-12-01

    There are exist three basic types of crystalline lattice defects: point, line (or dislocations) and surface defects. Such defects may be incorporated intentionally to produce desired mechanical and physical properties. This report presents a FORTRAN language program to calculate the extinction factor in samples of polycrystalline copper as function of the dislocations density. (Author)

  13. Nerve lesions associated with shoulder dislocation; an electrodiagnostic study of 11 cases.

    OpenAIRE

    Liveson, J A

    1984-01-01

    Electrodiagnostic examination of 11 patients with shoulder dislocation revealed nerve damage not previously reported. Although axillary nerve lesions were most common, posterior cord and musculocutaneous nerve damage occurred each in five cases. The mechanism of injury was important. The most surprising patterns were associated with blunt injury or recurrent spontaneous dislocation.

  14. Acute traumatic anterior glenohumeral dislocation complicated by axillary nerve damage: a case report

    OpenAIRE

    Kazemi, Mohsen

    1998-01-01

    An elite soccer player presented with a classic acute anterior dislocation of the glenohumeral joint complicated by axillary nerve damage. The incidence, mechanism of injury, clinical presentation, conservative treatment and rehabilitation of the anterior glenohumeral joint dislocation and associated axillary nerve damage are discussed in this paper.

  15. On the multiplication of dislocations during martensitic transformations in NiTi shape memory alloys

    Czech Academy of Sciences Publication Activity Database

    Simon, T.; Kröger, A.; Somsen, Ch.; Dlouhý, Antonín; Eggeler, G.

    2010-01-01

    Roč. 58, č. 5 (2010), s. 1850-1860 ISSN 1359-6454 R&D Projects: GA ČR GA106/09/1913 Institutional research plan: CEZ:AV0Z20410507 Keywords : NiTi * Martensitic transformations * Dislocation multiplication mechanism * Martensite variants * Dislocations Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.781, year: 2010

  16. Anterior superior dislocation of the hip joint: A report of 3 cases and ...

    African Journals Online (AJOL)

    ... resembles that of posterior hip dislocation. The objective of this article is to use three cases to describe the management of this condition and highlight pitfalls in the same. The article also points out unusual mechanisms causing this injury. Key words: Anterior dislocation, Hip joint, Open reduction, Iliofemoral ligament ...

  17. Observations of Glide and Decomposition of a Dislocations at High Temperatures in Ni-Al Single Crystals Deformed along the Hard Orientation

    Science.gov (United States)

    Srinivasan, R.; Daw, M. S.; Noebe, R. D.; Mills, M. J.

    2003-01-01

    Ni-44at.% Al and Ni-50at.% single crystals were tested in compression in the hard (001) orientations. The dislocation processes and deformation behavior were studied as a function of temperature, strain and strain rate. A slip transition in NiAl occurs from alpha(111) slip to non-alphaaaaaaaaaaa9111) slip at intermediate temperatures. In Ni-50at.% Al single crystal, only alpha(010) dislocations are observed above the slip transition temperature. In contrast, alpha(101)(101) glide has been observed to control deformation beyond the slip transition temperature in Ni-44at.%Al. alpha(101) dislocations are observed primarily along both (111) directions in the glide plane. High-resolution transmission electron microscopy observations show that the core of the alpha(101) dislocations along these directions is decomposed into two alpha(010) dislocations, separated by a distance of approximately 2nm. The temperature window of stability for these alpha(101) dislocations depends upon the strain rate. At a strain rate of 1.4 x 10(exp -4)/s, lpha(101) dislocations are observed between 800 and 1000K. Complete decomposition of a alpha(101) dislocations into alpha(010) dislocations occurs beyond 1000K, leading to alpha(010) climb as the deformation mode at higher temperature. At lower strain rates, decomposition of a alpha(101) dislocations has been observed to occur along the edge orientation at temperatures below 1000K. Embedded-atom method calculations and experimental results indicate that alpha(101) dislocation have a large Peieris stress at low temperature. Based on the present microstructural observations and a survey of the literature with respect to vacancy content and diffusion in NiAl, a model is proposed for alpha(101)(101) glide in Ni-44at.%Al, and for the observed yield strength versus temperature behavior of Ni-Al alloys at intermediate and high temperatures.

  18. Video Analysis of Primary Shoulder Dislocations in Rugby Tackles.

    Science.gov (United States)

    Maki, Nobukazu; Kawasaki, Takayuki; Mochizuki, Tomoyuki; Ota, Chihiro; Yoneda, Takeshi; Urayama, Shingo; Kaneko, Kazuo

    2017-06-01

    Characteristics of rugby tackles that lead to primary anterior shoulder dislocation remain unclear. To clarify the characteristics of tackling that lead to shoulder dislocation and to assess the correlation between the mechanism of injury and morphological damage of the glenoid. Case series; Level of evidence, 4. Eleven elite rugby players who sustained primary anterior shoulder dislocation due to one-on-one tackling between 2001 and 2014 were included. Using an assessment system, the tackler's movement, posture, and shoulder and head position were evaluated in each phase of tackling. Based on 3-dimensional computed tomography, the glenoid of the affected shoulder was classified into 3 types: intact, erosion, and bone defect. Orientation of the glenoid defect and presence of Hill-Sachs lesion were also evaluated. Eleven tackles that led to primary shoulder dislocation were divided into hand, arm, and shoulder tackle types based on the site at which the tackler contacted the ball carrier initially. In hand and arm tackles, the tackler's shoulder joint was forcibly moved to horizontal abduction by the impact of his upper limb, which appeared to result from an inappropriate approach to the ball carrier. In shoulder tackles, the tackler's head was lowered and was in front of the ball carrier at impact. There was no significant correlation between tackle types and the characteristics of bony lesions of the shoulder. Although the precise mechanism of primary anterior shoulder dislocation could not be estimated from this single-view analysis, failure of individual tackling leading to injury is not uniform and can be caused by 2 main factors: failure of approach followed by an extended arm position or inappropriate posture of the tackler at impact, such as a lowered head in front of the opponent. These findings indicate that injury mechanisms should be assessed for each type of tackle, as it is unknown whether external force to the glenoid is different in each mechanism

  19. The acute toxicity of the metaldehyde on the climbing perch

    Science.gov (United States)

    Wahida Mohamad Ismail, Syamimi; Aini Dahalan, Farrah; Zakaria, Ammar; Mad Shakaff, Ali Yeon; Aqlima Ahmad, Siti; Shukor, Mohd Yunus Abd; Khalizan Sabullah, Mohd; Khalil, Khalilah Abdul; Jalil, Mohd Faizal Ab

    2018-03-01

    In Asia, Climbing perch (Anabas testudineus) is commonly found in paddy fields and irrigation systems. Due to its habitat, Climbing perch is exposed to toxic pesticides used in paddy fields such as metaldehyde which is one of the most widely used molluscicide. This study aims to determine the acute toxicity Lethal Concentration50 (LC50) of metaldehyde and its effect on the behaviour and physical changes of the Climbing perch. The fish mortality responses to six different metaldehyde concentrations ranging from 180 to 330 mg/L were investigated. The 96-h LC50 values were determined and analysed using three different analysis methods which is arithmetic, logarithmic and probit graphic. The LC50 values obtained in this study were 239, 234 and 232 mg/L, respectively. After 96-h of exposure to metaldehyde, the fish showed a series of abnormal behavioural response in all cases: imbalance position, and restlessness of movement. The LC50 values show that metaldehyde is moderately toxic to the Climbing perch indicating that metaldehyde is not destructive to Climbing perch. However, long term exposure of aquatic organisms to the metaldehyde means a continuous health risk for the fish population as they are more vulnerable and it is on high risk for human to consume this toxicated fishes.

  20. Therapeutic use of sport climbing for patients with multiple sclerosis

    Directory of Open Access Journals (Sweden)

    Ana Ožura

    2009-05-01

    Full Text Available Sport climbing is a form of exercise that requires complex and variable movement. Because of the use of the so-called "top-rope system", this is a safe activity appropriate for individuals with physical disabilities. Therefore, climbing might prove to be an effective form of therapy for patients with multiple sclerosis. Multiple sclerosis is a chronic neurological disease that may include motor and cognitive deficits as well as affective disturbances. The illness is characterized by multifocal areas of brain damage (plaques, as consequence of autoimmune inflammation. Sport climbing might be a potentially useful activity for treating spasticity, improving a person's self image and certain aspects of cognition, such as attention and executive functions, as well as for managing emotional disturbances. All of the above are areas where patients with multiple sclerosis might be in need of assistance. The article also describes the experience of a patient with multiple sclerosis who was enrolled in our climbing program. Future research is needed to evaluate the effect of climbing therapy for patients with multiple sclerosis.

  1. High temperature dislocation processes in precipitation hardened crystals investigated by a 3D discrete dislocation dynamics

    Czech Academy of Sciences Publication Activity Database

    Záležák, Tomáš; Svoboda, Jiří; Dlouhý, Antonín

    2017-01-01

    Roč. 97, OCT (2017), s. 1-23 ISSN 0749-6419 R&D Projects: GA ČR(CZ) GA14-22834S; GA ČR(CZ) GA202/09/2073; GA ČR(CZ) GD106/09/H035; GA MŠk(CZ) EE2.3.20.0214; GA MŠk OC 162 EU Projects: European Commission(XE) 309916 - Z-ULTRA Institutional support: RVO:68081723 Keywords : 3D discrete dislocation dynamics * Dislocations * Strengthening mechanisms * Low angle grain boundaries * Particulate reinforced material Subject RIV: JI - Composite Materials OBOR OECD: Composites (including laminates, reinforced plastics, cermets, combined natural and synthetic fibre fabrics Impact factor: 5.702, year: 2016

  2. Irreducible Traumatic Posterior Shoulder Dislocation

    Directory of Open Access Journals (Sweden)

    Blake Collier

    2017-01-01

    Full Text Available History of present illness: A 22-year-old male presented to the Emergency Department complaining of right shoulder pain after a motocross accident. He was traveling at approximately 10 mph around a turn when he lost control and was thrown over the handlebars, landing directly on his right shoulder. On arrival, he was holding his arm in adduction and internal rotation. An area of swelling was noted over his anterior shoulder. He was unable to abduct his shoulder. No humeral gapping was noted. He had normal neuro-vascular status distal to the injury. Significant findings: Radiographs demonstrated posterior displacement of the humeral head on the “Y” view (see white arrow and widening of the glenohumeral joint space on anterior-posterior view (see red arrow. The findings were consistent with posterior dislocation and a Hill-Sachs type deformity. Sedation was performed and reduction was attempted using external rotation, traction counter-traction. An immediate “pop” was felt during the procedure. Post-procedure radiographs revealed a persistent posterior subluxation with interlocking at posterior glenoid. CT revealed posterior dislocation with acute depressed impaction deformity medial to the biceps groove with the humeral head perched on the posterior glenoid, interlocked at reverse Hill-Sachs deformity (see blue arrow. Discussion: Posterior shoulder dislocations are rare and represent only 2% of all shoulder dislocations. Posterior shoulder dislocations are missed on initial diagnosis in more than 60% of cases.1 Posterior shoulder dislocations result from axial loading of the adducted and internally rotated shoulder, violent muscle contractions (resulting from seizures or electrocution, a direct posterior force applied to the anterior shoulder.1 Physical findings include decreased anterior prominence of the humeral head, increased palpable posterior prominence of the humeral head below the acromion, increased palpable prominence of the

  3. Reactions between a 1/2⟨111⟩ screw dislocation and ⟨100⟩ interstitial dislocation loops in alpha-iron modelled at atomic scale

    Science.gov (United States)

    Terentyev, D.; Bacon, D. J.; Osetsky, Yu. N.

    2010-03-01

    Interstitial dislocation loops with Burgers vector of ? type are observed in α-iron irradiated by neutrons or heavy ions, and their population increases with increasing temperature. Their effect on motion of a ? edge dislocation was reported earlier 1. Results are presented of a molecular dynamics study of interactions between a ? screw dislocation and ? loops in iron at temperature in the range 100 to 600 K. A variety of reaction mechanisms and outcomes are observed and classified in terms of the resulting dislocation configuration and the maximum stress required for the dislocation to break away. The highest obstacle resistance arises when the loop is absorbed to form a helical turn on the screw dislocation line, for the dislocation cannot glide away until the turn closes and a loop is released with the same Burgers vector as the line. Other than one situation found, in which no dislocation-loop reaction occurs, the weakest obstacle strength is found when the original ? loop is restored at the end of the reaction. The important role of the cross-slip and the influence of model boundary conditions are emphasised and demonstrated by examples.

  4. In situ transmission electron microscopy observation of dislocation motion in 9Cr steel at elevated temperatures: influence of shear stress on dislocation behavior.

    Science.gov (United States)

    Yamada, Susumu; Sakai, Takayuki

    2014-12-01

    To elucidate high-temperature plastic deformation (creep) mechanism in materials, it is essential to observe dislocation motion under tensile loading. There are many reports on in situ transmission electron microscopy (TEM) observations in the literature; however, the relationship between the dislocation motion and shear stress in 9Cr steel is still not clear. In this study, in order to evaluate this relationship quantitatively, in situ TEM observations were carried out in conjunction with finite element method (FEM) analysis. A tensile test sample was strained at an elevated temperature (903 K) inside a transmission electron microscope, and the stress distribution in the strained sample was analyzed by FEM. The dislocation behavior was clearly found to depend on the shear stress. At a shear stress of 66 MPa, both the dislocation velocity and mobile dislocation density were low. However, a high shear stress level of 95 MPa caused a noticeable increase in the dislocation velocity and mobile dislocation density. Furthermore, in this article, we discuss the dependence of the dislocation behavior on stress. The results presented here also indicate that the relationship between the microstructure and the strength of materials can be revealed by the methods used in this work. © The Author 2014. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  5. The movement of screw dislocations in tungsten

    Energy Technology Data Exchange (ETDEWEB)

    Tian Xiaogeng; Woo Chungho

    2004-03-25

    Using Acland potential for tungsten, the movement of 1/2a<1 1 1> screw dislocation under shear stress was investigated by molecular dynamics simulation. Equilibrated core structure was obtained by relaxation of screw dislocation with proper boundary conditions. We found that the equilibrium dislocation core has three-fold symmetry and spread out in three <1 1 2> direction on {l_brace}1 1 0{r_brace} planes. The screw dislocation core could not keep the original shape when the shear stress applied. The dislocation could not move until the shear stress became large enough. The dislocation moved in zigzag when the shear stress neared the Peierls stress. When the shear stress became larger, the dislocation moved in zigzag at the beginning and than moved almost in straight line in [2-bar11] direction. The large shear stress applied, the long distance moved before the dislocation stilled in z-direction and the large velocity in y-direction.

  6. Modification of a Limbed Robot to Favor Climbing

    Science.gov (United States)

    Okon, Avi; Kennedy, Brett; Garrett, Michael; Magnone, Lee

    2006-01-01

    The figure shows the LEMUR IIb, which is a modified version of the LEMUR II the second generation of the Limbed Excursion Mechanical Utility Robot (LEMUR). Except as described below, the LEMUR IIb hardware is mostly the same as that of the LEMUR II. The IIb and II versions differ in their kinematic configurations and characteristics associated with their kinematic configurations. The differences are such that relative to the LEMUR II, the LEMUR IIb is simpler and is better suited to climbing on inclined surfaces. The first-generation LEMUR, now denoted the LEMUR I, was described in Six-Legged Experimental Robot (NPO-20897), NASA Tech Briefs, Vol. 25, No. 12 (December 2001), page 58. The LEMUR II was described in Second-Generation Six-Limbed Experimental Robot (NPO-35140) NASA Tech Briefs, Vol. 28, No. 11 (November 2004), page 55. To recapitulate: the LEMUR I and LEMUR II were six-legged or sixlimbed robots for demonstrating robotic capabilities for assembly, maintenance, and inspection. They were designed to be capable of walking autonomously along a truss structure toward a mechanical assembly at a prescribed location. They were equipped with stereoscopic video cameras and image-data-processing circuitry for navigation and mechanical operations. They were also equipped with wireless modems, through which they could be commanded remotely. Upon arrival at a mechanical assembly, the LEMUR I would perform simple mechanical operations by use of one or both of its front legs (or in the case of the LEMUR II, any of its limbs could be used to perform mechanical operations). Either LEMUR could also transmit images to a host computer. The differences between the LEMUR IIb and the LEMUR II are the following: Whereas the LEMUR II had six limbs, the LEMUR IIb has four limbs. This change has reduced both the complexity and mass of the legs and of the overall robot. Whereas each limb of the LEMUR II had four degrees of freedom (DOFs), each limb of the LEMUR IIb has three DOFs

  7. Atomistic simulations of dislocation processes in copper

    DEFF Research Database (Denmark)

    Vegge, T.; Jacobsen, K.W.

    2002-01-01

    We discuss atomistic simulations of dislocation processes in copper based on effective medium theory interatomic potentials. Results on screw dislocation structures and processes are reviewed with particular focus on point defect mobilities and processes involving cross slip. For example, the sta......We discuss atomistic simulations of dislocation processes in copper based on effective medium theory interatomic potentials. Results on screw dislocation structures and processes are reviewed with particular focus on point defect mobilities and processes involving cross slip. For example...

  8. Microstructure, quantification and control of dislocations in bast-type plant fibres

    DEFF Research Database (Denmark)

    Madsen, Bo; Lester, Catherine L.; Mortensen, Ulrich Andreas

    2016-01-01

    analysis is presented for the quantification of dislocations in plant fibres. The protocol is evaluated with respect to its robustness, and the uncertainty of the determined content of dislocations. Based on in-situ straining of fibres under the optical microscopy, findings are presented to show......Bast-type plant fibres are increasingly being used for structural composite applications where high quality fibres with good mechanical properties are required. A central aspect for this application is the existence of dislocations in the cell wall of plant fibres, i.e. regions of misaligned...... that this leads to a reduction in the content of dislocations. This is indicating that dislocations in the cell wall of plant fibres are changeable structures. Preliminary work is presented where plant fibres are exposed to physical treatments involving moisture and mechanical straining in order to change...

  9. Single crystal plasticity by modeling dislocation density rate behavior

    Energy Technology Data Exchange (ETDEWEB)

    Hansen, Benjamin L [Los Alamos National Laboratory; Bronkhorst, Curt [Los Alamos National Laboratory; Beyerlein, Irene [Los Alamos National Laboratory; Cerreta, E. K. [Los Alamos National Laboratory; Dennis-Koller, Darcie [Los Alamos National Laboratory

    2010-12-23

    The goal of this work is to formulate a constitutive model for the deformation of metals over a wide range of strain rates. Damage and failure of materials frequently occurs at a variety of deformation rates within the same sample. The present state of the art in single crystal constitutive models relies on thermally-activated models which are believed to become less reliable for problems exceeding strain rates of 10{sup 4} s{sup -1}. This talk presents work in which we extend the applicability of the single crystal model to the strain rate region where dislocation drag is believed to dominate. The elastic model includes effects from volumetric change and pressure sensitive moduli. The plastic model transitions from the low-rate thermally-activated regime to the high-rate drag dominated regime. The direct use of dislocation density as a state parameter gives a measurable physical mechanism to strain hardening. Dislocation densities are separated according to type and given a systematic set of interactions rates adaptable by type. The form of the constitutive model is motivated by previously published dislocation dynamics work which articulated important behaviors unique to high-rate response in fcc systems. The proposed material model incorporates thermal coupling. The hardening model tracks the varying dislocation population with respect to each slip plane and computes the slip resistance based on those values. Comparisons can be made between the responses of single crystals and polycrystals at a variety of strain rates. The material model is fit to copper.

  10. 3D quantum liquid crystals by condensation of dislocation worldsheets

    Science.gov (United States)

    Beekman, Aron; Wu, Kai; Nissinen, Jaakko; Zaanen, Jan

    A solid can partially melt into a liquid crystal where rotational rigidity is maintained while translational symmetry is restored. The topological melting is caused by an unbinding of dislocations. We recently provided a comprehensive review of quantum dislocation-mediated melting in 2D (arXiv:1603.04254). Through a duality mapping, phonons turn into dual gauge fields mediating interactions between dislocations. Upon condensation of dislocations, the dual gauge fields undergo the Anderson-Higgs mechanism and become gapped, signaling the loss of shear rigidity. Here we extend this theory to three dimensions. Dislocations are now linelike objects, strings, tracing out worldsheets in spacetime, while the dual gauge-fields become two-form (Kalb-Ramond) fields. We obtain the Higgs phase of these two-form gauge fields. Translational symmetry can be restored in three, two or one directions leading to nematic, smectic or columnar quantum liquid crystals. We derive the spectrum of low-energy excitations and its linear response. Goldstone modes due to broken rotational symmetry as well as superconductivity emerge whenever translational symmetry is restored. The peculiar features of liquid-crystalline order can be probed by finite-momentum spectroscopy.

  11. Effect of alcohol on performance in sport climbing

    OpenAIRE

    Šafránek, Vojtěch

    2011-01-01

    Name of thesis: The effect of alcohol on performance in sport climbing Abstract: The goals: The aim of this thesis is to assess the influence of alcohol on performance in sport climbing. Methods: There were six climbers (4 men a 2 women) with average age 24,8±4,5 in this study. Before the test, the first group of climbers had to drink fruit juice mixed with 0,6 ml of 100% alcohol per 1 kg of their body weight, or the fruit juice itself. 60 minutes after ingestion of alcoholic or nonalcoholic ...

  12. Dislocation unpinning model of acoustic emission from alkali halide ...

    Indian Academy of Sciences (India)

    theoretical and experimental results related to the AE from alkali halide crystals. Keywords. Acoustic emission; dislocation; alkali halide crystals; plastic deformation. PACS Nos 43.40.Le; 62.20.Fe; 61.72.Hh. 1. Introduction. Discrete acoustic wave packets are generated in solids during their mechanical de- formation.

  13. Atlantooccipital dislocation: a case report.

    Science.gov (United States)

    Williams, M J; Elliott, J L; Nichols, J

    1995-03-01

    We report on a child who suffered an atlantooccipital dislocation and survived. The patient required tracheostomy and feeding gastrostomy due to retropharyngeal swelling from a traumatic pseudomeningocele. He later underwent fusion of his occiput to C3. The complications of such an injury and the anesthetic management are discussed.

  14. Lateral atlantooccipital dislocation: case report.

    Science.gov (United States)

    Watridge, C B; Orrison, W W; Arnold, H; Woods, G A

    1985-08-01

    A case of lateral atlantooccipital dislocation is presented, and its successful management is outlined, demonstrating the importance of the physical examination and the utilization of computed tomography. Open reduction and stabilization with direct visualization of the spinal axis is the preferred method of treatment.

  15. Medial peritalar fracture dislocation of the talar body

    Directory of Open Access Journals (Sweden)

    Jacob B. Stirton

    2015-04-01

    Full Text Available Peritalar fracture dislocations typically involve the talar neck and are classified according to Hawkins. To our knowledge, peritalar fracture dislocation involving the talar body has not been formally reported. In this article, we describe a case of peritalar fracture dislocation of the talar body. Keywords: Peritalar dislocation, Talus fracture, Talar body fracture dislocation, Medial subtalar dislocation

  16. Epitaxial strain relaxation by provoking edge dislocation dipoles

    Science.gov (United States)

    Soufi, A.; El-Hami, K.

    2018-02-01

    Thin solid films have been used in various devices and engineering systems such as rapid development of highly integrated electronic circuits, the use of surface coatings to protect structural materials in high temperature environments, and thin films are integral parts of many micro-electro-mechanical systems designed to serve as sensors, actuators. Among techniques of ultra-thin films deposition, the heteroepitaxial method becomes the most useful at nanoscale level to obtain performed materials in various applications areas. On the other hand, stresses that appeared during the elaboration of thin films could rise deformations and fractures in materials. The key solution to solve this problem at the nanoscale level is the nucleation of interface dislocations from free surfaces. By provoking edge dislocation dipoles we obtained a strain relaxation in thin films. Moreover, the dynamic of nucleation in edge dislocations from free lateral surfaces was also studied.

  17. Dislocation mediated alignment during metal nanoparticle coalescence

    International Nuclear Information System (INIS)

    Lange, A.P.; Samanta, A.; Majidi, H.; Mahajan, S.; Ging, J.; Olson, T.Y.; Benthem, K. van; Elhadj, S.

    2016-01-01

    Dislocation mediated alignment processes during gold nanoparticle coalescence were studied at low and high temperatures using molecular dynamics simulations and transmission electron microscopy. Particles underwent rigid body rotations immediately following attachment in both low temperature (500 K) simulated coalescence events and low temperature (∼315 K) transmission electron microscopy beam heating experiments. In many low temperature simulations, some degree of misorientation between particles remained after rigid body rotations, which was accommodated by grain boundary dislocation nodes. These dislocations were either sessile and remained at the interface for the duration of the simulation or dissociated and cross-slipped through the adjacent particles, leading to improved co-alignment. Minimal rigid body rotations were observed during or immediately following attachment in high temperature (1100 K) simulations, which is attributed to enhanced diffusion at the particles' interface. However, rotation was eventually induced by {111} slip on planes parallel to the neck groove. These deformation modes led to the formation of single and multi-fold twins whose structures depended on the initial orientation of the particles. The driving force for {111} slip is attributed to high surface stresses near the intersection of low energy {111} facets in the neck region. The details of this twinning process were examined in detail using simulated trajectories, and the results reveal possible mechanisms for the nucleation and propagation of Shockley partials on consecutive planes. Deformation twinning was also observed in-situ using transmission electron microscopy, which resulted in the co-alignment of a set of the particles' {111} planes across their grain boundary and an increase in their dihedral angle. This constitutes the first detailed experimental observation of deformation twinning during nanoparticle coalescence, validating simulation results

  18. Medial subtalar dislocation: Case report

    Directory of Open Access Journals (Sweden)

    Manojlović Radovan

    2010-01-01

    Full Text Available Introduction. Subtalar dislocation (SI is a term that refers to an injury in which there is dislocation of the talonavicular and talocalcanear joint, although the tibiotalar joint is intact. Case Outline. A case of medial subtalar dislocation as a result of basketball injury, so-called 'basketball foot', is presented. Closed reposition in i.v. anaesthesia was performed with the patient in supine position and a knee flexed at 90 degrees. Longitudinal manual traction in line of deformity was carried out in plantar flexion. The reposition continued with abduction and eversion simultaneously increasing dorsiflexion. It was made in the first attempt and completed instantly. Rehabilitation was initiated after 5 weeks of immobilization. One year after the injury, the functional outcome was excellent with full range of motion and the patient was symptom-free. For better interpretation of roentgenogram, bone model of subtalar dislocation was made using the cadaver bone. Conclusion. Although the treatment of such injury is usually successful, diagnosis can be difficult because it is a rare injury, and moreover, X-ray of the injury can be confusing due to superposition of bones. Radiograms revealed superposition of the calcaneus, tarsal and metatarsal bones which was radiographically visualized in the anterior-posterior projection as one osseous block inward from the talus, and on the lateral view as in an osteal block below the tibial bone. Prompt recognition of these injuries followed by proper, delicately closed reduction under anaesthesia is crucial for achieving a good functional result in case of medial subtalar dislocation.

  19. Bilateral Traumatic Anterior Dislocation of Shoulder – a rare entity

    Directory of Open Access Journals (Sweden)

    Yashavantha Kumar C

    2013-01-01

    Full Text Available Introduction: Bilateral shoulder dislocation are most commonly posterior type. These are most commonly due to seizure disorder and electrocution. Anterior shoulder dislocations occurring bilaterally without any predisposing factors are very rare. These types of injuries are due to trauma with a unique mechanism of injury. To best of our knowledge there are only few cases of similar kind are reported in literature. We hereby report a interesting case of posttraumatic, bilateral anterior dislocation of shoulder without associated fracture in a 45 old women without any predisposing pathoanatomy.Case Report: A 45-year-old women presented to casualty with sudden onset of pain and restriction of movement in both shoulders fallowing trauma. Immediately post trauma she had severe pain and restriction of both shoulders. On examination arms were abducted and externally rotated. Bilateral shoulder movements were painful and restricted . There was loss of round contour of shoulder with increased vertical diameter of axilla anteriorly. Radiological examination revealed bilateral anterior dislocation of the shoulders without any associated fractures. Closed reduction done by Milch technique after intraraticular lignocaine injection. MRI of bilateral shoulder showed no pathological lesion. Both shoulders were immobilized with a shoulder immobilizer for three weeks.Conclusion: Most of the bilateral shoulder dislocations are posterior type seen in seizure disorders. Bilateral traumatic anterior shoulder dislocations are rare and are seen as a result of unique mechanism of injury. In our case patient had a fall on her elbows causing forced extension. If diagnosed and treated promptly completely normal function of the shoulders can be restored.

  20. Dislocations and vacancies in two-dimensional mixed crystals of spheres and dimers

    KAUST Repository

    Gerbode, Sharon J.

    2010-10-15

    In colloidal crystals of spheres, dislocation motion is unrestricted. On the other hand, recent studies of relaxation in crystals of colloidal dimer particles have demonstrated that the dislocation dynamics in such crystals are reminiscent of glassy systems. The observed glassy dynamics arise as a result of dislocation cages formed by certain dimer orientations. In the current study, we use experiments and simulations to investigate the transition that arises when a pure sphere crystal is doped with an increasing concentration of dimers. Specifically, we focus on both dislocation caging and vacancy motion. Interestingly, we find that any nonzero fraction of dimers introduces finite dislocation cages, suggesting that glassy dynamics are present for any mixed crystal. However, we have also identified a vacancy-mediated uncaging mechanism for releasing dislocations from their cages. This mechanism is dependent on vacancy diffusion, which slows by orders of magnitude as the dimer concentration is increased. We propose that in mixed crystals with low dimer concentrations vacancy diffusion is fast enough to uncage dislocations and delay the onset of glassy dislocation dynamics. © 2010 The American Physical Society.

  1. Posterior sternoclavicular dislocation: A case report

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, So Hwa; Kim, Ki Sun; Kim, Ki Jun [Dept. of Radiology, Incheon St. Mary' s Hospital, The Catholic University of Korea College of Medicine, Incheon (Korea, Republic of)

    2015-02-15

    Traumatic sternoclavicular joint dislocation is an uncommon injury, and posterior sternoclavicular dislocation occurs less frequently compared to anterior sternoclavicular dislocation. However, this type of dislocation has the potential for serious complications due to compression or laceration of the mediastinal structures. The diagnosis can be difficult using plain radiographs alone due to radiographic-anatomic superimposition. Therefore, posterior sternoclavicular dislocation is easily missed at the initial clinical evaluation. Contrast-enhanced computed tomography is required for a definite diagnosis and to assess associated mediastinal injuries.

  2. Application of Nadal Limit in the prediction of wheel climb derailment

    Science.gov (United States)

    2011-03-16

    Application of the Nadal Limit to the prediction of wheel climb derailment is presented along with the effect of pertinent geometric and material parameters. Conditions which : contribute to this climb include wheelset angle of attack, contact angle,...

  3. Acute, recurrent total knee dislocation: Polyethylene dislocation and malreduction

    Directory of Open Access Journals (Sweden)

    Samuel F. Thompson, BS

    2015-03-01

    Full Text Available A 62-year-old man underwent total knee arthroplasty using a mobile-bearing prosthesis. Four days post-operatively the patient experienced the first of several acute knee dislocations. Closed reduction was performed at an outside hospital a total of three times prior to presentation at this institution. A two-stage exchange of the TKA was recommended due to the clinical suspicion for an infected prosthesis. Upon surgical exploration, it was discovered that the polyethylene insert had spun out completely to 180°. Closed reduction attempts of a posterior dislocation of a mobile-bearing knee prosthesis may contribute to complete 180° spinout of the polyethylene insert.

  4. Piper (Piperaceae) in the Solomon Islands: the climbing species

    NARCIS (Netherlands)

    Gardner, R.O.

    2010-01-01

    Eleven climbing species of Piper in the Solomon Islands are recognized: P. abbreviatum, P. betle, P. bosnicanum, P. caninum, P. celtidiforme, P. fragile, P. insectifugum (syn. P. austrocaledonicum), P. interruptum, P. macropiper, P. majusculum, and, as the only endemic, P. sclerophloeum, for which a

  5. Agronomic description of new improved climbing bean varieties

    African Journals Online (AJOL)

    . 21. David, S and Hoogendijk,M. 1997. Bean production systems in MbaJe district, Uganda with emphasis on varietal diversity and the adoption of new climbing beans. Network on bean research in Africa. CIA T. CIA T, occasional publication ...

  6. Climbing Mount Everest: on our way to the summit.

    Science.gov (United States)

    Shamian, Judith

    2003-01-01

    The key to climbing Mount Everest is not one individual striving for the peak. Teamwork, leadership, and meticulous planning are what take climbers to the summit. They are key, as well, to solving the problems of human resources in the healthcare system.

  7. relative performance of staking techniques on yield of climbing bean

    African Journals Online (AJOL)

    ACSS

    Common bean (Phaseolus vulgaris L.) is an important staple grain legume in the Great Lakes Region of Africa. In addition, it is a major source of proteins, energy and micro-nutrients (e.g. Fe and Zn), especially for smallholder farmers. The climbing bean is particularly more productive, an efficient land user and tolerant to ...

  8. Full-body movement pattern recognition in climbing*

    NARCIS (Netherlands)

    Seifert, Ludovic; Dovgalecs, Vladislavs; Boulanger, Jérémie; Orth, Dominic; Hérault, Romain; Davids, Keith

    2014-01-01

    The aim of this study was to propose a method for full-body movement pattern recognition in climbing, by computing the 3D unitary vector of the four limbs and pelvis during performance. One climber with an intermediate skill level traversed two easy routes of similar rates of difficulty (5c

  9. Hold design supports learning and transfer of climbing fluency

    NARCIS (Netherlands)

    Orth, Dominic; Davids, Keith; Seifert, Ludovic

    2014-01-01

    Being a discipline with a broad range of genres, rock climbing is an activity where participants seek to generalize the skills they learn in different performance contexts. A training strategy for achieving skill transfer was explored in a group of experienced climbers. Specifically, we tested the

  10. Nutrient composition of climbing and prostrate vegetable cowpea ...

    African Journals Online (AJOL)

    The study evaluated the nutrient content of different accessions of two vegetable cowpea genotypes. The mineral content of the vegetable cowpea accessions were high. Potassium content of the accessions of the climbing genotype “Akidi enu” ranged from 1.25 to 1.52% with a mean value of 1.43 ± 0.13% while in the ...

  11. Dislocation motion in tungsten: Atomistic input to discrete dislocation simulations

    Czech Academy of Sciences Publication Activity Database

    Srivastava, K.; Gröger, Roman; Weygand, D.; Gumbsch, P.

    2013-01-01

    Roč. 47, AUG (2013), s. 126-142 ISSN 0749-6419 R&D Projects: GA ČR GAP204/10/0255; GA MŠk(CZ) ED1.1.00/02.0068 Institutional support: RVO:68081723 Keywords : body -centered cubic * non-Schmid effects * anomalous slip * discrete dislocation dynamics Subject RIV: BM - Solid Matter Physics ; Magnetism; BM - Solid Matter Physics ; Magnetism (UFM-A) Impact factor: 5.971, year: 2013

  12. Unusual inferior dislocation of shoulder: reduction by two-step maneuver: a case report

    Science.gov (United States)

    Saseendar, S; Agarwal, Dinesh K; Patro, Dilip K; Menon, Jagdish

    2009-01-01

    Dislocation of the shoulder is the commonest of all large joint dislocations. Inferior dislocation constitutes 0.5% of all shoulder dislocations. It characteristically presents with overhead abduction of the arm, the humerus being parallel to the spine of scapula. We present an unusual case of recurrent luxatio erecta in which the arm transformed later into an adducted position resembling the more common anterior shoulder dislocation. Such a case has not been described before in English literature. Closed reduction by the two-step maneuver was successful with a single attempt. MRI revealed posterior labral tear and a Hill-Sachs variant lesion on the superolateral aspect of humeral head. Immobilisation in a chest-arm bandage followed by physiotherapy yielded excellent results. The case is first of its kind; the unusual mechanism, unique radiological findings and alternate method of treatment are discussed. PMID:19883514

  13. Unusual inferior dislocation of shoulder: reduction by two-step maneuver: a case report

    Directory of Open Access Journals (Sweden)

    Patro Dilip K

    2009-11-01

    Full Text Available Abstract Dislocation of the shoulder is the commonest of all large joint dislocations. Inferior dislocation constitutes 0.5% of all shoulder dislocations. It characteristically presents with overhead abduction of the arm, the humerus being parallel to the spine of scapula. We present an unusual case of recurrent luxatio erecta in which the arm transformed later into an adducted position resembling the more common anterior shoulder dislocation. Such a case has not been described before in English literature. Closed reduction by the two-step maneuver was successful with a single attempt. MRI revealed posterior labral tear and a Hill-Sachs variant lesion on the superolateral aspect of humeral head. Immobilisation in a chest-arm bandage followed by physiotherapy yielded excellent results. The case is first of its kind; the unusual mechanism, unique radiological findings and alternate method of treatment are discussed.

  14. Microstructure, quantification and control of dislocations in bast-type plant fibres

    DEFF Research Database (Denmark)

    Madsen, Bo; Lester, Catherine L.; Mortensen, Ulrich Andreas

    2016-01-01

    cellulose microfibrils, which are believed to form weak points leading to reduced mechanical properties. In the present study, microstructural observations of dislocations are made using high-magnification scanning electron microscopy. An experimental protocol using polarized optical microscopy and image...

  15. Arthroscopic treatment of acromioclavicular dislocation

    Directory of Open Access Journals (Sweden)

    Mihai T. Gavrilă

    2017-11-01

    Full Text Available A thorough understanding of biomechanical function of both acromioclavicular (AC and coracoclavicular (CC ligaments, stimulated surgeons to repair high-grade AC dislocation using arthroscopic technique. This technique necessitates a clear understanding of shoulder anatomy, especially of the structures in proximity to the clavicle and coracoid process and experiences in arthroscopic surgery. The follow case describes an arthroscopic technique used to treat AC dislocation in young man 30 years old, who suffered an injury at right shoulder. Results were similar to those obtained using open surgery and this encouraged us to continue utilization of this method. As a conclusion, arthroscopic treatment of AC separation is one of the best options as surgical treatment. Early results suggested that immediate anatomic reduction of an acute AC separation usually provides satisfactory clinical results at intermediate-term follow-up.

  16. Recurrent Dislocation of the Patella

    OpenAIRE

    Ben?tez, Gustavo

    2015-01-01

    Purpose: To evaluate results of medial patellofemoral ligament (MPFL) reconstruction associated with lateral release and advancement of vastus medialis in recurrent dislocation of the patella. Methods: We retrospectively evaluated 11 patients with a mean follow-up of 19 months. Mean age was 23, mainly women. We did MPFL reconstruction with semitendinosus or gracilis tendon depending on BMI, associated with advancement of vastus medialis and lateral release. Results: Mean Kujala score improved...

  17. Rotating effects on the scalar field in the cosmic string spacetime, in the spacetime with space-like dislocation and in the spacetime with a spiral dislocation

    Science.gov (United States)

    Vitória, R. L. L.; Bakke, K.

    2018-03-01

    In the interface between general relativity and relativistic quantum mechanics, we analyse rotating effects on the scalar field subject to a hard-wall confining potential. We consider three different scenarios of general relativity given by the cosmic string spacetime, the spacetime with space-like dislocation and the spacetime with a spiral dislocation. Then, by searching for a discrete spectrum of energy, we analyse analogues effects of the Aharonov-Bohm effect for bound states and the Sagnac effect.

  18. Plastic deformation of tubular crystals by dislocation glide.

    Science.gov (United States)

    Beller, Daniel A; Nelson, David R

    2016-09-01

    Tubular crystals, two-dimensional lattices wrapped into cylindrical topologies, arise in many contexts, including botany and biofilaments, and in physical systems such as carbon nanotubes. The geometrical principles of botanical phyllotaxis, describing the spiral packings on cylinders commonly found in nature, have found application in all these systems. Several recent studies have examined defects in tubular crystals associated with crystalline packings that must accommodate a fixed tube radius. Here we study the mechanics of tubular crystals with variable tube radius, with dislocations interposed between regions of different phyllotactic packings. Unbinding and separation of dislocation pairs with equal and opposite Burgers vectors allow the growth of one phyllotactic domain at the expense of another. In particular, glide separation of dislocations offers a low-energy mode for plastic deformations of solid tubes in response to external stresses, reconfiguring the lattice step by step. Through theory and simulation, we examine how the tube's radius and helicity affects, and is in turn altered by, the mechanics of dislocation glide. We also discuss how a sufficiently strong bending rigidity can alter or arrest the deformations of tubes with small radii.

  19. Lattice dislocation in Si nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Omar, M.S., E-mail: dr_m_s_omar@yahoo.co [Department of Physics, College of Science, University of Salahaddin, Arbil, Iraqi Kurdistan (Iraq); Taha, H.T. [Department of Physics, College of Science, University of Salahaddin, Arbil, Iraqi Kurdistan (Iraq)

    2009-12-15

    Modified formulas were used to calculate lattice thermal expansion, specific heat and Bulk modulus for Si nanowires with diameters of 115, 56, 37 and 22 nm. From these values and Gruneisen parameter taken from reference, mean lattice volumes were found to be as 20.03 A{sup 3} for the bulk and 23.63, 29.91, 34.69 and 40.46 A{sup 3} for Si nanowire diameters mentioned above, respectively. Their mean bonding length was calculated to be as 0.235 nm for the bulk and 0.248, 0.269, 0.282 and 0.297 nm for the nanowires diameter mentioned above, respectively. By dividing the nanowires diameter on the mean bonding length, number of layers per each nanowire size was found to be as 230, 104, 65 and 37 for the diameters mentioned above, respectively. Lattice dislocations in 22 nm diameter wire were found to be from 0.00324 nm for the 1st central lattice to 0.2579 nm for the last surface lattice. Such dislocation was smaller for larger wire diameters. Dislocation concentration found to change in Si nanowires according to the proportionalities of surface thickness to nanowire radius ratios.

  20. Dislocation substructure of mantle-derived olivine as revealed by selective chemical etching and transmission electron microscopy

    Science.gov (United States)

    Kirby, S.H.; Wegner, M.W.

    1978-01-01

    Cleaved and mechanically polished surfaces of olivine from peridotite xenoliths from San Carlos, Arizona, were chemically etched using the techniques of Wegner and Christie (1974). Dislocation etch pits are produced on all surface orientations and they tend to be preferentially aligned along the traces of subgrain boundaries, which are approximately parallel to (100), (010), and (001). Shallow channels were also produced on (010) surfaces and represent dislocations near the surface that are etched out along their lengths. The dislocation etch channel loops are often concentric, and emanate from (100) subgrain boundaries, which suggests that dislocation sources are in the boundaries. Data on subgrain misorientation and dislocation line orientation and arguments based on subgrain boundary energy minimization are used to characterize the dislocation structures of the subgrain boundaries. (010) subgrain boundaries are of the twist type, composed of networks of [100] and [001] screw dislocations. Both (100) and (001) subgrain boundaries are tilt walls composed of arrays of edge dislocation with Burgers vectors b=[100] and [001], respectively. The inferred slip systems are {001} ???100???, {100} ???001???, and {010} ???100??? in order of diminishing importance. Exploratory transmission electron microscopy is in accord with these identifications. The flow stresses associated with the development of the subgrain structure are estimated from the densities of free dislocations and from the subgrain dimensions. Inferred stresses range from 35 to 75 bars using the free dislocation densities and 20 to 100 bars using the subgrain sizes. ?? 1978 Springer-Verlag.

  1. Truss Climbing Robot for Space Station: Design, Analysis, and Motion Control

    Science.gov (United States)

    Chung, Wing Kwong

    The application of space robots has become more popular in performing tasks such as Intra and Extra Vehicular Activities (EVA) in Low Earth Orbit. For EVA, space robots were always designed as a chain-like manipulator with a joint configuration similar to on the earth robotic arm. Based on their joint configuration, they can be classified into two main categories. The first one is the six degrees of freedom (DOF) robotic arm including Shuttle Remote Manipulator System (SRMS), Engineering Test Satellite No. 7 (ETS-VII), the Main Arm (MA) and the Small Fine Arm (SFA) of Module Remote Manipulator System (JEMRMS). The other group is the seven-DOF space robotic arm which includes European Robotic Arm (ERA) and Space Station Remote Manipulator System (SSRMS), or Canadarm2. They not only perform manipulation tasks, but also be able to navigate on the exterior of the International Space Station (ISS). In a free floating environment, motions of a space robotic arm cause the attitude change of a space station because of their dynamic coupling effect. Hence, the stabilization of the space station attitude is important to maintain the electrical energy generated by the solar panels and the signal strength for communication. Most of research in this area focuses on the motion control of a space manipulator through the study of Generalized Jacobian Matrix. Little research has been conducted specifically on the design of locomotion mechanism of a space manipulator. This dissertation proposes a novel methodology for the locomotion on a space station which aims to lower the disturbance on a space station. Without modifying the joint configuration of conventional space manipulators, the use of a new gripping mechanism is proposed which combines the advantages of active wheels and conventional grippers. To realize the proposed gripping mechanism, this dissertation also presents the design of a novel frame climbing robot (Frambot) which is equipped with the new gripping mechanism

  2. A common perceptual parameter for stair climbing for children, young and old adults.

    Science.gov (United States)

    Cesari, P; Formenti, F; Olivato, P

    2003-02-01

    In this paper we examine whether a common perceptual parameter is available for guiding old adults, young adults and children in climbing the highest stair mountable in a bipedal fashion. Previous works have shown that the ratio between the height of the stair and the hip height was the body-scaled invariance adopted as information for selecting the highest stair by young adults [Journal of Experimental Psychology: Human Perception and Performance 10 (1984) 683-703] but not by older adults [Journal of Experimental Psychology: Human Perception and Performance 3 (1992) 691-697]. Indeed, for older adults additional bio-mechanical parameters needed to be added to the model due to their decrease in leg strength and flexibility.Up to now, no perceptual invariant has been identified yet for determining the relevant information used for guiding the stair climbing action for normal healthy people. We propose a new parameter as the angle defined by the ratio between the height of the stair and the distance taken from the feet to the top edge of the stair before the initiation of the movement. We show that this angle is the same for children, young adults and older adults despite the different kinematics of the motion, the anthropometrics and the skill ability exhibit by the participants. In summary we show that even when the climbability judgments, based on the simple ratio leg length-stair height, are influenced by differences in age, participants use a common perceptual variable when they are coordinating their stair climbing action.

  3. Rock climbing and acute emotion regulation in patients with major depressive disorder in the context of a psychological inpatient treatment: a controlled pilot trial.

    Science.gov (United States)

    Kleinstäuber, Maria; Reuter, Merle; Doll, Norbert; Fallgatter, Andreas J

    2017-01-01

    Major depressive disorder is characterized by deficits in emotion regulation. This study examined associations between rock climbing and acute emotion regulating effects in patients with major depression. In a nonrandomized, controlled study, 40 major depressive disorder inpatients were assigned to either a climbing session (n=20) or a relaxation session (n=20). Positive and negative affect, depressiveness, and coping emotions were assessed immediately before and after the session. Mixed analyses of variance and covariance revealed significant time × group interaction effects for all assessed outcomes ( p ≤0.012): positive affect and coping emotions significantly increased and negative affect and depressiveness significantly decreased after the climbing session (1.04≤ Cohen's d ≤1.30), in contrast to a relaxation session (0.16≤ Cohen's d ≤0.36). The results show that rock climbing is associated with acute emotion regulatory effects. These findings have to be replicated with a randomized design, and future research should pay attention to possible mechanisms of rock climbing in regard to emotion regulation.

  4. Luxación facetaria unilateral lumbosacra postraumática. [ Post-traumatic lumbosacral unilateral facet dislocation].

    Directory of Open Access Journals (Sweden)

    Manuel González Murillo

    2016-08-01

    Full Text Available In the literature have been reported around fifty cases of lumbosacral dislocations; treated most bilateral facet dislocations. We report the case of a female 42 year old with unilateral lumbosacral facet dislocation of one month duration after accident. Circumferential instrumented fusion L5-S1 with interbody cage and pedicle screws L5-S1 was performed.   The lumbosacral dislocation is a rare injury that occurs due to the combination of a high-energy mechanism predisposing anatomical factors. Recent publications advocate the surgical reduction and stabilization with instrumentation as standard treatment.

  5. The influence of anisotropy on the core structure of Shockley partial dislocations within FCC materials

    Science.gov (United States)

    Szajewski, B. A.; Hunter, A.; Luscher, D. J.; Beyerlein, I. J.

    2018-01-01

    two disparate dislocation length scales which describe the core structure; (i) the equilibrium stacking fault width between two Shockley partial dislocations, R eq and (ii) the maximum slip gradient, χ, of each Shockley partial dislocation. We demonstrate excellent agreement between our own analytic predictions, numerical calculations, and R eq computed directly by both ab-initio and molecular statics methods found elsewhere within the literature. The results suggest that understanding of various plastic mechanisms, e.g., cross-slip and nucleation may be augmented with the inclusion of elastic anisotropy.

  6. Imaging findings of anterior hip dislocations

    Energy Technology Data Exchange (ETDEWEB)

    Pfeifer, Kyle [Mallinckrodt Institute of Radiology, Department of Radiology, St. Louis, MO (United States); Leslie, Michael [Yale School of Medicine, Department of Orthopedics and Rehabilitation, New Haven, CT (United States); Menn, Kirsten; Haims, Andrew [Yale University School of Medicine, Department of Radiology and Biomedical Imaging, New Haven, CT (United States)

    2017-06-15

    Anterior hip dislocations are rare orthopedic emergencies resulting from high-energy trauma and have unique imaging characteristics on radiography, computed tomography (CT), and magnetic resonance imaging (MRI). Imaging findings on CT and MRI allow for the prompt recognition and classification of anterior hip dislocations, which guides patient management and reduces complications. The purpose of this article is to review imaging findings of anterior hip dislocations, specifically focusing on CT and MRI. (orig.)

  7. Imaging findings of anterior hip dislocations

    International Nuclear Information System (INIS)

    Pfeifer, Kyle; Leslie, Michael; Menn, Kirsten; Haims, Andrew

    2017-01-01

    Anterior hip dislocations are rare orthopedic emergencies resulting from high-energy trauma and have unique imaging characteristics on radiography, computed tomography (CT), and magnetic resonance imaging (MRI). Imaging findings on CT and MRI allow for the prompt recognition and classification of anterior hip dislocations, which guides patient management and reduces complications. The purpose of this article is to review imaging findings of anterior hip dislocations, specifically focusing on CT and MRI. (orig.)

  8. Climbing favours the tripod gait over alternative faster insect gaits

    Science.gov (United States)

    Ramdya, Pavan; Thandiackal, Robin; Cherney, Raphael; Asselborn, Thibault; Benton, Richard; Ijspeert, Auke Jan; Floreano, Dario

    2017-02-01

    To escape danger or catch prey, running vertebrates rely on dynamic gaits with minimal ground contact. By contrast, most insects use a tripod gait that maintains at least three legs on the ground at any given time. One prevailing hypothesis for this difference in fast locomotor strategies is that tripod locomotion allows insects to rapidly navigate three-dimensional terrain. To test this, we computationally discovered fast locomotor gaits for a model based on Drosophila melanogaster. Indeed, the tripod gait emerges to the exclusion of many other possible gaits when optimizing fast upward climbing with leg adhesion. By contrast, novel two-legged bipod gaits are fastest on flat terrain without adhesion in the model and in a hexapod robot. Intriguingly, when adhesive leg structures in real Drosophila are covered, animals exhibit atypical bipod-like leg coordination. We propose that the requirement to climb vertical terrain may drive the prevalence of the tripod gait over faster alternative gaits with minimal ground contact.

  9. Dislocations in single hemp fibres-investigations into the relationship of structural distortions and tensile properties at the cell wall level

    DEFF Research Database (Denmark)

    Thygesen, Lisbeth Garbrecht; Eder, M.; Burgert, I.

    2007-01-01

    The relationship between dislocations and mechanical properties of single hemp fibres (Cannabis sativa L. var. Felina) was studied using a microtensile testing setup in a 2-fold approach. In a first investigation the percentage of dislocations was quantified using polarized light microscopy (PLM......) prior to microtensile testing of the fibres. In a second approach PLM was used to monitor the dislocations while straining single fibres. The first part of the study comprised 53 hemp fibres with up to 20% of their cell wall consisting of dislocations. For this data set the percentage of dislocations...

  10. Lakpa Norbu 2, Why Won't Climb Everest

    OpenAIRE

    Loomis, Molly

    2012-01-01

    .wav and .mp3 versions of audio file Lakpa Norbu Sherpa explains why as the only son in his family, they won’t allow him to climb Mount Everest. These recordings were made on a trek in the spring of 2011 up to Mount Everest Base Camp. The recordings span a wide variety of topics from making and drinking chang to the work of Mount Everest's 'ice fall doctors'.

  11. Climbing out of the nuclear valley

    CERN Document Server

    Boutin, C

    2002-01-01

    With nuclear physics largely confined to a narrow band of stable isotopes, a new US machine aims to provide a wider nuclear perspective. An innovative, exotic-beam facility now under consideration, the Rare Isotope Accelerator (RIA), could extend the horizons of nuclear physics greatly. RIA brings together a range of technologies to produce intense and high-quality beams of short-lived radionuclides of all of the chemical elements, from the lightest to the heaviest. The short-lived, rare isotopes are produced by a continuous-wave, superconducting 1.4 GV driver linac that will deliver 400 kW beams of any mass from 900 MeV protons to 400 MeV per nucleon uranium. The main production mechanisms are spallation and fission of heavy targets by light ions and in-flight fragmentation or fission of heavy-ion beams.

  12. [Traumatic lumbosacral dislocation - an underrated injury].

    Science.gov (United States)

    Schroeter, S; Weise, K; Badke, A

    2009-01-01

    Traumatic lumbosacral dislocations are rare. We report two cases with initially missed posttraumatic lumbosacral dislocations. The reported cases and the review of the literature show that, especially, accident victims with multiple fractures of the lumbar transverses processes may require a CT scan to confirm fractures or dislocations of L5/S1. Follow-up examinations due to persisting pain after physiotherapy should include lateral X-rays of the lumbar spine of the patient standing. According to the literature and our experience, the treatment of traumatic lumbosacral dislocation usually consists of open reduction and postero-lateral or dorso-ventral fusion of the unstable segments.

  13. Structure of the Dislocation in Sapphire

    DEFF Research Database (Denmark)

    Bilde-Sørensen, Jørgen; Thölen, A. R.; Gooch, D. J.

    1976-01-01

    Experimental evidence of the existence of 01 0 dislocations in the {2 0} prism planes in sapphire has been obtained by transmission electron microscopy. By the weak-beam technique it has been shown that the 01 0 dislocations may dissociate into three partials. The partials all have a Burgers vector...... of ⅓ 01 0 and are separated by two identical faults. The distance between two partials is in the range 75-135 Å, corresponding to a fault energy of 320±60 mJ/m2. Perfect 01 0 dislocations have also been observed. These dislocations exhibited either one or two peaks when imaged in the (03 0) reflection...

  14. Hip Dislocation or Subluxation After Hip Arthroscopy: A Systematic Review.

    Science.gov (United States)

    Duplantier, Neil L; McCulloch, Patrick C; Nho, Shane J; Mather, Richard C; Lewis, Brian D; Harris, Joshua D

    2016-07-01

    To determine patient- and surgery-specific characteristics of patients sustaining postarthroscopic hip dislocation or subluxation. A systematic review of multiple medical databases was registered with PROSPERO and performed using Preferred Reporting Items for Systemic Reviews and Meta-Analysis guidelines. Level I to IV clinical outcome studies reporting the presence of hip dislocation or subluxation after hip arthroscopy were eligible. Length of follow-up was not an exclusion criterion. All patient- and surgery-specific variables were extracted from each, specifically evaluating osseous morphology and resection details; labral, iliopsoas, ligamentum teres, and capsular management; generalized ligamentous laxity; instability direction and mechanism; management; and outcome. Study authors were individually contacted to assess most recent outcome. Ten articles with 11 patients were analyzed (mean patient age: 36.6 ± 12.3 years). There were 9 hip dislocations and 2 subluxations. Mean time between surgery and dislocation was 3.2 ± 4.0 months (range: recovery room to 14 months). Anterior was the most frequent dislocation direction (8 cases). Acetabular undercoverage (preoperative dysplasia or iatrogenic rim over-resection) was observed in 5 cases. Labral debridement was performed in 5 cases, iliopsoas tenotomy in 3 cases, and ligamentum teres debridement in 1 case. A "T" capsulotomy was created in 1 case (isolated interportal in other 10 cases). Capsular closure was performed in 2 cases (both interportal). Generalized ligamentous laxity was diagnosed in 1 case. A combination of external rotation and extension was observed in 5 of the 6 cases reporting the mechanism of anterior dislocation. Four cases were successfully treated with closed reduction; 4 required total hip arthroplasty; and 3 required revision capsulorrhaphy. Postarthroscopic hip instability was observed in patients with acetabular undercoverage (including iatrogenic resection), labral debridement

  15. On the static structural design of climbing robots: part 1.

    Science.gov (United States)

    Ahmed, Ausama Hadi; Menon, Carlo

    This manuscript is the first of two parts of a work investigating optimal configurations of legged climbing robots while loitering on vertical surfaces. In this part 1, a mathematical model of a climbing robot based on the finite element method (FEM), specifically the stiffness method, is generated. A number of parameters, namely the height of the robot, the length of its body and the position of its legs, are investigated to assess their effect on the adhesion requirements needed for the robot to stay attached to a wall. Predictions of the developed mathematical model are validated using FEM commercial software. The body and the legs are assumed to be perpendicular to each other in this part 1. The effect of their inclination is investigated in the subsequent part 2 of our work. In part 2, the model is also used to predict postures that ants have while standing on vertical surfaces. The model is validated by comparing the predicted results to images of loitering ants. The parameters investigated provide guidelines to design legged climbing robots.

  16. Dislocation dissociation and stacking-fault energy calculation in strontium titanate

    International Nuclear Information System (INIS)

    Castillo-Rodriguez, M.; Sigle, W.

    2010-01-01

    The dislocation microstructure of strontium titanate plastically deformed below room temperature shows dipolar configurations of a screw dislocations. The dipole height is so small that dipole annihilation is expected. Here we show why this is inhibited. By high-resolution transmission electron microscopy observations we find that in such dipoles each dislocation is dissociated into two collinear a/2 partials on a {1 1 0} plane. Elasticity theory calculations provide a stacking-fault energy value of 340 ± 90 mJ m -2 . Finally, we discuss the effects of this dissociation process on the mechanical behaviour.

  17. Cyclic softening in annealed Zircaloy-2: Role of edge dislocation dipoles and vacancies

    Science.gov (United States)

    Sudhakar Rao, G.; Singh, S. R.; Krsjak, Vladimir; Singh, Vakil

    2018-04-01

    The mechanism of cyclic softening in annealed Zircaloy-2 at low strain amplitudes under strain controlled fatigue at room temperature is rationalized. The unusual softening due to continuous decrease in the phenomenological friction stress is found to be associated with decrease in the resistance against movement of dislocations because of the formation and easy glide of pure edge dislocation dipoles and consequent decrease in friction stress from reduction in the shear modulus. Positron annihilation spectroscopy data strongly support the increase in edge dislocation density containing jogs, from increased positron trapping and increase in annihilation lifetime.

  18. Traumatic atlantooccipital dislocation with survival: case report and review of the literature.

    Science.gov (United States)

    Guigui, P; Milaire, M; Morvan, G; Lassale, B; Deburge, A

    1995-01-01

    We present the case of a patient with traumatic atlantooccipital dislocation. The initial neurological examination showed no abnormalities. Dislocation was the result of rapid deceleration in a motor vehicle accident. The mechanism of injury was hyperextension/rotation, probably combined with a distraction force. Only a few cases of atlantooccipital dislocation without neurological involvement have been reported. Every report pointed out difficulties of initial diagnosis. Special attention should be directed toward the atlanto-odontoid-basion relationships as seen on lateral radiographs. Prompt recognition and surgical stabilization are essential to avoid further neurological injury.

  19. Metal working and dislocation structures

    DEFF Research Database (Denmark)

    Hansen, Niels

    2007-01-01

    Microstructural observations are presented for different metals deformed from low to high strain by both traditional and new metal working processes. It is shown that deformation induced dislocation structures can be interpreted and analyzed within a common framework of grain subdivision on a finer...... and finer scale down to the nanometer dimension, which can be reached at ultrahigh strains. It is demonstrated that classical materials science and engineering principles apply from the largest to the smallest structural scale but also that new and unexpected structures and properties characterize metals...

  20. Dislocation

    Science.gov (United States)

    ... There is no substitute for close supervision, no matter how safe the environment or situation appears to ... ADAM Health Solutions. About MedlinePlus Site Map FAQs Customer Support Get email updates Subscribe to RSS Follow ...

  1. PREFACE: DISLOCATIONS 2008 An International Conference on the Fundamentals of Plastic Deformation

    Science.gov (United States)

    Cai, Wei; Edagawa, Keiichi; Ngan, Alfonso H. W.

    2009-07-01

    Crystal dislocations are fundamental carriers of plastic deformation in crystalline materials and a good understanding of their behavior forms the scientific basis for improving our ability to manufacture new materials of high mechanical strength. After their initial proposal in 1934, crystal dislocations have become the focus of intense research following their first direct observation in a transmission electron microscope in the 1950's. The last decade has witnessed a new burst of interest and activity in the field, driven in part by the desire to understand the fundamental mechanisms of plasticity in materials at smaller scales, and enabled by significant breakthroughs in both experimental and computational tools. To facilitate information exchange and academic discussions, the ''Dislocations 200X'' international conference series was established in 2000 and has since become the major world forum on crystal dislocations taking place every four years on average. The relatively long period between the conferences leaves sufficient time for new ideas to develop and become worthy of a wide discussion. An important goal of the ''Dislocations 200X'' series is to encourage young researchers to engage in direct communications with the scientists of older generations. The scope of the ''Dislocations 200X'' conference includes fundamental research on dislocations in all types of materials and their role in plasticity. The ''Dislocations 2008'', the third in the series, was held in Hong Kong, 13-17 October 2008. The choice of this conference site reflects the desire to strengthen the connection between scientists on the continents of North America, Europe and Asia. Over 60 talks and 60 posters were presented at the Dislocations 2008 conference. Some presentations have led to papers that are published in this volume after review. Editors: Wei Cai (Stanford University, USA) Keiichi Edagawa (Tokyo University, Japan) Alfonso H W Ngan (Hong Kong University, China)

  2. Use of a hypobaric chamber for pre-acclimatization before climbing Mount Everest.

    Science.gov (United States)

    Richalet, J P; Bittel, J; Herry, J P; Savourey, G; Le Trong, J L; Auvert, J F; Janin, C

    1992-10-01

    Climbing Mount Everest needs an acclimatization period of 3 to 4 weeks between 3000 and 6000 m. In order to reduce this period of time spent in dangerous conditions, an experience of pre-acclimatization was performed with 5 elite alpinists (4 male, 1 female), aged 30 +/- 4 yrs (mean +/- SD), before their attempt to climb Mount Everest. Subjects first remained one week on Mont-Blanc (between 4350 and 4807 m), then spent a total of 38 hours in a hypobaric chamber (in 4 consecutive days) from 5000 to 8500 m standard altitude. Then, they flew to Kathmandu and reached 7800 m five days only after leaving the base camp. The pre-acclimatization period showed a 12% increase in hemoglobin concentration, and no change in ventilatory response to hypoxia. Arterial oxygen saturation at submaximal exercise in hypoxia (FIO2 = 0.115) increased from 75 +/- 4 to 82 +/- 3%, probably because of an efficient ventilatory acclimatization. On Mount Everest, the speed of ascent was very high (5600 m of altitude gain in 6 days), knowing that in conventional expeditions, 12 to 32 days are generally necessary to reach, safe, the same altitude. In conclusion, pre-acclimatization seems to have triggered efficient mechanisms which allowed climbers to save 1 to 3 weeks of time in mountain conditions.

  3. Video Analysis of Primary Shoulder Dislocations in Rugby Tackles

    Science.gov (United States)

    Maki, Nobukazu; Kawasaki, Takayuki; Mochizuki, Tomoyuki; Ota, Chihiro; Yoneda, Takeshi; Urayama, Shingo; Kaneko, Kazuo

    2017-01-01

    Background: Characteristics of rugby tackles that lead to primary anterior shoulder dislocation remain unclear. Purpose: To clarify the characteristics of tackling that lead to shoulder dislocation and to assess the correlation between the mechanism of injury and morphological damage of the glenoid. Study Design: Case series; Level of evidence, 4. Methods: Eleven elite rugby players who sustained primary anterior shoulder dislocation due to one-on-one tackling between 2001 and 2014 were included. Using an assessment system, the tackler’s movement, posture, and shoulder and head position were evaluated in each phase of tackling. Based on 3-dimensional computed tomography, the glenoid of the affected shoulder was classified into 3 types: intact, erosion, and bone defect. Orientation of the glenoid defect and presence of Hill-Sachs lesion were also evaluated. Results: Eleven tackles that led to primary shoulder dislocation were divided into hand, arm, and shoulder tackle types based on the site at which the tackler contacted the ball carrier initially. In hand and arm tackles, the tackler’s shoulder joint was forcibly moved to horizontal abduction by the impact of his upper limb, which appeared to result from an inappropriate approach to the ball carrier. In shoulder tackles, the tackler’s head was lowered and was in front of the ball carrier at impact. There was no significant correlation between tackle types and the characteristics of bony lesions of the shoulder. Conclusion: Although the precise mechanism of primary anterior shoulder dislocation could not be estimated from this single-view analysis, failure of individual tackling leading to injury is not uniform and can be caused by 2 main factors: failure of approach followed by an extended arm position or inappropriate posture of the tackler at impact, such as a lowered head in front of the opponent. These findings indicate that injury mechanisms should be assessed for each type of tackle, as it is unknown

  4. Evaluation of injury and fatality risk in rock and ice climbing.

    Science.gov (United States)

    Schöffl, Volker; Morrison, Audry; Schwarz, Ulrich; Schöffl, Isabelle; Küpper, Thomas

    2010-08-01

    Rock and ice climbing are widely considered to be 'high-risk' sporting activities that are associated with a high incidence of severe injury and even death, compared with more mainstream sports. However, objective scientific data to support this perception are questionable. Accordingly, >400 sport-specific injury studies were analysed and compared by quantifying the injury incidence and objectively grading the injury severity (using the National Advisory Committee for Aeronautics score) per 1000 hours of sporting participation. Fatalities were also analysed. The analysis revealed that fatalities occurred in all sports, but it was not always clear whether the sport itself or pre-existing health conditions contributed or caused the deaths. Bouldering (ropeless climbing to low heights), sport climbing (mostly bolt protected lead climbing with little objective danger) and indoor climbing (climbing indoors on artificial rock structures), showed a small injury rate, minor injury severity and few fatalities. As more objective/external dangers exist for alpine and ice climbing, the injury rate, injury severity and fatality were all higher. Overall, climbing sports had a lower injury incidence and severity score than many popular sports, including basketball, sailing or soccer; indoor climbing ranked the lowest in terms of injuries of all sports assessed. Nevertheless, a fatality risk remains, especially in alpine and ice climbing. In the absence of a standard definition for a 'high-risk' sport, categorizing climbing as a high-risk sport was found to be either subjective or dependent on the definition used. In conclusion, this analysis showed that retrospective data on sport-specific injuries and fatalities are not reported in a standardized manner. To improve preventative injury measures for climbing sports, it is recommended that a standardized, robust and comprehensive sport-specific scoring model should be developed to report and fully evaluate the injury risk, severity

  5. Hybrid dislocated control and general hybrid projective dislocated synchronization for the modified Lue chaotic system

    Energy Technology Data Exchange (ETDEWEB)

    Xu Yuhua [College of Information Science and Technology, Donghua University, Shanghai 201620 (China) and Department of Maths, Yunyang Teacher' s College, Hubei 442000 (China)], E-mail: yuhuaxu2004@163.com; Zhou Wuneng [College of Information Science and Technology, Donghua University, Shanghai 201620 (China)], E-mail: wnzhou@163.com; Fang Jianan [College of Information Science and Technology, Donghua University, Shanghai 201620 (China)

    2009-11-15

    This paper introduces a modified Lue chaotic system, and some basic dynamical properties are studied. Based on these properties, we present hybrid dislocated control method for stabilizing chaos to unstable equilibrium and limit cycle. In addition, based on the Lyapunov stability theorem, general hybrid projective dislocated synchronization (GHPDS) is proposed, which includes complete dislocated synchronization, dislocated anti-synchronization and projective dislocated synchronization as its special item. The drive and response systems discussed in this paper can be strictly different dynamical systems (including different dimensional systems). As examples, the modified Lue chaotic system, Chen chaotic system and hyperchaotic Chen system are discussed. Numerical simulations are given to show the effectiveness of these methods.

  6. Grasping Claws of Bionic Climbing Robot for Rough Wall Surface: Modeling and Analysis

    Directory of Open Access Journals (Sweden)

    Quansheng Jiang

    2017-12-01

    Full Text Available Aiming at the inspection of rough stone and concrete wall surfaces, a grasping module of cross-arranged claw is designed. It can attach onto rough wall surfaces by hooking or grasping walls. First, based on the interaction mechanism of hooks and rough wall surfaces, the hook structures in claw tips are developed. Then, the size of the hook tip is calculated and the failure mode is analyzed. The effectiveness and reliability of the mechanism are verified through simulation and finite element analysis. Afterwards, the prototype of the grasping module of claw is established to carry out grasping experiment on vibrating walls. Finally, the experimental results demonstrate that the proposed cross-arranged claw is able to stably grasp static wall surfaces and perform well in grasping vibrating walls, with certain anti-rollover capability. This research lays a foundation for future researches on wall climbing robots with vibrating rough wall surfaces.

  7. Transverse divergent dislocation of elbow in a child: a case report and review of current literature.

    Science.gov (United States)

    George, Harvey L; Unnikrishnan, Puthanveetil Nithin; Bass, Alfie; Waseem, Mohammed; Brownson, Peter

    2011-05-01

    We present a case report on transverse divergent dislocation of the elbow, highlighting the spatial relation among the proximal radius, ulna, and distal humerus in this rare pediatric elbow injury and reasons leading to misinterpretation of radiographs. Elbow dislocation is a rare injury in children. It comprises only 6% of pediatric elbow injuries. Most pure dislocations are posterior, but they can occur in any direction. Divergent dislocation of the elbow is a subgroup of posterior dislocation, which is extremely rare. It is important that the pediatric emergency physician is aware, able to identify, and manage this injury. It is defined as a specific elbow dislocation in which the distal humerus is forced between the proximal radius and ulna, resulting in the divergence of the proximal forearm bones. Joint laxity is said to be a predisposing cause in pediatric age group. Atraumatic divergent dislocation of the elbow has been reported in the adults with rheumatoid arthritis. Imaging is challenging because there is no defined specific radiological views, therefore making the diagnosis difficult. This often leads to misdiagnosis or inappropriate treatment. A thorough understanding of mechanism of injury and basis for atypical radiological findings will help in identifying the injury early, and the simple Thompson technique to relocate the elbow will give an excellent functional outcome.

  8. Dislocation and Structural Studies at Metal-Metallic Glass Interface at Low Temperature

    Science.gov (United States)

    Gupta, Pradeep; Yedla, Natraj

    2017-12-01

    In this paper, molecular dynamics (MD) simulation deformation studies on the Al (metal)-Cu50Zr50 (metallic glass) model interface is carried out based on cohesive zone model. The interface is subjected to mode-I loading at a strain rate of 109 s-1 and temperature of 100 K. The dislocations reactions and evolution of dislocation densities during the deformation have been investigated. Atomic interactions between Al, Cu and Zr atoms are modeled using EAM (embedded atom method) potential, and a timestep of 0.002 ps is used for performing the MD simulations. A circular crack and rectangular notch are introduced at the interface to investigate the effect on the deformation behavior and fracture. Further, scale size effect is also investigated. The structural changes and evolution of dislocation density are also examined. It is found that the dominant deformation mechanism is by Shockley partial dislocation nucleation. Amorphization is observed in the Al regions close to the interface and occurs at a lower strain in the presence of a crack. The total dislocation density is found to be maximum after the first yield in both the perfect and defect interface models and is highest in the case of perfect interface with a density of 6.31 × 1017 m-2. In the perfect and circular crack defect interface models, it is observed that the fraction of Shockley partial dislocation density decreases, whereas that of strain rod dislocations increases with increase in strain.

  9. Accumulation of dislocation loops in the α phase of Zr Excel alloy under heavy ion irradiation

    Science.gov (United States)

    Yu, Hongbing; Yao, Zhongwen; Idrees, Yasir; Zhang, He K.; Kirk, Mark A.; Daymond, Mark R.

    2017-08-01

    In-situ heavy ion irradiations were performed on the high Sn content Zr alloy 'Excel', measuring type dislocation loop accumulation up to irradiation damage doses of 10 dpa at a range of temperatures. The high content of Sn, which diffuses slowly, and the thin foil geometry of the sample provide a unique opportunity to study an extreme case where displacement cascades dominate the loop formation and evolution. The dynamic observation of dislocation loop evolution under irradiation at 200 °C reveals that type dislocation loops can form at very low dose (0.0025 dpa). The size of the dislocation loops increases slightly with irradiation damage dose. The mechanism controlling loop growth in this study is different from that in neutron irradiation; in this study, larger dislocation loops can condense directly from the interaction of displacement cascades and the high concentration of point defects in the matrix. The size of the dislocation loop is dependent on the point defect concentration in the matrix. A negative correlation between the irradiation temperature and the dislocation loop size was observed. A comparison between cascade dominated loop evolution (this study), diffusion dominated loop evolution (electron irradiation) and neutron irradiation suggests that heavy ion irradiation alone may not be enough to accurately reproduce neutron irradiation induced loop structures. An alternative method is proposed in this paper. The effects of Sn on the displacement cascades, defect yield, and the diffusion behavior of point defects are established.

  10. Anterior bilateral temporomandibular joint dislocation: an ...

    African Journals Online (AJOL)

    Anterior dislocation of the temporomandibular joint (TMJ) though an infrequent presentation at the emergency department; often demands an immediate reduction to relieve discomfort and prevent adverse long-term sequelae. A simple and effective technique to reduce the dislocation is successfully demonstrated by putting ...

  11. On establishing coreference in Left Dislocation constructions ...

    African Journals Online (AJOL)

    The phenomenon of left dislocation (LD) has received relatively little attention in the generative literature. In Government & Binding theory and early versions of Minimalist Syntax, the left-dislocated expression is conventionally taken to be base-generated in its sentence-initial surface position and the resumptive pronoun in ...

  12. Slip systems, lattice rotations and dislocation boundaries

    DEFF Research Database (Denmark)

    Winther, Grethe

    2008-01-01

    of dislocation structure formed, in particular the crystallographic alignment of dislocation boundaries, and the slip pattern are demonstrated. These relations are applied to polycrystals deformed in tension and rolling, producing good agreement with experiment for rolling but less good agreement for tension...

  13. Interactions between Dislocations and Grain Boundaries

    NARCIS (Netherlands)

    Soer, Wouter Anthon

    2006-01-01

    Dislocations (line defects) and grain boundaries (planar defects) are two types of lattice defects that are crucial to the deformation behavior of metals. Permanent deformation of a crystalline material is microscopically associated with the nucleation and propagation of dislocations, and extensive

  14. Traumatic atlantooccipital dislocation: two cases with survival.

    Science.gov (United States)

    Bools, J C; Rose, B S

    1986-01-01

    These two cases with long-term survival after anterior and posterior AO dislocation point out the importance of making the diagnosis. Our simple technique of rapid CT confirmation of AO dislocation is a practical adjuvant procedure, particularly in patients with suspected intracranial injury.

  15. Palmar dislocation of scaphoid and lunate

    Directory of Open Access Journals (Sweden)

    Khalid Koulali Idrissi

    2011-11-01

    Full Text Available A palmar dislocation of scaphoid and lunate is uncommon. We have found only 19 reported cases in the literature. We reported a simultaneous, divergent dislocation. The closed reduction followed by percutaneous pinning has given a good result without avascular necrosis of any carpal bone.

  16. Empirical potential and elasticity theory modelling of interstitial dislocation loops in UO2 for cluster dynamics application

    International Nuclear Information System (INIS)

    Le-Prioux, Arno

    2017-01-01

    During irradiation in reactor, the microstructure of UO 2 changes and deteriorates, causing modifications of its physical and mechanical properties. The kinetic models used to describe these changes such as cluster dynamics (CRESCENDO calculation code) consider the main microstructural elements that are cavities and interstitial dislocation loops, and provide a rather rough description of the loop thermodynamics. In order to tackle this issue, this work has led to the development of a thermodynamic model of interstitial dislocation loops based on empirical potential calculations. The model considers two types of interstitial dislocation loops on two different size domains: Type 1: Dislocation loops similar to Frank partials in F.C.C. materials which are stable in the smaller size domain. Type 2: Perfect dislocation loops of Burgers vector (a/2)(110) stable in the larger size domain. The analytical formula used to compute the interstitial dislocation loop formation energies is the one for circular loops which has been modified in order to take into account the effects of the dislocation core, which are significant at smaller sizes. The parameters have been determined by empirical potential calculations of the formation energies of prismatic pure edge dislocation loops. The effect of the habit plane reorientation on the formation energies of perfect dislocation loops has been taken into account by a simple interpolation method. All the different types of loops seen during TEM observations are thus accounted for by the model. (author) [fr

  17. Re-dislocation after revision total hip arthroplasty for recurrent dislocation: a multicentre study.

    Science.gov (United States)

    Yoshimoto, Kensei; Nakashima, Yasuharu; Aota, Shigeo; Kaneuji, Ayumi; Fukui, Kiyokazu; Hirakawa, Kazuo; Nakura, Nariaki; Kinoshita, Koichi; Naito, Masatoshi; Iwamoto, Yukihide

    2017-02-01

    Although most case of dislocations after total hip arthroplasty (THA) can be managed with conservative treatment, recurrent dislocation may require surgical intervention. This multicentre study was conducted to evaluate the re-dislocation rate after revision THA for recurrent dislocation, and to determine the risk factors for re-dislocation. We retrospectively reviewed the 88 hips in 88 patients who underwent revision THA for recurrent dislocation at five institutions between 1995 and 2014. The mean patient age at surgery was 68.5 years and the mean follow-up period was 53.1 months. Multivariate logistic regression was performed to identify risk factors for re-dislocation. Sixteen hips in 16 patients (18.2 %) re-dislocated at a mean of 25.5 months (range, 1-83 months) after revision THA. Multivariate analysis identified osteonecrosis of the femoral head (odds ratio [OR] = 5.62 vs. osteoarthritis) and a femoral head size hips required additional revision THA for re-dislocation. The re-dislocation rate after revision THA for recurrent dislocation remains high, suggesting the need for prevention measures. We recommend the use of a femoral head size ≥ 32 mm.

  18. Dislocation evolution during plastic deformation: Equations vs. discrete dislocation dynamics study

    Science.gov (United States)

    Davoudi, Kamyar M.; Vlassak, Joost J.

    2018-02-01

    Equations for dislocation evolution bridge the gap between dislocation properties and continuum descriptions of plastic behavior of crystalline materials. Computer simulations can help us verify these evolution equations and find their fitting parameters. In this paper, we employ discrete dislocation dynamics to establish a continuum-based model for the evolution of the dislocation structure in polycrystalline thin films. Expressions are developed for the density of activated dislocation sources, as well as dislocation nucleation and annihilation rates. We demonstrate how size effect naturally enters the evolution equation. Good agreement between the simulation and the model results is obtained. The current approach is based on a two-dimensional discrete dislocation dynamics model but can be extended to three-dimensional models.

  19. Rules for Forest Interactions between Dislocations

    International Nuclear Information System (INIS)

    Wickham, L. K.; Schwarz, K. W.; Stoelken, J. S.

    1999-01-01

    The dynamical interactions of dislocations existing on intersecting glide planes have been investigated using numerical simulations based on isotropic linear elastic theory. It is found that such dislocations either repel, attract and form growing junctions, or attract and form bound crossed states. Which of these occurs can be predicted from a surprisingly simple analysis of the initial configurations. The outcome is determined primarily by the angles which the dislocations initially make with the glide-plane intersection edge, and is largely independent of the initial distance between the dislocations, their initial curvature, or ambient applied stresses. The results provide a rule for dealing with forest interactions within the context of large multiple-dislocation computations. (c) 1999 The American Physical Society

  20. Dissociated dislocations in Ni: a computational study

    International Nuclear Information System (INIS)

    Szelestey, P.; Patriarca, M.; Kaski, K.

    2005-01-01

    A systematic computational study of the behavior of a (1/2) dissociated screw dislocation in fcc nickel is presented, in which atomic interactions are described through an embedded-atom potential. A suitable external stress is applied on the system, both for modifying the equilibrium separation distance d and moving the dislocation complex. The structure of the dislocation and its corresponding changes during the motion are studied in the framework of the two-dimensional Peierls model, for different values of the ratio d/a', where a' is the period of the Peierls potential. The distance between the edge and screw components of the partials, as well as their widths, undergo a modulation with period a', as the dislocation moves, and the amplitudes of such oscillations are shown to depend on d/a'. The stress profile acting on the dislocation complex is analyzed and the effective Peierls stress is estimated for different values of d/a'

  1. Influence of mobile dislocations on phase separation in binary alloys

    International Nuclear Information System (INIS)

    Haataja, Mikko; Leonard, Francois

    2004-01-01

    We introduce a continuum model to describe the phase separation of a binary alloy in the presence of mobile dislocations. The kinetics of the local composition and dislocation density are coupled through their elastic fields. We show both analytically and numerically that mobile dislocations modify the standard spinodal decomposition process, and lead to several regimes of growth. Depending on the dislocation mobility and observation time, the phase separation may be accelerated, decelerated, or unaffected by mobile dislocations. For any finite dislocation mobility, we show that the domain growth rate asymptotically becomes independent of the dislocation mobility, and is faster than the dislocation-free growth rate

  2. The effectiveness of chocolate milk as a post-climbing recovery aid.

    Science.gov (United States)

    Potter, J; Fuller, B

    2015-12-01

    Recovery is essential to effective performance in climbing competitions which often involve repeated bouts, and sport climbing where climbers may work a route over a number of days prior to a complete ascent. This study employed a cross-over design to compare water with chocolate milk as recovery aids following an exhaustive bout of high intensity endurance climbing. Ten male climbers (age: 22±1 years; height: 178.5±7.9 cm; mass: 74.7±11.3 kg) climbed a Tredwall (Brewer Ledge M6) until volitional exhaustion. The participants consumed either water or chocolate milk 20 minutes after the climb and then again with their evening meal. The exercise protocol was repeated 24 hours after the original climb. The second condition was completed 7 days later. Workload indicators of heart rate, rate of perceived exertion (RPE), blood lactate and muscle soreness scores were recorded alongside climbing performance measures of duration and distance of the climb. A improved performance was found after the consumption of chocolate milk, with both a greater distance climbed (F(1,9)=11.704, P=0.008) and duration (F(1,9) =10.922, P=0.009), there were no differences in end of climb heart rate or RPE. Muscle soreness scores were lower three days after exercise following chocolate milk (t(8)=3.773, P=0.005). Chocolate milk as a recovery drink resulted in further sustained climbing, a decrease in muscle soreness, compared to water. It may be pertinent for climbers to consider its use as a recovery aid during repeated climbing bouts. Chocolate milk is a relatively unexplored recovery aid and warrants further attention.

  3. Amount of balance necessary for the independence of transfer and stair-climbing in stroke inpatients.

    Science.gov (United States)

    Fujita, Takaaki; Sato, Atsushi; Ohashi, Yuji; Nishiyama, Kazutaka; Ohashi, Takuro; Yamane, Kazuhiro; Yamamoto, Yuichi; Tsuchiya, Kenji; Otsuki, Koji; Tozato, Fusae

    2018-05-01

    The purpose of this study was to clarify the amount of balance necessary for the independence of transfer and stair-climbing in stroke patients. This study included 111 stroke inpatients. Simple and multiple regression analyses were conducted to establish the association between the FIM ® instrument scores for transfer or stair-climbing and Berg Balance Scale. Furthermore, receiver operating characteristic curves were used to elucidate the amount of balance necessary for the independence of transfer and stair-climbing. Simple and multiple regression analyses showed that the FIM ® instrument scores for transfer and stair-climbing were strongly associated with Berg Balance Scale. On comparison of the independent and supervision-dependent groups, Berg Balance Scale cut-off values for transfer and stair-climbing were 41/40 and 54/53 points, respectively. On comparison of the independent-supervision and dependent groups, the cut-off values for transfer and stair-climbing were 30/29 and 41/40 points, respectively. The calculated cut-off values indicated the amount of balance necessary for the independence of transfer and stair-climbing, with and without supervision, in stroke patients. Berg Balance Scale has a good discriminatory ability and cut-off values are clinically useful to determine the appropriate independence levels of transfer and stair-climbing in hospital wards. Implications for rehabilitation The Berg Balance Scale's (BBS) strong association with transfer and stair-climbing independence and performance indicates that establishing cut-off values is vitally important for the established use of the BBS clinically. The cut-off values calculated herein accurately demonstrate the level of balance necessary for transfer and stair-climbing independence, with and without supervision, in stroke patients. These criteria should be employed clinically for determining the level of independence for transfer and stair-climbing as well as for setting balance training

  4. Recurrent Dislocation of the Patella

    Science.gov (United States)

    Benítez, Gustavo

    2015-01-01

    Purpose: To evaluate results of medial patellofemoral ligament (MPFL) reconstruction associated with lateral release and advancement of vastus medialis in recurrent dislocation of the patella. Methods: We retrospectively evaluated 11 patients with a mean follow-up of 19 months. Mean age was 23, mainly women. We did MPFL reconstruction with semitendinosus or gracilis tendon depending on BMI, associated with advancement of vastus medialis and lateral release. Results: Mean Kujala score improved from 46,54 pts. preoperative to 88,36 postoperative. Our main complication was 1 patient with rigid knee, who required movilization under anesthesia and arthroscopic arthrolisis to improve her outcome. Conclusion: The combination of this techniques are a good alternative to treat patients with recurrent patella disclocation, with good short and mid-term results. Biomechanic intra and postop complications of MPFL reconstruction are related to patellar fixation, anatomic positioning of femoral tunnel and knee position of the graft fixation.

  5. Distributed mechatronics controller for modular wall climbing robot

    CSIR Research Space (South Africa)

    Tlale, NS

    2006-07-01

    Full Text Available the fourth motor and the suction cup up and down during locomotion. The fourth motor and the suction cup are attached on the same housing. Purpose of this fourth motor is also to move the suction cup up and down during the locomotion of the robot.... The third and the fourth motors act together to achieve a smooth contact surface between the suction cup and the surface that is being moved upon. In order to assemble wall-climbing robot that consists of any number of biped modules, each biped module...

  6. Stress-induced formation mechanism of stacking fault tetrahedra in nano-cutting of single crystal copper

    International Nuclear Information System (INIS)

    Wang, Quanlong; Bai, Qingshun; Chen, Jiaxuan; Guo, Yongbo; Xie, Wenkun

    2015-01-01

    Graphical abstract: In this paper, molecular dynamics simulation is performed to study the distribution of dislocation defects and local atomic crystal structure of single crystal copper. The stress distribution is investigated which is calculated by virial stress and analyzed by static pressure. The results are shown in (a)–(d). It is indicated that the compressive stress mainly spreads over the shear-slip zone, and the tensile stress is consisted in flank friction zone, shown in (a). The high tensile stress in subsurface is the source of stress, shown in (b). By the driven action of the stress source, the initial stair-rod dislocation nucleates. Then the dislocation climbs along four {1 1 1} planes under the stress driven action, shown in (d). Finally, the SFT is formed by the interaction of the compressive stress and the tensile stress which come from the shear-slip zone and friction zone, respectively. Besides, stair-rod dislocation, stacking faults and dislocation loop are also nucleated in the subsurface, shown in (c). Dislocation distribution, local atomic crystal structure state and stress-induced formation process of SFT by atomic. - Highlights: • A novel defect structure “stress-induced stacking fault tetrahedra” is revealed. • Atomic structural evolution and stress state distribution of the SFT are studied. • The stress-induced formation mechanism of the SFT is proposed. - Abstract: Stacking fault tetrahedra commonly existed in subsurface of deformed face center cubic metals, has great influence on machining precision and surface roughness in nano-cutting. Here we report, a stacking fault tetrahedra is formed in subsurface of workpiece during nano-cutting. The variation of cutting force and subsurface defects distribution are studied by using molecular dynamics simulation. The stress distribution is investigated which is calculated by virial stress and analyzed by static compression. The result shows that the cutting force has a rapidly

  7. Single-step collision-free trajectory planning of biped climbing robots in spatial trusses.

    Science.gov (United States)

    Zhu, Haifei; Guan, Yisheng; Chen, Shengjun; Su, Manjia; Zhang, Hong

    For a biped climbing robot with dual grippers to climb poles, trusses or trees, feasible collision-free climbing motion is inevitable and essential. In this paper, we utilize the sampling-based algorithm, Bi-RRT, to plan single-step collision-free motion for biped climbing robots in spatial trusses. To deal with the orientation limit of a 5-DoF biped climbing robot, a new state representation along with corresponding operations including sampling, metric calculation and interpolation is presented. A simple but effective model of a biped climbing robot in trusses is proposed, through which the motion planning of one climbing cycle is transformed to that of a manipulator. In addition, the pre- and post-processes are introduced to expedite the convergence of the Bi-RRT algorithm and to ensure the safe motion of the climbing robot near poles as well. The piecewise linear paths are smoothed by utilizing cubic B-spline curve fitting. The effectiveness and efficiency of the presented Bi-RRT algorithm for climbing motion planning are verified by simulations.

  8. Evolution, Interaction, and Intrinsic Properties of Dislocations in Intermetallics: Anisotropic 3D Dislocation Dynamics Approach

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Qian [Iowa State Univ., Ames, IA (United States)

    2008-01-01

    The generation, motion, and interaction of dislocations play key roles during the plastic deformation process of crystalline solids. 3D Dislocation Dynamics has been employed as a mesoscale simulation algorithm to investigate the collective and cooperative behavior of dislocations. Most current research on 3D Dislocation Dynamics is based on the solutions available in the framework of classical isotropic elasticity. However, due to some degree of elastic anisotropy in almost all crystalline solids, it is very necessary to extend 3D Dislocation Dynamics into anisotropic elasticity. In this study, first, the details of efficient and accurate incorporation of the fully anisotropic elasticity into 3D discrete Dislocation Dynamics by numerically evaluating the derivatives of Green's functions are described. Then the intrinsic properties of perfect dislocations, including their stability, their core properties and disassociation characteristics, in newly discovered rare earth-based intermetallics and in conventional intermetallics are investigated, within the framework of fully anisotropic elasticity supplemented with the atomistic information obtained from the ab initio calculations. Moreover, the evolution and interaction of dislocations in these intermetallics as well as the role of solute segregation are presented by utilizing fully anisotropic 3D dislocation dynamics. The results from this work clearly indicate the role and the importance of elastic anisotropy on the evolution of dislocation microstructures, the overall ductility and the hardening behavior in these systems.

  9. MRI findings in posterior disc prolapse associated with cervical fracture dislocation

    Energy Technology Data Exchange (ETDEWEB)

    Maeda, Go; Shiba, Keiichiro; Ueta, Takayoshi; Shirasawa, Kenzo; Ohta, Hideki; Mori, Eiji; Rikimaru, Shunichi; Hida, Shinichi; Tokunaga, Masami (Spinal Injuries Center, Fukuoka (Japan))

    1994-03-01

    Although disc injury is common in cervical spinal fractures the mechanism of disc herniation in cervical fracture dislocations is not known. This study evaluated the pathogenesis of disc hernia in cervical fracture dislocations. Twenty-two patients who underwent anterior and posterior spinal fixation were studied. Findings of preoperative magnetic resonance imaging (MRI) were compared with surgical findings. During surgery, cervical disk hernia were found in six patients (27 %), and the MRI finding of these patients were evaluated in detail. We concluded that the characteristic MRI findings of cervical disc hernia are as follows: (1) discontinuity of injured disc, (2) anterior indentation of spinal cord at the site of dislocated vertebral body, and (3) signal irregularity at the site of interspace between dislocated vertebral body and spinal cord. (author).

  10. Theoretical derivation of flow laws for quartz dislocation creep: Comparisons with experimental creep data and extrapolation to natural conditions using water fugacity corrections

    Science.gov (United States)

    Fukuda, Jun-ichi; Shimizu, Ichiko

    2017-08-01

    We theoretically derived flow laws for quartz dislocation creep using climb-controlled dislocation creep models and compared them with available laboratory data for quartz plastic deformation. We assumed volume diffusion of oxygen-bearing species along different crystallographic axes (//c, ⊥R, and ⊥c) of α-quartz and β-quartz, and pipe diffusion of H2O, to be the elementary processes of dislocation climb. The relationships between differential stress (σ) and strain rate (ɛ>˙) are written as ɛ>˙∝σ3Dv and ɛ>˙∝σ5Dp for cases controlled by volume and pipe diffusion, respectively, where Dv and Dp are coefficients of diffusion for volume and pipe diffusion. In previous experimental work, there were up to 1.5 orders of magnitude difference in the water fugacity values in experiments that used either gas-pressure-medium or solid-pressure-medium deformation apparatus. Therefore, in both the theories and flow laws, we included water fugacity effects as modified preexponential factors and water fugacity terms. Previous experimental data were obtained mainly in the β-quartz field and are highly consistent with the volume-diffusion-controlled dislocation creep models of β-quartz involving the water fugacity term. The theory also predicts significant effects for the transition of α-β quartz under crustal conditions. Under experimental pressure and temperature conditions, the flow stress of pipe-diffusion-controlled dislocation creep is higher than that for volume-diffusion-controlled creep. Extrapolation of the flow laws to natural conditions indicates that the contributions of pipe diffusion may dominate over volume diffusion under low-temperature conditions of the middle crust around the brittle-plastic transition zone.

  11. Electro-optical properties of dislocations in silicon and their possible application for light emitters

    Energy Technology Data Exchange (ETDEWEB)

    Arguirov, Tzanimir Vladimirov

    2007-10-14

    This thesis addresses the electro-optical properties of silicon, containing dislocations. The work demonstrates that dislocation specific radiation may provide a means for optical diagnostics of solar cell grade silicon. It provides insight into the mechanisms governing the dislocation recombination activity, their radiation, and how are they influenced by other defects present in silicon. We demonstrate that photoluminescence mapping is useful for monitoring the recombination activity in solar cell grade silicon and can be applied for identification of contaminants, based on their photoluminescence signatures. It is shown that the recombination at dislocations is strongly influenced by the presence of metals at the dislocation sites. The dislocation radiation activity correlates with their electrical activity. It is shown that the dislocation and band-to-band luminescence are essentially anti-correlated. {beta}FeSi{sub 2} precipitates, with a luminescence at 0.8 eV, were detected within the grains of block cast materials. They exhibit a characteristic feature of quantum dots, namely blinking. The second aspect of the thesis concerns the topic of silicon based light emitters for on-chip optical interconnects. The goal is an enhancement of sub-band-gap or band-to-band radiation by controlled formation of dislocation-rich areas in microelectronics-grade silicon as well as understanding of the processes governing such enhancement. For light emitters based on band-to-band emission it is shown, that internal quantum efficiency of nearly 2 % can be achieved, but the emission is essentially generated in the bulk of the wafer. On the other hand, light emitters utilizing the emission from dislocation-rich areas of a well localized wafer depth were explored. Three different methods for reproducible formation of a dislocation-rich region beneath the wafer surface were investigated and evaluated in view of their room temperature sub-band-gap radiation: (1) silicon implantation

  12. Distribution of distances between dislocations in different types of dislocation substructures in deformed Cu-Al alloys

    Energy Technology Data Exchange (ETDEWEB)

    Trishkina, L., E-mail: trishkina.53@mail.ru; Zboykova, N.; Koneva, N., E-mail: koneva@tsuab.ru; Kozlov, E. [Tomsk State University of Architecture and Building, 2 Solyanaya St., Tomsk, 634003 (Russian Federation); Cherkasova, T. [Tomsk State University of Architecture and Building, 2 Solyanaya St., Tomsk, 634003 (Russian Federation); National Research Tomsk Polytechnic University, 50 Lenin Ave., Tomsk, 634050 (Russian Federation)

    2016-01-15

    The aim of the investigation was the determination of the statistic description of dislocation distribution in each dislocation substructures component forming after different deformation degrees in the Cu-Al alloys. The dislocation structures were investigated by the transmission diffraction electron microscopy method. In the work the statistic description of distance distribution between the dislocations, dislocation barriers and dislocation tangles in the deformed Cu-Al alloys with different concentration of Al and test temperature at the grain size of 100 µm was carried out. It was established that the above parameters influence the dislocation distribution in different types of the dislocation substructures (DSS): dislocation chaos, dislocation networks without disorientation, nondisoriented and disoriented cells, in the walls and inside the cells. The distributions of the distances between dislocations in the investigated alloys for each DSS type formed at certain deformation degrees and various test temperatures were plotted.

  13. Distribution of distances between dislocations in different types of dislocation substructures in deformed Cu-Al alloys

    Science.gov (United States)

    Trishkina, L.; Cherkasova, T.; Zboykova, N.; Koneva, N.; Kozlov, E.

    2016-01-01

    The aim of the investigation was the determination of the statistic description of dislocation distribution in each dislocation substructures component forming after different deformation degrees in the Cu-Al alloys. The dislocation structures were investigated by the transmission diffraction electron microscopy method. In the work the statistic description of distance distribution between the dislocations, dislocation barriers and dislocation tangles in the deformed Cu-Al alloys with different concentration of Al and test temperature at the grain size of 100 µm was carried out. It was established that the above parameters influence the dislocation distribution in different types of the dislocation substructures (DSS): dislocation chaos, dislocation networks without disorientation, nondisoriented and disoriented cells, in the walls and inside the cells. The distributions of the distances between dislocations in the investigated alloys for each DSS type formed at certain deformation degrees and various test temperatures were plotted.

  14. Neglected dorsal dislocation of the scaphoid

    Directory of Open Access Journals (Sweden)

    Amaravati Rajkumar

    2009-01-01

    Full Text Available Isolated dislocation of the scaphoid is very rare. A 45-year old male, industrial worker reported two and half months after injury with wrist pain and swelling on the dorsum of left wrist. He was diagnosed as neglected dorsal dislocation of scaphoid. Proximal row carpectomy with capsular interposition was done stabilizing the distal carpus on the radius using Kirschner wires. At-12 months follow-up the patient had good wrist function and was satisfied with the outcome of the treatment. We hereby report this neglected dorsal dislocation of scaphoid in view of rarity and discuss the various options for management.

  15. Prismatic dislocation loops and concentric dislocation loops in HPHT-grown diamond single crystals

    International Nuclear Information System (INIS)

    Yin, L.-W.; Li, M.-S.; Zou, Z.-D.; Gong, Z.-G.; Hao, Z.-Y.

    2003-01-01

    As-grown diamond single crystals grown from Fe-Ni-C system under high temperature-high pressure were examined by transmission electron microscopy. There exist prismatic dislocation loops and concentric dislocation loops in the diamond, which are related to the nonequilibrium nature of the diamond synthesis process. The prismatic dislocation loops may be formed by vacancy condensation during rapid cooling from high temperature, and the Burgers vector of the dislocation is determined by diffraction contrast as 1/2 . Moire fringes formed by two overlapping (1 1 1) close-packed planes were used to study concentric dislocation loops. The concentric dislocation loops may be derived from thermal stress caused by the inclusions in the diamond, which cause a strain field due to the thermal contraction difference between the inclusions and the diamond during cooling from high temperature

  16. Effect of pre-existing immobile dislocations on the evolution of geometrically necessary dislocations during fatigue

    Science.gov (United States)

    Irastorza-Landa, Ainara; Grilli, Nicolò; Van Swygenhoven, Helena

    2017-07-01

    The role of pre-existing mobile and immobile dislocation densities on the evolution of geometrical necessary dislocation densities (GNDs) during cyclic fatigue in shear is studied using a continuum dislocation-based model incorporated in a crystal plasticity finite element scheme. Clusters with different immobile dislocation densities are implemented in a homogeneous medium containing a certain mobile dislocation density. It is found that whether GND walls are formed around the initial immobile cluster (or not) strongly depends on the absolute values of initial mobile dislocation density and on the ratio between mobile and immobile densities. The results are discussed in terms of the apparent GND densities experimentally obtained using Laue micro-diffraction.

  17. Traumatic hip dislocation; a South East Nigeria hospital experience ...

    African Journals Online (AJOL)

    Background: Hip dislocation is a relatively common orthopaedic emergency. The hip is an inherently stable joint and substantial force is required for dislocation to occur. Thus hip dislocation is said to follow motor vehicle accidents with more than 90% of hip dislocations being posterior. Thompson and Epstein grade I and II ...

  18. Quantifying the effect of hydrogen on dislocation dynamics: A three-dimensional discrete dislocation dynamics framework

    Science.gov (United States)

    Gu, Yejun; El-Awady, Jaafar A.

    2018-03-01

    We present a new framework to quantify the effect of hydrogen on dislocations using large scale three-dimensional (3D) discrete dislocation dynamics (DDD) simulations. In this model, the first order elastic interaction energy associated with the hydrogen-induced volume change is accounted for. The three-dimensional stress tensor induced by hydrogen concentration, which is in equilibrium with respect to the dislocation stress field, is derived using the Eshelby inclusion model, while the hydrogen bulk diffusion is treated as a continuum process. This newly developed framework is utilized to quantify the effect of different hydrogen concentrations on the dynamics of a glide dislocation in the absence of an applied stress field as well as on the spacing between dislocations in an array of parallel edge dislocations. A shielding effect is observed for materials having a large hydrogen diffusion coefficient, with the shield effect leading to the homogenization of the shrinkage process leading to the glide loop maintaining its circular shape, as well as resulting in a decrease in dislocation separation distances in the array of parallel edge dislocations. On the other hand, for materials having a small hydrogen diffusion coefficient, the high hydrogen concentrations around the edge characters of the dislocations act to pin them. Higher stresses are required to be able to unpin the dislocations from the hydrogen clouds surrounding them. Finally, this new framework can open the door for further large scale studies on the effect of hydrogen on the different aspects of dislocation-mediated plasticity in metals. With minor modifications of the current formulations, the framework can also be extended to account for general inclusion-induced stress field in discrete dislocation dynamics simulations.

  19. Evolution of dislocation structures following a change in loading conditions studied by in situ high resolution reciprocal space mapping

    DEFF Research Database (Denmark)

    Wejdemann, Christian

    or to a strain of 7% at a temperature of -196 ○C, and the samples were characterized by electron microscopy and mechanical tests. Transmission electron microscopy showed that the pre-deformation produced a characteristic dislocation cell structure consisting of regions with relatively high dislocation density...... the pre-deformation axis. In the X-ray diffraction experiments a technique was employed with which it is possible to obtain high-resolution reciprocal space maps from individual bulk grains. The high-resolution reciprocal space maps contain features related to the dislocation structure in the grains......: A spread-out ‘cloud’ of low intensity caused by diffraction from the dislocation walls and a number of sharp peaks of high intensity caused by diffraction from the individual subgrains. By acquiring reciprocal space maps at a number of different strain levels the evolution of the dislocation structures can...

  20. Posterior dislocation of the sternoclavicular joint leading to mediastinal compression.

    Science.gov (United States)

    Jougon, J B; Lepront, D J; Dromer, C E

    1996-02-01

    Dislocations of the sternoclavicular joint are uncommon, and the posterior variety have a potential for considerable morbidity. We report a case with compression of the vital structures within the superior mediastinum. It was a rugby player getting run over by the scrum. The mechanism was an indirect force exerted forward and laterally against the shoulder. The patient complained of pain and dysphagia. A systolic right cervical murmur was heard. Angiography was normal and esophagography showed extrinsic esophageal compression. Surgical reduction was performed because there was a slight pneumomediastinum on the computed tomography. This case report demonstrates the mechanism, complications, and treatment of such a lesion.

  1. Extracting dislocations and non-dislocation crystal defects from atomistic simulation data

    International Nuclear Information System (INIS)

    Stukowski, Alexander; Albe, Karsten

    2010-01-01

    We describe a novel method for extracting dislocation lines from atomistic simulation data in a fully automated way. The dislocation extraction algorithm (DXA) generates a geometric description of dislocation lines contained in an arbitrary crystalline model structure. Burgers vectors are determined reliably, and the extracted dislocation network fulfills the Burgers vector conservation rule at each node. All remaining crystal defects (grain boundaries, surfaces, etc), which cannot be represented by one-dimensional dislocation lines, are output as triangulated surfaces. This geometric representation is ideal for visualization of complex defect structures, even if they are not related to dislocation activity. In contrast to the recently proposed on-the-fly dislocation detection algorithm (ODDA) Stukowski (2010 Modelling Simul. Mater. Sci. Eng. 18 015012) the new method is extremely robust. While the ODDA was designed for a computationally efficient on-the-fly analysis, the DXA method enables a detailed analysis of dislocation lines even in highly distorted crystal regions, as they occur, for instance, close to grain boundaries or in dense dislocation networks

  2. Dislocations in the Kitaev honeycomb model

    Science.gov (United States)

    Petrova, Olga; Tchernyshyov, Oleg

    2013-03-01

    We study the effects of introducing dislocations into the Kitaev honeycomb model. In the gapped phase, dislocations are Z2 ``twist defects'' associated with the transmutation of electric and magnetic excitations, studied previously in the context of ZN rotor models. We show that each dislocation hosts one unpaired Majorana mode. As a consequence, twist defects have the statistics of Ising anyons. Because dislocations are confined, an additional phase is accumulated due to the change in system's energy during the braiding process. This means that the result of braiding can only be defined up to a phase. Therefore, twists are said to have projective non-Abelian statistics. Research was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award DE-FG02-08ER46544.

  3. Dislocation Enhancement of Seismic-Frequency Attenuation: Subgrain Boundary Diffusion and Triggered, Critical Emission of Dislocations

    Science.gov (United States)

    Cooper, R. F.; McCarthy, C.

    2012-12-01

    Combined compressional creep and (Young's-modulus) attenuation experiments on polycrystalline ice-I (200 ≤ T[K] ≤ 260; 3 ≤ d[μm] ≤ 500; σmean = 1MPa and Δσ = 0.16MPa applied in a frequency range 10-4 ≤ ν[Hz] ≤ 10-1) demonstrate the attenuation behavior associated with the seismic attenuation band and the "high-temperature background," i.e., a power-law response Q-1 ∝ ν-m with m ~ 0.33. This response has, in general, been associated with grain boundary sliding rate-limited by atomic diffusion [e.g., 1-3], a mechanism that is very sensitive to grain size. In our experiments, however, with a grain size variation ~102, the attenuation response is independent of grain size, to first order. Scrutiny of the physics suggests that the attenuation is effected primarily by diffusive relaxation of subgrain boundaries [4, 5], the size of which, in materials deforming by a dislocation mechanism (as is the ice in our experiments), is set by the deviatoric stress [6, 7]. Applying the diffusion-effected physics to the subgrain size matches the universal scaling [e.g., 3] for materials that are linear-viscoelastic. Our ice specimens, however, demonstrate modest non-linearity, resulting in greater attenuation than that associated with the diffusion process [cf. 8] and yet retain the power-law form for attenuation, including the same slope m. The result is consistent with "self-organized critical" behavior in dislocation emission [9, 10] and the physics overall can be understood via models of self-similar scaling of crystalline (effective) viscosity [e.g., 11]. The potential application to seismic studies is profound: for example, if the upper mantle of Earth is convecting via a dislocation-creep or dislocation-accommodated grain-boundary-sliding mechanism, then the attenuation response is related not to the grain size, but rather to the subgrain structure associated with the creep of the rock. Thus, seismic attenuation measurements may well be useful for

  4. Posterior atlantoaxial dislocation without odontoid fracture

    International Nuclear Information System (INIS)

    Chaudhary, Reema; Raut, Abhijit; Chaudhary, Kshitij; Metkar, Umesh; Rathod, Ashok; Sanghvi, Darshana

    2008-01-01

    We report a case of posterior atlantoaxial dislocation without a fracture of the odontoid in a 35-year-old woman. There have been nine reported cases of similar injury in the English literature. The integrity of the transverse ligament following posterior atlantoaxial dislocations has not been well documented in these reports. In the present case, MRI revealed an intact transverse ligament, which probably contributed to the stability of the C1-C2 complex following closed reduction. (orig.)

  5. Isolated Proximal Tibiofibular Dislocation during Soccer

    Directory of Open Access Journals (Sweden)

    Casey Chiu

    2015-01-01

    Full Text Available Proximal tibiofibular dislocations are rarely encountered in the Emergency Department (ED. We present a case involving a man presenting to the ED with left knee pain after making a sharp left turn on the soccer field. His physical exam was only remarkable for tenderness over the lateral fibular head. His X-rays showed subtle abnormalities of the tibiofibular joint. The dislocation was reduced and the patient was discharged from the ED with orthopedic follow-up.

  6. Dislocation of the proximal tibiofibular joint

    OpenAIRE

    Milankov Miroslav; Kecojević Vaso; Gvozdenović Nemanja; Obradović Mirko

    2013-01-01

    Introduction. Dislocation of the proximal tibiofibular joint is a rare injury. It occurs during a sports activity that includes rough twisting movements of the bent knee. The role of the proximal tibiofibular joint is to reduce torsional loads to the ankle, to distribute the bending moment of the outer side of tibia, and transfer the vertical load while standing. In the literature there is no larger series; only several cases of the proximal tibiofibular joint dislocation treated by dif...

  7. Posterior sternoclavicular dislocation: an American football injury

    DEFF Research Database (Denmark)

    Marker, L B; Klareskov, B

    1996-01-01

    Posterior dislocation of the sternoclavicular joint is uncommon, accounting for less than 0.1% of all dislocations. Since 1824 a little more than 100 cases have been reported, and the majority in the past 20 years. A review of published reports suggests that this injury is seen particularly in co...... in connection with American football. A typical case is described. The importance of this injury is that there is often a delay in diagnosis with potentially serious complications....

  8. Effect of crystal structure peculiarities of ageing alloys on dislocation structure during active deformation

    International Nuclear Information System (INIS)

    Travina, N.T.; Nikitin, A.A.; Zimina, L.N.

    1980-01-01

    On coarse-grain polycrystal samples of commercial KhN67MVTYu (EhP202), Kh60MVTYu (EhP487) and KhN60MKVYu (EhI661) alloys, aged under various conditions, studied are mechnanical properties after active deformation by extension at room temperature and dislocation structure corresponding to these structural states. Crystal and dislocation structures have been studied using electron microscope. In the alloys with mode--rate (13-14 v.%) quantity of γ' phase (KhN67MVTYu and KhN60MVTYu) at the stage of coherent-conjugated bond of particles with matrix deformation runs mainly according to the mechanism of cutting particles by separate dislocations; at the break of coherent bond - by bending of particles according to the Orovan mechanism or by their cutting with clusters of dislocations. At high volume part of particles of γ'-phase (40 v%, KhN60MKVYu alloy) the Orovan mechanism does not manifest itself in any of studied states. In this alloy at this stage of the break of the γ'-phase coherent bond with matrix in the result of ordered position of particles along the directions in matrix formed are interlayers free from particles on which strain is being mainly developed. Dislocation structure is compared with mechanical properties of the alloys

  9. MR findings of traumatic transient lateral dislocation of the patellae

    International Nuclear Information System (INIS)

    Lee, Jean Hwa; Kim, Sung Moon; Shin, Myung Jin; Seol, Hae Young; Ahn, Joong Mo

    2001-01-01

    To determine the magnetic resonance (MR) imaging characteristics of traumatic transient lateral dislocation of the patellae. In eight patients (6 males, 2 females, mean age : 22.4 years) in whom transient lateral dislocation of the patella was diagnosed, the distinctive MR imaging findings reflecting known injury mechanism were retrospectively analyzed with regard to bone contusion, chondral defect, fracture, loose body, joint effusion, and the associated soft tissue abnormalities. All of eight patients had bone contusions in the lateral femoral condyle and medial facet of the patella, while in five, chondral defects were present in this latter region. In three patients, fractures of the on lateral femoral condyle (n=2) and medial facet of the patella (n=3) were noted, and in three others loose bodies were noted. Noted. Joint effusion [simple effusion (n=4), lipohemarthrosis (n=3)] was observed in seven patients, and associated soft tissue injuries [to the medial patellar retinaculum (n=8), patellar tendon (n=2), and anterior cruciate ligament (n=1)] in eight. Patellar subluxation was found in seven. MR imaging is a useful technique for the diagnosis of traumatic lateral dislocation of the patella. The significant MR findings are bone contusion in the lateral femoral condyle and medial facet of the patella, chondral defect, fracture, joint effusion, injury to the medial patellar retinaculum, and patellar subluxation

  10. MR findings of traumatic transient lateral dislocation of the patellae

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jean Hwa; Kim, Sung Moon; Shin, Myung Jin [College of Medicine, Univ. of Ulsan, Seoul (Korea, Republic of); Seol, Hae Young [College of Medicine, Korea Univ., Seoul (Korea, Republic of); Ahn, Joong Mo [College of Medicine, Sungkyungkwan Univ., Seoul (Korea, Republic of)

    2001-10-01

    To determine the magnetic resonance (MR) imaging characteristics of traumatic transient lateral dislocation of the patellae. In eight patients (6 males, 2 females, mean age : 22.4 years) in whom transient lateral dislocation of the patella was diagnosed, the distinctive MR imaging findings reflecting known injury mechanism were retrospectively analyzed with regard to bone contusion, chondral defect, fracture, loose body, joint effusion, and the associated soft tissue abnormalities. All of eight patients had bone contusions in the lateral femoral condyle and medial facet of the patella, while in five, chondral defects were present in this latter region. In three patients, fractures of the on lateral femoral condyle (n=2) and medial facet of the patella (n=3) were noted, and in three others loose bodies were noted. Noted. Joint effusion [simple effusion (n=4), lipohemarthrosis (n=3)] was observed in seven patients, and associated soft tissue injuries [to the medial patellar retinaculum (n=8), patellar tendon (n=2), and anterior cruciate ligament (n=1)] in eight. Patellar subluxation was found in seven. MR imaging is a useful technique for the diagnosis of traumatic lateral dislocation of the patella. The significant MR findings are bone contusion in the lateral femoral condyle and medial facet of the patella, chondral defect, fracture, joint effusion, injury to the medial patellar retinaculum, and patellar subluxation.

  11. Ab initio modeling of interactions between screw dislocations and interstitial solutes in body-centered cubic transition metals

    International Nuclear Information System (INIS)

    Luthi, Berengere

    2017-01-01

    In order to improve our understanding of alloy plasticity, it is important to describe at the atomic scale the dislocation-solute interactions and their effect on the dislocation mobility. This work focuses on the body-centered cubic (BCC) transition metals in presence of interstitial solute atoms, in particular the Fe-C system. Using Density Functional Theory (DFT) calculations, the core structure of the screw dislocation of Burgers vector b=1/2<111> was investigated in iron in presence of boron, carbon, nitrogen and oxygen solute atoms, and in BCC metals from group 5 (V, Nb, Ta) and 6 (Mo, W) in presence of carbon solutes. A core reconstruction is evidenced in iron and group 6 metals, along with a strong attractive dislocation-solute interaction energy: the dislocation goes from easy to hard configuration where the solute atoms are at the center of trigonal prisms along the dislocation line. A different behavior is observed in group 5 metals, for which the most stable configuration for the carbon atom is an octahedral site in the vicinity of the dislocation, without any core reconstruction. This group tendency is linked to the structure of mono-carbides. Consequences of the strongly attractive dislocation-solute interactions in Fe(C) were then investigated. First the equilibrium segregation close to the dislocation core was studied using a mean-field model and Monte Carlo simulations. Over a wide temperature range, from 200 to 700 K, a strong segregation is predicted with every other prismatic site occupied by a carbon atom. Then, the mobility of the dislocation in presence of carbon atoms was investigated by modeling the double-kink mechanism with DFT, in relation with experimental data obtained with transmission electron microscopy. The activation energy obtained for this atomic scale mechanism is in good agreement with experimental values for the dynamic strain aging. (author) [fr

  12. Coupling between Re segregation and γ/γ′ interfacial dislocations during high-temperature, low-stress creep of a nickel-based single-crystal superalloy

    International Nuclear Information System (INIS)

    Huang, Ming; Cheng, Zhiying; Xiong, Jichun; Li, Jiarong; Hu, Jianqiao; Liu, Zhanli; Zhu, Jing

    2014-01-01

    The synergistic action of local elemental distribution, and in particular Re doping, with interfacial dislocations at the γ/γ′ interface is still one of the most considered and unclear issues during creep of nickel-based single-crystal superalloys. In order to investigate this problem, a detailed characterization of interfacial dislocations in a DD6 superalloy after creep loading for 12 h at high temperature and low stress was carried out using transmission electron microscopy and high-angle annular dark field scanning transmission electron microscopy techniques. In addition, the local elemental distribution near dislocation core regions was determined by energy dispersive X-ray spectroscopy (EDS) mapping. It was found for the first time that three types of interfacial protrusions are formed at the γ/γ′ interface after creep loading for 12 h under conditions of high temperature and low stress and demonstrated that the formation of these features originates from dislocation motion. Additionally, EDS mapping provides evidence for co-segregation of Re with Cr and Co at the tip of the protrusions. Based on this, a model concerning dislocation core structure and dislocation climb was proposed to explain the different morphology of the protrusions. The observations highlight the importance of the coupling between Re segregation and γ/γ′ interfacial dislocations for improving creep properties in nickel-based superalloys. The results of the study will be beneficial for the design of new high-temperature materials and for understanding the origin of the effect of Re additions in nickel-based single-crystal superalloys

  13. Incidence and Risk Factors for Upper Extremity Climbing Injuries in Indoor Climbers

    NARCIS (Netherlands)

    Van Middelkoop, M.; Bruens, M. L.; Coert, J. H.; Selles, R. W.; Verhagen, E.; Bierma-Zeinstra, S. M A; Koes, B. W.

    2015-01-01

    The purpose of this study was to describe the prevalence, incidence and risk factors for climbing-related injuries of the upper extremities in recreational climbers. A total of 426 recreational climbers were recruited from indoor climbing halls. The baseline questionnaire included questions on

  14. Does a video displaying a stair climbing model increase stair use in a worksite setting?

    Science.gov (United States)

    Van Calster, L; Van Hoecke, A-S; Octaef, A; Boen, F

    2017-08-01

    This study evaluated the effects of improving the visibility of the stairwell and of displaying a video with a stair climbing model on climbing and descending stair use in a worksite setting. Intervention study. Three consecutive one-week intervention phases were implemented: (1) the visibility of the stairs was improved by the attachment of pictograms that indicated the stairwell; (2) a video showing a stair climbing model was sent to the employees by email; and (3) the same video was displayed on a television screen at the point-of-choice (POC) between the stairs and the elevator. The interventions took place in two buildings. The implementation of the interventions varied between these buildings and the sequence was reversed. Improving the visibility of the stairs increased both stair climbing (+6%) and descending stair use (+7%) compared with baseline. Sending the video by email yielded no additional effect on stair use. By contrast, displaying the video at the POC increased stair climbing in both buildings by 12.5% on average. One week after the intervention, the positive effects on stair climbing remained in one of the buildings, but not in the other. These findings suggest that improving the visibility of the stairwell and displaying a stair climbing model on a screen at the POC can result in a short-term increase in both climbing and descending stair use. Copyright © 2017 The Royal Society for Public Health. Published by Elsevier Ltd. All rights reserved.

  15. Effects of sports climbing on muscle performance and balance for patients with multiple sclerosis

    DEFF Research Database (Denmark)

    Jolk, Christoph; Dalgas, Ulrik; Osada, Nani

    2015-01-01

    Background/Aims: The potential benefits of sports climbing for many diseases have not been investigated. The aim of this case series was to examine whether sports climbing is feasible and whether it can influence isometric muscle performance and balance in people with multiple sclerosis (MS). Met...

  16. The epidemiology of shoulder dislocations in Oslo.

    Science.gov (United States)

    Liavaag, S; Svenningsen, S; Reikerås, O; Enger, M; Fjalestad, T; Pripp, A H; Brox, J I

    2011-12-01

    There are few previous studies on the incidence of shoulder dislocation in the general population. The aim of the study was to report the incidence of acute shoulder dislocations in the capital of Norway (Oslo) in 2009. Patients of all ages living in Oslo, sustaining a dislocation of the glenohumeral joint, were identified using electronic diagnosis registers, patient protocols, radiological registers of the hospitals, and the Norwegian Patient Register (NPR). The overall incidence rate was 56.3 [95% confidence interval (CI) 50.2-62.4] per 100,000 person-years, with rates of 82.2 (95% CI 71.7-92.8) and 30.9 (95% CI 24.5-37.3) in men and women, respectively. The incidence of primary dislocations was 26.2 (95% CI 22.1-30.4). The overall incidence of shoulder dislocations in Oslo was higher than previously reported incidences. The incidence of primary dislocations was also higher than that in previously reported studies for the general population but it was close to the incidence reported in Malmø, Sweden. © 2011 John Wiley & Sons A/S.

  17. Generalized dynamics of moving dislocations in quasicrystals

    Energy Technology Data Exchange (ETDEWEB)

    Agiasofitou, Eleni; Lazar, Markus [Emmy Noether Research Group, Department of Physics, Darmstadt University of Technology, Hochschulstrasse 6, D-64289 Darmstadt (Germany); Kirchner, Helmut, E-mail: agiasofitou@mechanik.tu-darmstadt.d, E-mail: lazar@mechanik.tu-darmstadt.d, E-mail: kirchnerhok@hotmail.co [INM-Leibniz Institute for New Materials, Campus D22, D-66123 Saarbruecken (Germany)

    2010-12-15

    A theoretical framework for dislocation dynamics in quasicrystals is provided according to the continuum theory of dislocations. Firstly, we present the fundamental theory for moving dislocations in quasicrystals giving the dislocation density tensors and introducing the dislocation current tensors for the phonon and phason fields, including the Bianchi identities. Next, we give the equations of motion for the incompatible elastodynamics as well as for the incompatible elasto-hydrodynamics of quasicrystals. We continue with the derivation of the balance law of pseudomomentum thereby obtaining the generalized forms of the Eshelby stress tensor, the pseudomomentum vector, the dynamical Peach-Koehler force density and the Cherepanov force density for quasicrystals. The form of the dynamical Peach-Koehler force for a straight dislocation is obtained as well. Moreover, we deduce the balance law of energy that gives rise to the generalized forms of the field intensity vector and the elastic power density of quasicrystals. The above balance laws are produced for both models. The differences between the two models and their consequences are revealed. The influences of the phason fields as well as of the dynamical terms are also discussed.

  18. Atomic simulations of dislocation emission from Cu/Cu and Co/Cu grain boundaries

    International Nuclear Information System (INIS)

    Yuasa, Motohiro; Nakazawa, Takumi; Mabuchi, Mamoru

    2010-01-01

    Research highlights: → Co/Cu bicrystals have both E structures and stacking faults only in the Cu phase. → Dislocations tend to be emitted from the stacking faults in Co/Cu bicrystals. → Large disorder around the stacking faults accelerates the atomic shuffling. → Atomic shuffling behavior strongly affects dislocation emission in Co/Cu bicrystals. - Abstract: Molecular dynamics simulations of creep tests have been performed on Cu/Cu single-phase bicrystals and Co/Cu two-phase bicrystals to investigate the dislocation emission from grain boundaries. In the Co/Cu bicrystals, both E structures and stacking faults were generated only in the Cu grain near the boundary. Dislocations were emitted only from the stacking faults, not from the E structures, in the Co/Cu bicrystals. The stacking faults in the Co/Cu bicrystals did not necessarily enhance the dislocation emission as readily as those in the Cu/Cu bicrystals. The incoherence between Co and Cu gave rise to the complicated defect structures at and near the Co/Cu boundary, and thus distinctive atomic shuffling mechanisms occurred. This affected the dislocation emission behavior of the Co/Cu bicrystals.

  19. Control of dislocation morphology and lattice distortion in Na-flux GaN crystals

    Science.gov (United States)

    Takeuchi, S.; Mizuta, Y.; Imanishi, M.; Imade, M.; Mori, Y.; Sumitani, K.; Imai, Y.; Kimura, S.; Sakai, A.

    2017-09-01

    The dislocation morphology and lattice distortion, including the tilting and twisting of lattice planes, at the Na-flux GaN/seed-GaN interface were investigated using transmission electron microscopy (TEM) and position-dependent nanobeam X-ray diffraction (nanoXRD). The results revealed that the dislocation morphology and lattice distortion in Na-flux GaN at the initial growth stage are strongly influenced by the seed-GaN surface morphology and the growth mode of Na-flux GaN. From the TEM results, one can observe that the formation of dislocation-related etch pits (DREPs) on the seed-GaN surface and the three-dimensional (3D) growth mode for Na-flux GaN give rise to the bending and lateral propagation of dislocations penetrating from the seed-GaN to the Na-flux GaN. This simultaneously results in homogenization of the GaN crystal domain structure as confirmed by nanoXRD. The mechanism responsible for the bending and lateral propagation of dislocations by the formation of DREPs and the 3D growth mode for the Na-flux GaN and the correlation between the dislocation morphology and the lattice distortion are discussed on the basis of TEM and nanoXRD results.

  20. Formation of stacking faults and the screw dislocation-driven growth: a case study of aluminum nitride nanowires.

    Science.gov (United States)

    Meng, Fei; Estruga, Marc; Forticaux, Audrey; Morin, Stephen A; Wu, Qiang; Hu, Zheng; Jin, Song

    2013-12-23

    Stacking faults are an important class of crystal defects commonly observed in nanostructures of close packed crystal structures. They can bridge the transition between hexagonal wurtzite (WZ) and cubic zinc blende (ZB) phases, with the most known example represented by the "nanowire (NW) twinning superlattice". Understanding the formation mechanisms of stacking faults is crucial to better control them and thus enhance the capability of tailoring physical properties of nanomaterials through defect engineering. Here we provide a different perspective to the formation of stacking faults associated with the screw dislocation-driven growth mechanism of nanomaterials. With the use of NWs of WZ aluminum nitride (AlN) grown by a high-temperature nitridation method as the model system, dislocation-driven growth was first confirmed by transmission electron microscopy (TEM). Meanwhile numerous stacking faults and associated partial dislocations were also observed and identified to be the Type I stacking faults and the Frank partial dislocations, respectively, using high-resolution TEM. In contrast, AlN NWs obtained by rapid quenching after growth displayed no stacking faults or partial dislocations; instead many of them had voids that were associated with the dislocation-driven growth. On the basis of these observations, we suggest a formation mechanism of stacking faults that originate from dislocation voids during the cooling process in the syntheses. Similar stacking fault features were also observed in other NWs with WZ structure, such as cadmium sulfide (CdS) and zinc oxide (ZnO).

  1. [Anterior dislocation of the fibula resulting from surgical malreduction: a case report].

    Science.gov (United States)

    Wang, Z Y; Wu, X B

    2016-04-18

    Ankle joint fracture is one of the most common types of fracture. There are many researches on the injury mechanism, treatment principles and surgical techniques. A type of injury which combines posterior dislocation of fibula, known as the Bosworth injury, is relatively rare. In 1947, Bosworth first described this type of injury as an unusual ankle fracture dislocation with fixed posterior fracture dislocation of the distal part of the fibula. In this type of fracture, the proximal fibular shaft fragment locks behind the tibialis posterior tubercle. This rare ankle fracture variant is often not recognized in initial radiographs and requires a computed tomographic (CT) scan for verification. But there are already many reports, discussing the injury mechanism, treatment principles and surgical techniques. However, there are few reports of anterior dislocation of the fibula, caused by either injury or surgery. The mechanism of the injury is still not clear. This article reports a case of anterior dislocation of the fibula. We report a patient with left ankle open fracture (Lauge-Hansen pronation-external rotation stage III, Gustilo IIIA). Open reduction and internal fixation was done in the initial surgery, but ended up with poor reduction, resulting in fibula anterior dislocation, anterior dislocation of talus and tibia fibular dislocation. The fibula was dislocated anteriorly of the tibia, which rarely happened. The patient suffered severe ankle joint dysfunction. The second operation took out the original internal fixation, reduced the fracture, and reset the internal fixation. The function of ankle joint was improved obviously after operation. But because of the initial injury and the two operations, the soft tissue around the fracture was greatly damaged. 6 months after the second operation, and the fracture still not healed, so the bone graft was carried out in the third surgery. Two months after the third surgery, the function of the ankle was significantly

  2. Direct observation of gliding dislocations interactions with defects in irradiated niobium single crystals by means of the high voltage electronic microscopy (HVEM)

    International Nuclear Information System (INIS)

    Otero, M.P.

    1985-01-01

    The interactions of gliding dislocations with defects in irradiated niobium that result in the formation of dislocations channels. The effects in the mechanical behaviour of [941]- and [441]- oriented Nb single crystals due to oxygen addition, neutron and electron irradiation was observed either by macroscopic deformation in a Instron machine or 'in-situ' deformation in the HVEM-High Voltage Electron Microscope. Some specimens were irradiated at IPNS-Intense Pulsed Neutron Source, at 325 K, with 5 x 10 17 n/cm 2 , others were irradiated with electrons in the HVEM. The interactions between gliding dislocations with clusters point defects and dislocations were observed. The primary mechanism for removal of the clusters by the gliding dislocations was the 'sweeping' of the clusters along with the gliding dislocations. As to the point defects, they were 'swept' by the gliding dislocations and left as aligned loops close to the intersections of the gliding dislocations with the upper and lower specimen surfaces. For the illustration of this phenomena, a schematic drawing was made. The mechanism of 'bowing-out' interaction of dislocations with defect clusters was also observed. The reported anomalous slip observed to operate in the [941]- oriented Nb was also directly observed and a qualitive explanation along with a schematic drawing was proposed. This would explain the softenig observed after the yield stress in the [941]- oriented Nb deformed in the Instron machine. (Author) [pt

  3. Penyelesaian Masalah 8-Puzzle dengan Algoritma Steepest-Ascent Hill Climbing

    Directory of Open Access Journals (Sweden)

    David Abraham

    2016-03-01

    Full Text Available 8 puzzle merupakan salah satu implementasi dari Artificial Intelegence. Dalam proses penyelesaiannya banyak terdapat algoritma-algoritma pencarian yang dapat diterapkan. Solusi 8 puzzle akan lebih cepat diperoleh jika digunakan prinsip array dengan variasi algoritma Steepest-Ascent Hill Climbing (Hill Climbing dengan memilih kemiringan yang paling tajam / curam dengan parameter heuristik posisi yang benar dan heuristik jarak serta dikombinasikan dengan LogList sebagai penyimpanan state state yang pernah dilalui untuk menanggulangi permasalah pada algoritma hill climbing itu sendiri dan terhindar dari looping state yang pernah dilalui. Metode-metode yang termasuk ke dalam teknik pencarian yang berdasarkan pada fungsi heuristik salah satu diantaranya adalah Hill Climbing, Best First Search, A* (A Bintang. Loglist merupakan tempat penyimpanan setiap kunjungan dari state-state puzzle yang telah dilakukan untuk menghindari looping atau pengulangan terhadap state yang pernah dilalui. Untuk menanggulangi permasalahan pada SteepestAscent Hill Climbing.

  4. Study of loop-loop and loop-edge dislocation interactions in bcc iron

    DEFF Research Database (Denmark)

    Osetsky, Y.N.; Bacon, D.J.; Gao, F.

    2000-01-01

    Recent theoretical calculations and atomistic computer simulations have shown that one-dimensional glissile clusters of self-interstitial atoms (SIAs) play an important role in the evolution of microstructure in metals and alloys under cascade damage conditions. Recently, it has been proposed...... that the evolution of heterogeneities such as dislocation decoration and rafts has serious impacts on the mechanical properties on neutron-irradiated metals. In the present work, atomic-scale computer modelling (ASCM) has been applied to study the mechanisms for the formation of such microstructure in bcc iron....... It is shown that glissile clusters with parallel Burgers vectors interact strongly and can form extended immobile complexes, i.e., rafts. Similar attractive interaction exists between dislocation loops and an edge dislocation. These two mechanisms may be responsible for the formation of extended complexes...

  5. Normal-stress coefficients and rod climbing in colloidal dispersions

    Science.gov (United States)

    Farage, T. F. F.; Reinhardt, J.; Brader, J. M.

    2013-10-01

    We calculate tractable microscopic expressions for the low-shear normal-stress coefficients of colloidal dispersions. Although restricted to the low rate regime, the presented formulas are valid for all volume fractions below the glass transition and for any interaction potential. Numerical results are presented for a system of colloids interacting via a hard-core attractive Yukawa potential, for which we explore the interplay between attraction strength and volume fraction. We show that the normal-stress coefficients exhibit nontrivial features close to the critical point and at high volume fractions in the vicinity of the reentrant glass transition. Finally, we exploit our formulas to make predictions about rod-climbing effects in attractive colloidal dispersions.

  6. On the static structural design of climbing robots: part 2.

    Science.gov (United States)

    Ahmed, Ausama Hadi; Menon, Carlo

    This manuscript is the second of two parts of a work investigating optimal configurations of legged climbing robots while loitering on vertical surfaces. In this Part 2, a structural analysis based on the finite element method, specifically the stiffness method, is performed to address the problem. Parameters that are investigated in this Part 2 include the inclination of both the body and the legs of the robot. Outcomes of the performed study are validated by analyzing the posture of 150 ants when loitering on vertical surfaces. The obtained validation ensures the predictions of the developed structural model are correct and can be used to identify optimal configurations of legged robots when loitering on vertical surfaces.

  7. Mechanical behavior and related microstructural aspects of a nano-lamellar TiAl alloy at elevated temperatures

    International Nuclear Information System (INIS)

    Klein, T.; Usategui, L.; Rashkova, B.; Nó, M.L.; San Juan, J.; Clemens, H.; Mayer, S.

    2017-01-01

    Advanced intermetallic γ-TiAl based alloys, which solidify via the disordered β phase, such as the TNM + alloy, are considered as most promising candidates for structural applications at high temperatures in aero and automotive industries, where they are applied increasingly. Particularly creep resistant microstructures required for high-temperature application, i.e. fine fully lamellar microstructures, can be attained via two-step heat-treatments. Thereby, an increasing creep resistance is observed with decreasing lamellar interface spacing. Once lamellar structures reach nano-scaled dimensions, deformation mechanisms are altered dramatically. Hence, this study deals with a detailed characterization of the elevated temperature deformation phenomena prevailing in nano-lamellar TiAl alloys by the use of tensile creep experiments and mechanical spectroscopy. Upon creep exposure, microstructural changes occur in the lamellar structure, which are analyzed by the comparative utilization of X-ray diffraction, scanning and transmission electron microscopy as well as atom probe tomography. Creep activation parameters determined by mechanical characterization suggest the dominance of dislocation climb by a jog-pair formation process. The dislocations involved in deformation are, in nano-lamellar TiAl alloys, situated at the lamellar interfaces. During creep exposure the precipitation of β o phase and ζ-silicide particles is observed emanating from the α 2 phase, which is due to the accumulation of Mo and Si at lamellar interfaces.

  8. Deformation mechanisms in a precipitation-strengthened ferritic superalloy revealed by in situ neutron diffraction studies at elevated temperatures

    International Nuclear Information System (INIS)

    Huang, Shenyan; Gao, Yanfei; An, Ke; Zheng, Lili; Wu, Wei; Teng, Zhenke; Liaw, Peter K.

    2015-01-01

    The ferritic superalloy Fe–10Ni–6.5Al–10Cr–3.4Mo strengthened by ordered (Ni,Fe)Al B2-type precipitates is a candidate material for ultra-supercritical steam turbine applications above 923 K. Despite earlier success in improving its room-temperature ductility, the creep resistance of this material at high temperatures needs to be further improved, which requires a fundamental understanding of the high-temperature deformation mechanisms at the scales of individual phases and grains. In situ neutron diffraction has been utilized to investigate the lattice strain evolution and the microscopic load-sharing mechanisms during tensile deformation of this ferritic superalloy at elevated temperatures. Finite-element simulations based on the crystal plasticity theory are employed and compared with the experimental results, both qualitatively and quantitatively. Based on these interphase and intergranular load-partitioning studies, it is found that the deformation mechanisms change from dislocation slip to those related to dislocation climb, diffusional flow and possibly grain boundary sliding, below and above 873 K, respectively. Insights into microstructural design for enhancing creep resistance are also discussed

  9. Features and functionality of speed and power capabilities of elite climbers and various types of rock climbing

    OpenAIRE

    O.A. Ryepko

    2013-01-01

    The purpose of this study was comparative and functional characterization of speed- force readiness elite athletes - representatives of climbing to the complexity, speed and climbers. The study involved 26 athletes: 10 masters of sports of international class (speed climbing), 10 masters of sports of international class (climbing difficulty), 6 world-class climbers. The age of the athletes was 19-22 years. Found that the different types of rock climbing have different requirements for the dev...

  10. Modeling of the mechanical behavior of austenitic stainless steels under pure fatigue and fatigue relaxation loadings

    International Nuclear Information System (INIS)

    Hajjaji-Rachdi, Fatima

    2015-01-01

    Austenitic stainless steels are potential candidates for structural components of sodium-cooled fast neutron reactors. Many of these components will be subjected to cyclic loadings including long hold times (1 month) under creep or relaxation at high temperature. These hold times are unattainable experimentally. The aim of the present study is to propose mechanical models which take into account the involved mechanisms and their interactions during such complex loadings. First, an experimental study of the pure fatigue and fatigue-relaxation behavior of 316L(N) at 500 C has been carried out with very long hold times (10 h and 50 h) compared with the ones studied in literature. Tensile tests at 600 C with different applied strain rates have been undertaken in order to study the dynamic strain ageing phenomenon. Before focusing on more complex loadings, the mean field homogenization approach has been used to predict the mechanical behavior of different FCC metals and alloys under low cycle fatigue at room temperature. Both Hill-Hutchinson and Kroener models have been used. Next, a physically-based model based on dislocation densities has been developed and its parameters measured. The model allows predictions in a qualitative agreement with experimental data for tensile loadings. Finally, this model has been enriched to take into account visco-plasticity, dislocation climb and interaction between dislocations and solute atoms, which are influent during creep-fatigue or fatigue relaxation at high temperature. The proposed model uses three adjustable parameters only and allows rather accurate prediction of the behavior of 316L(N) steel under tensile loading and relaxation. (author) [fr

  11. Dislocation Dynamics in Al-Li Alloys. Mean Jump Distance and Activation Length of Moving Dislocations

    NARCIS (Netherlands)

    Hosson, J.Th.M. De; Huis in 't Veld, A.; Tamler, H.; Kanert, O.

    1984-01-01

    Pulsed nuclear magnetic resonance proved to be a complementary new technique for the study of moving dislocations in Al-Li alloys. The NMR technique, in combination with transmission electron microscopy and strain-rate change experiments have been applied to study dislocation motion in Al-2.2 wt% Li

  12. Evaluation of traumatic atlantooccipital dislocations.

    Science.gov (United States)

    Lee, C; Woodring, J H; Goldstein, S J; Daniel, T L; Young, A B; Tibbs, P A

    1987-01-01

    The diagnosis of traumatic atlantooccipital dislocation (AOD) from the cross-table lateral radiograph is difficult because of problems in demonstrating the complex anatomy of this area and the intricate radiographic methods used to diagnose AOD. Although CT or polytomography seem to be the most accurate diagnostic methods, it is often the lateral radiograph from which the diagnosis and further decisions are made. To determine both the best radiographic method for diagnosing AOD from the lateral radiograph and the role of CT and tomography in the diagnosis of AOD, the literature was reviewed concerning how the diagnosis of AOD has been obtained. In addition, the Wholey dens-basion line, the Powers ratio, the Dublin method of diagnosing AOD, and measurement of the atlantooccipital joint width were applied to 12 cases of traumatic AOD; and the Wholey dens-basion line and the Powers ratio were determined in 100 normal adults and 50 normal children. An alternative plain radiographic method for diagnosing AOD was developed, called the X-line method. This was the most accurate of the methods tested, correctly diagnosing AOD in 75% of cases. The Wholey dens-basion line and direct measurement of the atlantooccipital joint width were each correct in 50% of cases, the Powers ratio in 33% of cases, and the Dublin method in only 25% of cases. Ultimately, either CT or polytomography should provide the definitive diagnosis. In this regard high-resolution CT with reformatted coronal and sagittal images generated from 2-mm thin axial slices appeared to have the most promise as the first study of choice.

  13. Rock climbing and acute emotion regulation in patients with major depressive disorder in the context of a psychological inpatient treatment: a controlled pilot trial

    Directory of Open Access Journals (Sweden)

    Kleinstäuber M

    2017-08-01

    Full Text Available Maria Kleinstäuber,1,2 Merle Reuter,3 Norbert Doll,4 Andreas J Fallgatter4 1Division of Clinical Psychology and Psychotherapy, Faculty of Psychology, Philipps University, Marburg, Germany; 2Department of Psychological Medicine, School of Medicine, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand; 3Department of Educational Psychology, Faculty of Psychology, Eberhard Karls University, Tübingen, Germany, 4Department of General Psychiatry and Psychotherapy, University Hospital for Psychiatry and Psychotherapy, Eberhard Karls University, Tübingen, Germany Background: Major depressive disorder is characterized by deficits in emotion regulation. This study examined associations between rock climbing and acute emotion regulating effects in patients with major depression. Patients and methods: In a nonrandomized, controlled study, 40 major depressive disorder inpatients were assigned to either a climbing session (n=20 or a relaxation session (n=20. Positive and negative affect, depressiveness, and coping emotions were assessed immediately before and after the session. Results: Mixed analyses of variance and covariance revealed significant time × group interaction effects for all assessed outcomes (p≤0.012: positive affect and coping emotions significantly increased and negative affect and depressiveness significantly decreased after the climbing session (1.04≤ Cohen’s d ≤1.30, in contrast to a relaxation session (0.16≤ Cohen’s d ≤0.36. Conclusion: The results show that rock climbing is associated with acute emotion regulatory effects. These findings have to be replicated with a randomized design, and future research should pay attention to possible mechanisms of rock climbing in regard to emotion regulation. Keywords: physical activity, controlled trial, relaxation, inpatient treatment

  14. The effect of ladder-climbing exercise on atrophy/hypertrophy-related myokine expression in middle-aged male Wistar rats.

    Science.gov (United States)

    Jung, Suryun; Ahn, Nayoung; Kim, Sanghyun; Byun, Jayoung; Joo, Youngsik; Kim, Sungwook; Jung, Yeunho; Park, Solee; Hwang, Ilseon; Kim, Kijin

    2015-11-01

    We investigated the change in myokine expression related to hypertrophy (IL-4, IL-6, IL-10) and atrophy (TNF-α, NFκB, IL-1β) in middle-aged rats after resistance exercise with ladder climbing. 50- and 10-week-old male Wistar rats were randomly assigned to two groups: the sedentary and exercise groups. The exercise groups underwent a ladder-climbing exercise for 8 weeks. While the tibialis anterior muscle mass in the young group significantly increased after the ladder-climbing exercise, the middle-aged group did not show any changes after undergoing the same exercise. To understand the molecular mechanism causing this difference, we analyzed the change in hypertrophy- and atrophy-related myokine levels from the tibialis anterior muscle. After 8 weeks of ladder-climbing exercise, the IL-4 and IL-10 protein levels did not change. However, the IL-6 level significantly increased after exercise training, but the amount of increase in the young training group was higher than in the middle-aged training group. IL-1β and TNF-α as well as NFκB protein levels were significantly higher in the middle-aged group than in the young group. Except for TNF-α, exercise training did not affect IL-1β and NFκB protein levels. The TNF-α level significantly decreased in the middle-aged exercise training group. AMPK and PGC-1α levels also significantly increased after exercise training, but there was no difference between age-related groups. Therefore, 8-week high-intensity exercise training using ladder climbing downregulates the skeletal muscle production of myokine involved in atrophy and upregulates hypertrophic myokine. However, the extent of these responses was lower in the middle-aged than young group.

  15. The peculiar effect of forest dislocations on single twin layer development in zinc and beryllium single crystals

    International Nuclear Information System (INIS)

    Lavrentev, F.F.; Bosin, M.E.

    1978-01-01

    This is an investigation of the effect of different types of forest dislocation on the rate of twin layer broadening, Vsub(n), in zinc and beryllium crystals, and on the velocity of the twinning dislocation movement, Vsub(t), in zinc crystals under the action of a constant external shear stress. Increasing the forest basal dislocation density, rhosub(b), was found to result in increasing Vsub(n) and reducing Vsub(t), while increasing the forest pyramidal dislocation density, rhosub(p), causes Vsub(n) to decrease. An analysis in terms of crystal geometry shows that the dualism of the influence of the basal dislocations stems from the fact that they behave as twinning dislocation sources whose density, increasing with rhosub(b) leads to higher Vsub(n). The decrease in the effective stress, tausup(*), with increasing rhosub(b) is estimated. An analysis of the experimental data yielded the relation Vsub(t)(tausup(*)) and an estimate of the activation volume, which amounted to 6 x 10 -21 cm 3 . The close coincidence of the activation volumes as obtained from Vsub(t)(tausup(*)) and Vsub(n)(tau) suggests that the rate-controlling mechanism of the twin layer development in zinc crystals with large forest basal dislocation density is the twinning dislocation inhibition. In Be crystals, the increasing Vsub(n) effect is observed during untwinning. In Be twinned crystals, electron microscopy revealed twinning dislocations with a density of about 10 5 cm -1 at the twin boundaries and a large forest basal dislocation density inside the twin (ca. 10 8 cm -2 ). (Auth.)

  16. Incidence of and risk factors for traumatic anterior shoulder dislocation: an epidemiologic study in high-school rugby players.

    Science.gov (United States)

    Kawasaki, Takayuki; Ota, Chihiro; Urayama, Shingo; Maki, Nobukazu; Nagayama, Masataka; Kaketa, Takefumi; Takazawa, Yuji; Kaneko, Kazuo

    2014-11-01

    The incidence of reinjuries due to glenohumeral instability and the major risk factors for primary anterior shoulder dislocation in youth rugby players have been unclear. The purpose of this study was to investigate the incidence, mechanisms, and intrinsic risk factors of shoulder dislocation in elite high-school rugby union teams during the 2012 season. A total of 378 male rugby players from 7 high-school teams were investigated by use of self-administered preseason and postseason questionnaires. The prevalence of a history of shoulder dislocation was 14.8%, and there were 21 events of primary shoulder dislocation of the 74 overall shoulder injuries that were sustained during the season (3.2 events per 1000 player-hours of match exposure). During the season, 54.3% of the shoulders with at least one episode of shoulder dislocation had reinjury. This study also indicated that the persistence of glenohumeral instability might affect the player's self-assessed condition, regardless of the incidence during the current season. By a multivariate logistic regression method, a history of shoulder dislocation on the opposite side before the season was found to be a risk factor for contralateral primary shoulder dislocation (odds ratio, 3.56; 95% confidence interval, 1.27-9.97; P = .02). High-school rugby players with a history of shoulder dislocation are not playing at full capacity and also have a significant rate of reinjury as well as a high risk of dislocating the other shoulder. These findings may be helpful in deciding on the proper treatment of primary anterior shoulder dislocation in young rugby players. Copyright © 2014 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.

  17. Hybrid Dislocated Control and General Hybrid Projective Dislocated Synchronization for Memristor Chaotic Oscillator System

    Directory of Open Access Journals (Sweden)

    Junwei Sun

    2014-01-01

    Full Text Available Some important dynamical properties of the memristor chaotic oscillator system have been studied in the paper. A novel hybrid dislocated control method and a general hybrid projective dislocated synchronization scheme have been realized for memristor chaotic oscillator system. The paper firstly presents hybrid dislocated control method for stabilizing chaos to the unstable equilibrium point. Based on the Lyapunov stability theorem, general hybrid projective dislocated synchronization has been studied for the drive memristor chaotic oscillator system and the same response memristor chaotic oscillator system. For the different dimensions, the memristor chaotic oscillator system and the other chaotic system have realized general hybrid projective dislocated synchronization. Numerical simulations are given to show the effectiveness of these methods.

  18. In situ observation by the high-voltage electron microscope of dynamic dislocation behaviour in the processes of tensile deformation and fatigue

    International Nuclear Information System (INIS)

    Imura, T.; Yukawa, N.; Saka, H.; Nohara, A.; Ishikawa, I.; Kamino, T.

    1975-01-01

    To investigate the dynamic properties of dislocations, a new direct method was developed by using a high-voltage electron microscope (HVEM). The motion of edge and screw dislocations was observed in thick foil specimens of Fe, Fe-3%Si, 18-8 stainless steel, and A1 being stretched at various temperatures with a new straining device in HVEM operated at 500 to 1000 kV. The dislocation motions were recorded continuously on video tape with the aid of an image intensifier, and the corresponding stress-strain curve of the specimen under observation was also recorded simultaneously. Newly developed tensile testing devices and a fatigue stage are introduced, all of which can be mounted on a goniometer stage and are equipped with high-sensitivity strain gauges. The velocity of dislocations as a function of applied stress, the types of dislocation sources and mechanism of dislocation multiplication, the dynamic crossing-over of dislocations, the information on the elemental dislocation mechanisms of yielding, work hardening, crack propagation, and fatigue are obtained. The effects of specimen thickness and high-energy electron bombardment on the dislocation motion are discussed to testify to the validity of the result obtained. (author)

  19. Fabrics and deformational mechanisms in the high-pressure granulite of the Bacariza Formation (Cabo Ortegal Complex, NW Spain); Fabricas y mecanismos deformacionales en las granulitas de alta presion de la Formacion Bacariza (Complejo de Cabo Ortegal, NO de Espana)

    Energy Technology Data Exchange (ETDEWEB)

    Puelles, P.

    2009-07-01

    In the Cabo Ortegal Complex, mylonitic high-pressure granulites occur at the contacts between the HP granulitic Bacariza Formation and the adjacent units. This mylonitic stage is associated with the initial exhumation of the complex. The petrographic, microstructural and crystallographic analysis of the main constituent minerals in these rocks might provide valuable information on the deformation mechanisms operative at depth. Garnet accommodated part of the deformation by dislocation creep and rigid rotation, augite underwent dislocation creep accompanied by mass transfer and anisotropic growth while plagioclase, in turn, suffered dynamic subgrain rotation-recrystallization and climb-accommodated dislocation creep. Quartz fabrics developed under at least amphibolite-facies conditions. The shear sense criteria are consistent with a top-to-the-NE displacement of the hanging wall blocks. During their ascent to the surface, a static amphibolite-facies retrogressive stage was followed by plastic deformation accommodation under green schist- to lower amphibolite facies conditions. Deformation during the latest stages of exhumation was characterized by micro fracturing and seismic activity in conditions of high differential stresses and strain rates. (Author) 52 refs.

  20. Dislocations, the elastic energy momentum tensor and crack propagation

    International Nuclear Information System (INIS)

    Lung, Chi-wei

    1979-07-01

    Based upon dislocation theory, some stress intensity factors can be calculated for practical cases. The results obtained by this method have been found to agree fairly well with the results obtained by the conventional fracture mechanics. The elastic energy momentum tensor has been used to calculate the force acting on the crack tip. A discussion on the kinetics of migration of impurities to the crack tip was given. It seems that the crack tip sometimes may be considered as a singularity in an elastic field and the fundamental law of classical field theory is applicable on the problem in fracture of materials. (author)

  1. Local Variability of the Peierls Barrier of Screw Dislocations in Ta-10W.

    Energy Technology Data Exchange (ETDEWEB)

    Foiles, Stephen M. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2017-10-01

    It is well know that the addition of substitutional elements changes the mechanical behavior of metals, a effect referred to solid solution hardening. For body-centered-cubic (BCC) metals, screw dislocation play a key role in the mechanical properties. Here the detailed modification of the Peierls barrier for screw dislocation motion in Ta with W substitutional atoms is computing using density functional theory (DFT). A reduced order model (ROM) of the influence of W substitution on the Peierls barrier is developed. The mean field change in the Peierls barrier for a Ta10W alloy is determined and shown to be larger than anticipated based on simple elasticity considerations. The ROM could be used in future calculations to determine the local variability of the Peierls barrier and the resultant influence on the motion of screw dislocation in this alloy.

  2. Stacking fault domains as sources of a-type threading dislocations in III-nitride heterostructures

    Science.gov (United States)

    Smalc-Koziorowska, J.; Bazioti, C.; Albrecht, M.; Dimitrakopulos, G. P.

    2016-02-01

    A mechanism for the nucleation of a-type threading dislocation half-loops from basal stacking faults in wurtzite III-nitride heterostructures is presented. Transmission electron microscopy observations, in conjunction with topological and strain analysis, show that there are two possible configurations of closed domains comprising basal stacking faults of I1 type. It is shown that the lattice dislocation may emanate when the sphalerite structural units of the stacking faults in the closed domain are oriented in a parallel manner. The closed domain configurations do not introduce any shift on the basal planes, resulting in zero defect content along the growth direction. The stacking fault domains are hexagonal, with sides along the ⟨ 10 1 ¯ 0 ⟩ directions, and the threading dislocation half loops nucleate at the line nodes. The mechanism was found to be operational in multiple III-nitride systems.

  3. In Situ TEM Study of Interaction between Dislocations and a Single Nanotwin under Nanoindentation.

    Science.gov (United States)

    Wang, Bo; Zhang, Zhenyu; Cui, Junfeng; Jiang, Nan; Lyu, Jilei; Chen, Guoxin; Wang, Jia; Liu, Zhiduo; Yu, Jinhong; Lin, Chengte; Ye, Fei; Guo, Dongming

    2017-09-06

    Nanotwinned (nt) materials exhibit excellent mechanical properties, and have been attracting much more attention of late. Nevertheless, the fundamental mechanism of interaction between dislocations and a single nanotwin is not understood. In this study, in situ transmission electron microscopy (TEM) nanoindentation is performed, on a specimen of a nickel (Ni) alloy containing a single nanotwin of 89 nm in thickness. The specimen is prepared using focused ion beam (FIB) technique from an nt surface, which is formed by a novel approach under indentation using a developed diamond panel with tips array. The stiffness of the specimen is ten times that of the pristine counterparts during loading. The ultrahigh stiffness is attributed to the generation of nanotwins and the impediment of the single twin to the dislocations. Two peak loads are induced by the activation of a new slip system and the penetration of dislocations over the single nanotwin, respectively. One slip band is parallel to the single nanotwin, indicating the slip of dislocations along the nanotwin. In situ TEM observation of nanoindentation reveals a new insight for the interaction between dislocations and a single nanotwin. This paves the way for design and preparation of high-performance nt surfaces of Ni alloys used for aircraft engines, gas turbines, turbocharger components, ducts, and absorbers.

  4. Determination of the extinction factor in function of the density of dislocations; Determinacion del factor de extincion en funcion de la densidad de dislocaciones

    Energy Technology Data Exchange (ETDEWEB)

    Macias B, L.R

    1991-12-15

    There are exist three basic types of crystalline lattice defects: point, line (or dislocations) and surface defects. Such defects may be incorporated intentionally to produce desired mechanical and physical properties. This report presents a FORTRAN language program to calculate the extinction factor in samples of polycrystalline copper as function of the dislocations density. (Author)

  5. Interactions between Lattice Dislocations and Grain Boundaries in Ni3Al Investigated by Means of In Situ TEM and Computer Modelling Experiments

    NARCIS (Netherlands)

    Pestman, B.J.; Hosson, J.Th.M. De

    1992-01-01

    The interaction between lattice dislocations and grain boundaries in Ni3Al has been investigated by means of in situ TEM deformation experiments. The interaction between screw dislocations and a coherent twin boundary could be analyzed in detail. The interaction mechanism found experimentally was

  6. Risk factors for injury in sport climbing and bouldering: a systematic review of the literature.

    Science.gov (United States)

    Woollings, Kaikanani Y; McKay, Carly D; Emery, Carolyn A

    2015-09-01

    Rock climbing is an increasingly popular sport worldwide, as a recreational activity and a competitive sport. Several disciplines including sport climbing and bouldering have developed, each employing specific movements and techniques, leading to specific injuries. To examine risk factors and prevention measures for injury in sport climbing and bouldering, and to assess the methodological quality of existing studies. 12 electronic databases and several other sources were searched systematically using predetermined inclusion and exclusion criteria. Eligible articles were peer-reviewed, based on primary research using original data; outcome measures included injury, morbidity or mortality in rock climbing, and included one or more potential risk factor or injury prevention strategy. Two independent reviewers assessed the methodology of research in each study using the Downs and Black Quality Index. The data extracted is summarised, and appraisals of the articles are presented with respect to the quality of evidence presented. 19 studies met the inclusion criteria, and introduced 35 possible risk factors or injury prevention measures in climbing. Age, increasing years of climbing experience, highest climbing grade achieved (skill level), high climbing intensity score (CIS) and participating in lead climbing are potential risk factors. Results regarding injury prevention measures remain inconclusive. This field is relatively new and, as such, the data are not as robust as for more established sports with a larger research foundation. The key need is establishing modifiable risk factors using prospective studies and high quality methodology, such that injury prevention strategies can be developed. The CIS may be a useful measure in this field of research. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

  7. Rare Inferior Shoulder Dislocation (Luxatio Erecta)

    Science.gov (United States)

    Cift, Hakan; Soylemez, Salih; Demiroglu, Murat; Ozkan, Korhan; Ozden, Vahit Emre; Ozkut, Afsar T.

    2015-01-01

    Although shoulder dislocations have been seen very frequently, inferior dislocation of shoulder constitutes only 0.5% of all shoulder dislocations. We share our 4 patients with luxatio erecta and present their last clinical control. 2 male and 2 female Caucasian patients were diagnosed as luxatio erecta. Patients' ages were 78, 62, 65, and 76. All patients' reduction was done by traction-abduction and contour traction maneuver in the operating room. The patients had no symptoms and no limitation of range of motion of their shoulder at their last control. Luxatio erecta is seen rarely, and these patients may have neurovascular injury. These patients should be carefully examined and treated by the orthopaedic and traumatology surgeons. PMID:25883820

  8. Rare Inferior Shoulder Dislocation (Luxatio Erecta

    Directory of Open Access Journals (Sweden)

    Hakan Cift

    2015-01-01

    Full Text Available Although shoulder dislocations have been seen very frequently, inferior dislocation of shoulder constitutes only 0.5% of all shoulder dislocations. We share our 4 patients with luxatio erecta and present their last clinical control. 2 male and 2 female Caucasian patients were diagnosed as luxatio erecta. Patients’ ages were 78, 62, 65, and 76. All patients’ reduction was done by traction-abduction and contour traction maneuver in the operating room. The patients had no symptoms and no limitation of range of motion of their shoulder at their last control. Luxatio erecta is seen rarely, and these patients may have neurovascular injury. These patients should be carefully examined and treated by the orthopaedic and traumatology surgeons.

  9. Void growth suppression by dislocation impurity atmospheres

    International Nuclear Information System (INIS)

    Weertman, J.; Green, W.V.

    1976-01-01

    A detailed calculation is given of the effect of an impurity atmosphere on void growth under irradiation damage conditions. Norris has proposed that such an atmosphere can suppress void growth. The hydrostatic stress field of a dislocation that is surrounded by an impurity atmosphere was found and used to calculate the change in the effective radius of a dislocation line as a sink for interstitials and vacancies. The calculation of the impurity concentration in a Cottrell cloud takes into account the change in hydrostatic pressure produced by the presence of the cloud itself. It is found that void growth is eliminated whenever dislocations are surrounded by a condensed atmosphere of either oversized substitutional impurity atoms or interstitial impurity atoms. A condensed atmosphere will form whenever the average impurity concentration is larger than a critical concentration

  10. Simulation of thermally activated dislocation glide

    International Nuclear Information System (INIS)

    Roennpagel, D.; Mohles, V.

    1994-01-01

    Solid solution hardening was investigated by simulating the motion of a flexible dislocation in thermal equilibrium while overcoming obstacles by thermal activation. In a first approach, the waiting times before activation were analysed at several temperatures, external stresses and segment lengths. From statistical studies of such activation event, the effective attack frequency, Gibb's free enthalpy of activation and the activation volume were derived in strict analogy to the analysis of experimental data. As a second approach the average velocity of a dislocation gliding over an infinite row of equidistant obstacles was calculated by simulation. The temperature dependence of this speed significantly differs from that of the waiting times, indicating that kinetic effects must not be neglected even at high at high temperatures where dislocation motion is said to be 'overdamped'. (au)

  11. FEEDING ECOLOGY OF TREE-CLIMBING MANGROVE SESARMID CRABS FROM LUZON, PHILIPPINES

    Directory of Open Access Journals (Sweden)

    JIMMY TEVAR MASAGCA

    2009-01-01

    Full Text Available Despite the large ecological study of tree-climbing mangrove sesarmid crabs in other countries, the Philippine representatives appear to have not been investigated extensively. This paper presents the feeding ecology as to dependence on mangrove trees of sesarmids in different mangrove areas of southern Luzon. This is biased on the nature of the crab habitats, arboreal climbing skills and burrowing behavior of the sesarmids: Selatium elongatum and Episesarma versicolor − exclusive mangrove tree climbers (EMTC; Sarmatium germaini − occasional mangrove tree climber (OMTC; and the non-mangrove tree-climbing (NMTC sesarmids- Neosarmatium smithii, Perisesarma bidens and Perisesarma eumolpe

  12. Characteristics of the scientific researches in sport climbing (review of the articles, theses, programs, methodical works.

    Directory of Open Access Journals (Sweden)

    Sedliar Yu.V.

    2011-04-01

    Full Text Available The general estimation of the condition of the scientific developments will presented in sport climbing and on this base is specified the most perspective ways of scientific searching for in this area. Analysis publication reflecting different questions of preparation sport climbing athletes was organized. On base of the analysis of the special literature and coming from generally accepted in home science structure of the knowledge, was ascertained degree of the development different theoretical and practical aspect in this sphere. Discovered increase amount of the experimental studies in sport climbing.

  13. Positron trapping at dislocations in metals

    International Nuclear Information System (INIS)

    Bergersen, B.; McMullen, T.

    1977-01-01

    The trapping rate of positrons at dislocations in metals, and its temperature dependence, are calculated. Two different trapping processes, with the excess energy absorbed in either electron-hole pair formation or by phonon creation, are considered and the former is found to be the most important. An extension of the theory to include depletion of the positron density around the dislocations in a diffusion approximation is included. The trapping is found to be transition limited if the temperature is low or the trap potential shallow. At room temperature diffusion is important for deep traps. (author)

  14. Ipsilateral open anterior hip dislocation and open posterior elbow dislocation in an adult

    Directory of Open Access Journals (Sweden)

    Kumar Sunil

    2014-02-01

    Full Text Available 【Abstract】Open anterior dislocation of the hip is a very rare injury, especially in adults. It is a hyperabduction, external rotation and extension injury. Its combination with open posterior dislocation of the elbow has not been described in English language-based medical literature. Primary resuscitation, debridement, urgent reduction of dislocation, and adequate antibiotic support resulted in good clinical outcome in our patient. At 18 months follow-up, no signs of avascular necrosis of the femoral head or infection were observed.

  15. Features and functionality of speed and power capabilities of elite climbers and various types of rock climbing

    Directory of Open Access Journals (Sweden)

    O.A. Ryepko

    2013-12-01

    Full Text Available The purpose of this study was comparative and functional characterization of speed- force readiness elite athletes - representatives of climbing to the complexity, speed and climbers. The study involved 26 athletes: 10 masters of sports of international class (speed climbing, 10 masters of sports of international class (climbing difficulty, 6 world-class climbers. The age of the athletes was 19-22 years. Found that the different types of rock climbing have different requirements for the development of the components of speed- force readiness: speed climbing is more conducive to the development of explosive power and speed endurance, climbing on the complexity is more conducive to the development of power abilities and strength endurance in short time intervals. Taken in the study to compare climbing contributes to the development of strength endurance over longer intervals of time.

  16. 3D DD modelling of the prismatic loops and dislocations interaction in pure iron

    International Nuclear Information System (INIS)

    Novokshanov, R.; Roberts, S.

    2007-01-01

    Full text of publication follows: Neutron irradiation can increase the yield stress and reduce the ductility of metals. These effects are mainly caused by the interaction of dislocations with damage produced during irradiation. In iron irradiated with fast neutrons the damage takes the form of 1/2 and 1/2 prismatic dislocation loops (the size of the loops varies from 2 nm to 20 nm depending on the dose of irradiation). The interaction between such loops and dislocations is the subject of this research. 3D dislocation dynamics simulations have been carried out to model the interaction between prismatic loops and dis- locations in pure iron subject to uniaxial loading conditions. The primary goal was to understand the mechanism of interaction of a a/2 loop and a mobile dislocation. The simulations have shown a complicated 3D interaction resulting in either bowing around an obstacle (prismatic loop, Orowan mechanism) or cutting it through, carrying part of the loop away and leaving the other part behind. Cross-slip can be important, in a manner depending on the type of mobile dislocation, size, type and orientation of prismatic loop. The secondary goal was to investigate the dependence of the critical stress needed for dislocations to overcome the obstacles as a function of: size of loops, initial separation between loops, the direction of motion of the mobile dislocation and its type (pure edge or screw), and type of a loop (interstitial or vacancy). Many different configurations have been simulated. The size of the loops was varied from 10 nm to 100 nm; the separation between the loops in a row was varied from one to four loop diameters; the distance between the glide plane and the loop plane was varied from 0 to 20 nm. The glide plane of the mobile dislocation was either perpendicular to and or inclined to the loop plane. The results show a strong dependence of the critical stress on the size of the loops and the initial configuration. (authors)

  17. The fastest drop climbing on a wet conical fibre

    Science.gov (United States)

    Li, Er Qiang; Thoroddsen, Sigurdur T.

    2013-05-01

    We use high-speed video imaging to study the capillary-driven motion of a micro-droplet along the outside of a pre-wetted conical fiber. The cones are fabricated on a glass-puller with tip diameters as small as 1 μm, an order of magnitude smaller than in previous studies. The liquid is fed through the hollow fiber accumulating at the fiber tip to form droplets. The droplets are initially attached to the opening as they grow in size before detaching and traveling up the cone. This detachment can produce a transient oscillation of high frequency. The spatial variation of the capillary pressure drives the droplets towards the wider side of the cone. Various liquids were used to change the surface tension by a factor of 3.5 and viscosity by a factor of 1500. Within each droplet size and viscous-dissipation regime, the data for climbing speeds collapse on a single curve. Droplets traveling with and against gravity allow us to pinpoint the absolute strength of the driving capillary pressure and viscous stresses and thereby determine the prefactors in the dimensionless relationships. The motions are consistent with earlier results obtained from much larger cones. Translation velocities up to 270 mm/s were observed and overall the velocities follow capillary-viscous scaling, whereas the speed of the fastest droplets is limited by inertia following their emergence at the cone tip.

  18. The fastest drop climbing on a wet conical fibre

    KAUST Repository

    Li, Erqiang

    2013-05-21

    We use high-speed video imaging to study the capillary-driven motion of a micro-droplet along the outside of a pre-wetted conical fiber. The cones are fabricated on a glass-puller with tip diameters as small as 1 μm, an order of magnitude smaller than in previous studies. The liquid is fed through the hollow fiber accumulating at the fiber tip to form droplets. The droplets are initially attached to the opening as they grow in size before detaching and traveling up the cone. This detachment can produce a transient oscillation of high frequency. The spatial variation of the capillary pressure drives the droplets towards the wider side of the cone. Various liquids were used to change the surface tension by a factor of 3.5 and viscosity by a factor of 1500. Within each droplet size and viscous-dissipation regime, the data for climbing speeds collapse on a single curve. Droplets traveling with and against gravity allow us to pinpoint the absolute strength of the driving capillary pressure and viscous stresses and thereby determine the prefactors in the dimensionless relationships. The motions are consistent with earlier results obtained from much larger cones. Translation velocities up to 270 mm/s were observed and overall the velocities follow capillary-viscous scaling, whereas the speed of the fastest droplets is limited by inertia following their emergence at the cone tip.

  19. An ecological dynamics framework for the acquisition of perceptual-motor skills in climbing

    NARCIS (Netherlands)

    Seifert, Ludovic; Orth, Dominic; Button, Chris; Brymer, Eric; Davids, Keith

    2016-01-01

    Uncertainty in extreme sports performance environments, like rock and ice climbing, provides considerable psycho-emotional and physiological demands which challenge the acquisition of perceptual-motor skills. An ecological dynamics theoretical framework adopts concepts and tools of nonlinear

  20. strange beta: An assistance system for indoor rock climbing route setting

    Science.gov (United States)

    Phillips, C.; Becker, L.; Bradley, E.

    2012-03-01

    This paper applies the mathematics of chaos to the task of designing indoor rock-climbing routes. Chaotic variation has been used to great advantage on music and dance, but the challenges here are quite different, beginning with the representation. We present a formalized system for transcribing rock climbing problems and then describe a variation generator that is designed to support human route-setters in designing new and interesting climbing problems. This variation generator, termed strange beta, uses chaos to introduce novelty. We validated this approach with a large blinded study in a commercial climbing gym, in cooperation with experienced climbers and expert route setters. The results show that strange beta can help a human setter produce routes that are at least as good as, and in some cases better than, those produced in the traditional manner.

  1. Effect of sunflower climbing bean intercroping system on insect pest incidence and crop productivity

    International Nuclear Information System (INIS)

    Tuey, R.K.; Koros, I.; Wanyonyi, W.

    2001-01-01

    Intercropping of sunflower and climping beans were evaluated for pest incidence and yield advantages during the main season of 2000/2001 at KARI-NPBRC, Njoro. Three sunflower varieties, Fedha, Record, PAN-7553 and three climbing beans varieties, Puebla, Omukingi and Flora were laid out in a complete randomised block design with four replications. Sunflower was spaced at 75 x 30 cm while the climbing beans were spaced at 50 x 37.5 cm. Assessment of pest damage on various treatments commenced 17 days after planting. Results showed that low plant germination was mainly a result of dry weather and taht cutworm damage was insignificant. There was a sunflower x climbing bean variety interaction, which regulated the aphid infestation of the climbing beans. Sunflower variety PAN-7553 recorded significantly (P<0.01) more pecked heads than the other two varieties. (author)

  2. A three dimensional discrete dislocation dynamics modelling of the early cycles of fatigue in an austenitic stainless steel 316L: dislocation microstructure and damage analysis; Modelisation physique des stades precurseurs de l'endommagement en fatigue dans l'acier inoxydable austenitique 316L

    Energy Technology Data Exchange (ETDEWEB)

    Depres, Ch

    2005-07-01

    A numerical code modelling the collective behaviour of dislocations at a mesoscopic scale (Discrete Dislocation Dynamics code) is used to analyse the cyclic plasticity that occurs in surface grains of an AISI 316L stainless steel, in order to understand the plastic mechanism involved in crack initiation in fatigue. Firstly, the analyses of both the formation and the evolution of the dislocation microstructures show the crucial role of cross-slip played in the strain localization in the form of slip bands. As the cycling proceeds, the slip bands exhibit well-organized dislocation arrangements that substitute to dislocation tangles, involving specific interaction mechanisms between primary and deviate systems. Secondly, both the surface displacements generated by plastic slip and the distortion energy induced by the dislocation microstructure have been analysed. We find that an irreversible surface relief in the form of extrusion/intrusion can be induced by cyclic slip of dislocations. The number of cycles for the crack initiation follows a Manson-Coffin type law. The analyses of the concentration of the distortion energy and its repartition in the slip bands show that beneficial energetic zones may be present at the very beginning of the cycling, and that mode-II crack propagation in the surface grains results from a succession of micro-crack initiations along primary slip plane, which is facilitated by various effects (stress concentration due to surface relief, environment effects...). Finally, a dislocation-based model for cyclic plasticity is proposed from Discrete Dislocation Dynamics results. (author)

  3. Influence of dislocation glide on the spinodal decomposition of fatigued duplex stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Herenu, S., E-mail: herenu@ifir-conicet.gov.ar [Instituto de Fisica Rosario, Bv. 27 de Febrero 210 bis, (2000) Rosario, Santa Fe (Argentina); Sennour, M. [MINES ParisTech, Centre des Materiaux - UMR CNRS 7633 - 91003, Evry Cedex (France); Balbi, M.; Alvarez-Armas, I. [Instituto de Fisica Rosario, Bv. 27 de Febrero 210 bis, (2000) Rosario, Santa Fe (Argentina); Thorel, A. [MINES ParisTech, Centre des Materiaux - UMR CNRS 7633 - 91003, Evry Cedex (France); Armas, A.F. [Instituto de Fisica Rosario, Bv. 27 de Febrero 210 bis, (2000) Rosario, Santa Fe (Argentina)

    2011-09-25

    Highlights: {center_dot} Dislocations bands and microbands are developed in {alpha} phase of fatigued aged DSS. {center_dot} Inside these structures, demodulation of spinodal decomposition (SD) were found. {center_dot} This fact could take part in the cyclic softening displayed by DSS S32750. {center_dot} Cyclic tests at 475 deg. C show a saturation stage at the end of fatigue life. {center_dot} This could be explained by the effect of demodulation and creation of SD. - Abstract: The present work is focused on assessing the influence of dislocation movement on spinodal decomposition through scanning transmission electron microscopy (STEM) in combination with energy dispersive X-ray spectroscopy (EDS) analysis in aged duplex stainless steel (DSS) S32750. Dislocation bands and microbands are the prominent dislocation arrangements observed in fatigue tested aged samples. By EDS measurements it was found that the spinodal decomposition was dissolved inside these dislocations structures. Therefore, the mechanism of microband formation developed in the ferritic phase during cycling seems to be responsible for the demodulation of the spinodal decomposition and cyclic softening of the aged DSS.

  4. Evaluation of dislocation density in copper and brass α deformed by XRD peak width analysis

    International Nuclear Information System (INIS)

    Sousa, Talita Gama de

    2014-01-01

    The determination of dislocation density in metallic materials has been available for many years in scientific environment. This is due to the fact that the dislocations are the main responsible for plastic deformation, which, thereafter, markedly influences the mechanical properties. In this work, the dislocation density was analyzed through peak broadening of Xray diffraction (XRD) using Convolutional Multiple Whole Profile (CMWP) program. The measurements obtained by XRD were compared with those obtained from images observed by transmission electronic microscopy (TEM). The materials used in this study were pure copper and brass α as alloy 268 (6 % Cu and 34 % Zn), deformed by rolling and ECA (equal channel angular extrusion) processes. The results indicate that the XRD is a powerful tool for the characterization of the microstructure in relation to the dislocation density, as they were consistent to the TEM measurements, and also showed good relationship with measurements of hardness. Furthermore, through the dislocation density it was possible to verify the influence of stacking fault energy (SFE) in the evolution of the copper samples deformation process and its alloy, and that the presence of texture in rolled samples did not impair the measurements obtained by XRD technique. (author)

  5. Atomistic study of the hardening of ferritic iron by Ni-Cr decorated dislocation loops

    Science.gov (United States)

    Bonny, G.; Bakaev, A.; Terentyev, D.; Zhurkin, E.; Posselt, M.

    2018-01-01

    The exact nature of the radiation defects causing hardening in reactor structural steels consists of several components that are not yet clearly determined. While generally, the hardening is attributed to dislocation loops, voids and secondary phases (radiation-induced precipitates), recent advanced experimental and computational studies point to the importance of solute-rich clusters (SRCs). Depending on the exact composition of the steel, SRCs may contain Mn, Ni and Cu (e.g. in reactor pressure vessel steels) or Ni, Cr, Si, Mn (e.g. in high-chromium steels for generation IV and fusion applications). One of the hypotheses currently implied to explain their formation is the process of radiation-induced diffusion and segregation of these elements to small dislocation loops (heterogeneous nucleation), so that the distinction between SRCs and loops becomes somewhat blurred. In this work, we perform an atomistic study to investigate the enrichment of loops by Ni and Cr solutes and their interaction with an edge dislocation. The dislocation loops decorated with Ni and Cr solutes are obtained by Monte Carlo simulations, while the effect of solute segregation on the loop's strength and interaction mechanism is then addressed by large scale molecular dynamics simulations. The synergy of the Cr-Ni interaction and their competition to occupy positions in the dislocation loop core are specifically clarified.

  6. Non-basal dislocations should be accounted for in simulating ice mass flow

    Science.gov (United States)

    Chauve, T.; Montagnat, M.; Piazolo, S.; Journaux, B.; Wheeler, J.; Barou, F.; Mainprice, D.; Tommasi, A.

    2017-09-01

    Prediction of ice mass flow and associated dynamics is pivotal at a time of climate change. Ice flow is dominantly accommodated by the motion of crystal defects - the dislocations. In the specific case of ice, their observation is not always accessible by means of the classical tools such as X-ray diffraction or transmission electron microscopy (TEM). Part of the dislocation population, the geometrically necessary dislocations (GNDs) can nevertheless be constrained using crystal orientation measurements via electron backscattering diffraction (EBSD) associated with appropriate analyses based on the Nye (1950) approach. The present study uses the Weighted Burgers Vectors, a reduced formulation of the Nye theory that enables the characterization of GNDs. Applied to ice, this method documents, for the first time, the presence of dislocations with non-basal [ c ] or Burgers vectors. These [ c ] or dislocations represent up to 35% of the GNDs observed in laboratory-deformed ice samples. Our findings offer a more complex and comprehensive picture of the key plasticity processes responsible for polycrystalline ice creep and provide better constraints on the constitutive mechanical laws implemented in ice sheet flow models used to predict the response of Earth ice masses to climate change.

  7. Direct posterior reduction in a case of posttraumatic irreducible lateral atlantoaxial dislocation.

    Science.gov (United States)

    Salunke, Pravin; Sahoo, Sushanta K; Doddamani, Ramesh; Ahuja, Chirag K; Mukherjee, Kanchan K

    2014-06-01

    Posttraumatic true irreducible C1-2 lateral dislocation is rare. The mechanism of injury is likely to be different for this kind of dislocation. The management of such an injury and the technique for direct posterior reduction remain unclear because of its rarity. The authors describe the case of a 34-year-old man who sustained injury in a vehicular accident, leading to neck pain. Radiological studies revealed fixed right lateral and posterior C1-2 dislocation. Direct posterior open reduction was achieved by distracting the facets and rotating them in a counterclockwise direction. Care was taken to avoid direct or indirect injury to the vertebral arteries. Segmental C1-2 fusion was performed. Distraction with lateral extension injury possibly gives rise to this unique fracture dislocation. Preoperative imaging including angiography for vertebral arteries helps in defining the cause of fixity and in surgical planning. Direct posterior reduction is possible in such fixed C1-2 lateral dislocation, circumventing transoral surgery-provided the facets are preserved.

  8. Atomistic simulations of dislocation-precipitate interactions emphasize importance of cross-slip

    International Nuclear Information System (INIS)

    Singh, C.V.; Mateos, A.J.; Warner, D.H.

    2011-01-01

    This work examines the interaction of screw dislocations with Guinier-Preston (GP) zones using atomistic simulations. Both Orowan looping and cross-slip mechanisms are found to control the interactions. Cross-slip, occurring both at zero and finite temperatures, is found to either significantly reduce or enhance precipitate strengthening, depending upon the orientation of the dislocation-GP zone interaction. The orientation dependence, and its dependence on temperature, provides a micromechanical explanation for the experiments of Muraishi et al. (Philos. Mag. A 82 (2002) 2755).

  9. Continuum dislocation-density based models for the dynamic shock response of single-crystal and polycrystalline materials

    Science.gov (United States)

    Luscher, Darby

    2017-06-01

    The dynamic thermomechanical responses of polycrystalline materials under shock loading are often dominated by the interaction of defects and interfaces. For example, polymer-bonded explosives (PBX) can initiate under weak shock impacts whose energy, if distributed homogeneously throughout the material, translates to temperature increases that are insufficient to drive the rapid chemistry observed. In such cases, heterogeneous thermomechanical interactions at the mesoscale (i.e. between single-crystal and macroscale) lead to the formation of localized hot spots. Within metals, a prescribed deformation associated with a shock wave may be accommodated by crystallographic slip, provided a sufficient population of mobile dislocations is available. However, if the deformation rate is large enough, there may be an insufficient number of freely mobile dislocations. In these cases, additional dislocations may be nucleated, or alternate mechanisms (e.g. twinning, damage) activated in order to accommodate the deformation. Direct numerical simulation at the mesoscale offers insight into these physical processes that can be invaluable to the development of macroscale constitutive theories, if the mesoscale models adequately represent the anisotropic nonlinear thermomechanical response of individual crystals and their interfaces. This talk will briefly outline a continuum mesoscale modeling framework founded upon local and nonlocal variations of dislocation-density based crystal plasticity theory. The nonlocal theory couples continuum dislocation transport with the local theory. In the latter, dislocation transport is modeled by enforcing dislocation conservation at a slip-system level through the solution of advection-diffusion equations. The configuration of geometrically necessary dislocation density gives rise to a back-stress that inhibits or accentuates the flow of dislocations. Development of the local theory and application to modeling the explosive molecular crystal

  10. Electron-dislocation interaction at low temperatures. Progress report

    International Nuclear Information System (INIS)

    1978-01-01

    The interaction of mobile dislocations with electrons in copper and copper alloys has shown that dislocation motion in copper, at low temperature, can be treated as an analog of an underdamped oscillator. We have also shown that the viscous drag on mobile dislocations in type II superconductors can be treated as an acoustic attenuation of an elastic wave

  11. A case of posterior shoulder dislocation with ipsilateral humeral ...

    African Journals Online (AJOL)

    A case of posterior shoulder dislocation with ipsilateral humeral shaft fracture. P Sharma, S Meena, D Rastogi, B Chowdhury. Abstract. Posterior shoulder dislocations are rare and represent 2–5% of all traumatic shoulder dislocation. A combination of this injury with ipsilateral humeral shaft fracture is extremely rare event.

  12. Nanoscale dislocation shear loops at static equilibrium and finite temperature

    Science.gov (United States)

    Dang, Khanh; Capolungo, Laurent; Spearot, Douglas E.

    2017-12-01

    Atomistic simulations are used to determine the resolved shear stress necessary for equilibrium and the resulting geometry of nanoscale dislocation shear loops in Al. Dislocation loops with different sizes and shapes are created via superposition of elemental triangular dislocation displacement fields in the presence of an externally imposed shear stress. First, a bisection algorithm is developed to determine systematically the resolved shear stress necessary for equilibrium at 0 K. This approach allows for the identification of dislocation core structure and a correlation between dislocation loop size, shape and the computed shear stress for equilibrium. It is found, in agreement with predictions made by Scattergood and Bacon, that the equilibrium shape of a dislocation loop becomes more circular with increasing loop size. Second, the bisection algorithm is extended to study the influence of temperature on the resolved shear stress necessary for stability. An approach is presented to compute the effective lattice friction stress, including temperature dependence, for dislocation loops in Al. The temperature dependence of the effective lattice friction stress can be reliably computed for dislocation loops larger than 16.2 nm. However, for dislocation loops smaller than this threshold, the effective lattice friction stress shows a dislocation loop size dependence caused by significant overlap of the stress fields on the interior of the dislocation loops. Combined, static and finite temperature atomistic simulations provide essential data to parameterize discrete dislocation dynamics simulations.

  13. An irreducible ankle fracture dislocation: the Bosworth injury

    NARCIS (Netherlands)

    Schepers, Tim; Hagenaars, Tjebbe; den Hartog, Dennis

    2012-01-01

    Irreducible fracture dislocations of the ankle are rare and represent true orthopedic emergencies. We present a case of a fracture dislocation that was irreducible owing to a fixed dislocation of the proximal fibular fragment posterior to the lateral ridge of the tibia. This particular type of

  14. Monteggia fracture-dislocation: a case report, its' initial management ...

    African Journals Online (AJOL)

    This is a report and description of initial management of a fracture- dislocation, which was consequent to a sideswipe injury and consisted of a combination of the following injuries; lateral dislocation of the radial head, fractures of the olecranon and proximal ulna in the left forearm. The radial head dislocation and fracture of ...

  15. An Irreducible Ankle Fracture Dislocation: The Bosworth Injury

    NARCIS (Netherlands)

    T. Schepers (Tim); T. Hagenaars (Tjebbe); D. den Hartog (Dennis)

    2012-01-01

    textabstractIrreducible fracture dislocations of the ankle are rare and represent true orthopedic emergencies. We present a case of a fracture dislocation that was irreducible owing to a fixed dislocation of the proximal fibular fragment posterior to the lateral ridge of the tibia. This particular

  16. Lack of experience is a significant factor in the missed diagnosis of perilunate fracture dislocation or isolated dislocation

    Directory of Open Access Journals (Sweden)

    Ilker Çolak

    2018-01-01

    Conclusion: The results of this study indicated that lack of experience was the most important factor in the misdiagnosis of perilunate fracture dislocation or isolated dislocation. Level of Evidence: Level IV, diagnostic study.

  17. Effect of pretreatments and processing conditions on anti-nutritional factors in climbing bean flours

    Directory of Open Access Journals (Sweden)

    Emmanuel Mugabo

    2017-04-01

    Full Text Available It is difficult for many Rwandans to utilize climbing bean seeds (Phaseolus vulgaris. L mainly because of longer cooking time (2 hours and the high consumption of basic fuel. Climbing beans also contain anti-nutritional factors such tannins, phytates, trypsin inhibitors and phytohemagglutinins that limit nutrient absorption. One way to solve this problem is to utilize the flour of climbing beans made from different treatments and processing methods. In this study, climbing beans were pre-treated by soaking them in water for 24 hours, soaking in 2% sodium bicarbonate solution and steam blanching for 10 minutes. After that, pre-treated climbing beans were processed into flours by processing methods such as roasting, cooking and germination where anti-nutritional factors were reduced. The pretreatments did not significantly (p>0.05 affect phytates in climbing bean flours but processing conditions significantly (p<0.05 reduced it. Pretreatments and processing conditions significantly (p<0.05 reduced tannin content. The pretreatments followed by different processing conditions significantly (p<0.05 decreased trypsin inhibitors content. The great significant decrease in phytohemagglutinins content was observed in pretreatment followed by different processing methods. All pretreatments and processing conditions effectively decreased anti-nutritional factors at low level. However, pretreatments or untreated followed by germination and roasting were found to be the most and the least effective respectively.  Making flour from germinated climbing bean seeds is a good option for sustainable food processing as it reduces anti-nutritional factors. It is an inexpensive method in terms of time, energy and fuel for Rwandan households, restaurants and industries where climbing bean seeds are integral part of daily meal.

  18. A Control Method Based on Modal Transformation for Biped Robots to Climb Unknown Steps

    Science.gov (United States)

    Shimmyo, Shuhei; Nakazato, Miki; Mikami, Kei; Sato, Tomoya; Sakaino, Sho; Ohnishi, Kouhei

    This paper proposes a control method based on modal transformation for biped robots to climb unknown steps. This method is able to control the foot position of the biped robot and the ground reaction force acting in vertical direction when the biped robot climbs unknown steps in a double-support phase. The effectiveness of the proposed method is confirmed by simulation and experimental results.

  19. Dislocation structures, effective and internal stresses of cyclic stained ferritic stainless steel

    Czech Academy of Sciences Publication Activity Database

    Petrenec, Martin; Polák, Jaroslav

    2001-01-01

    Roč. 72, č. 279 (2001), s. 129-133 ISSN 1429-6055. [Medzynarodowe Sympozjum - Metody oceny struktury oraz wlasnosci materialów i wyrobów /16./. Komorní Lhotka, 11.12.2001-13.12.2001] Institutional research plan: CEZ:AV0Z2041904 Keywords : dislocation * cyclicling * stresses Subject RIV: JL - Materials Fatigue, Friction Mechanics

  20. Inflicted T12 fracture-dislocation: CT/MRI correlation and mechanistic implications

    Energy Technology Data Exchange (ETDEWEB)

    Tran, Brandon [Brigham and Women' s Hospital, Section of Neuroradiology, Department of Radiology, Boston, MA (United States); Silvera, Michelle [Children' s Hospital Boston, Division of Neuroradiology, Department of Radiology, Boston, MA (United States); Newton, Alice [Children' s Hospital Boston, Division of General Pediatrics, Boston, MA (United States); Kleinman, Paul K. [Children' s Hospital Boston, Department of Radiology, Boston, MA (United States)

    2007-11-15

    We describe the CT and MRI findings of a thoracolumbar neurocentral synchondrosis fracture-dislocation in an abused infant. The morphologic features of this classically described fracture, and the associated cervical and sacral spine injuries displayed on cross-sectional imaging, provide compelling evidence for a mechanism of massive hyperflexion and axial spinal loading. (orig.)

  1. Screening for congenital dislocation of the hip

    International Nuclear Information System (INIS)

    Fendel, H.

    1987-01-01

    Although the prevalence of (idiopathic) congenital dislocation of the hip (CDH) within the Member States of the European Community is not exactly known, it must be considered as a major problem of public health care and protection. By assessment of available data one can assume that between 1 and 2% of all newborns have dislocation or instability of one or both hips. There is a female predominance of 4:1 and some risk factors are known. The reasons of a higher prevalence in some areas are not yet well understood. Most of instable hips will spontaneously become stable within the first days or weeks of life. However, a considerable number of infants (less than 1%) will remain with instable hips which may dislocate. Dislocation either present at birth or as a result of persistent instability leads to subsequent hip deformation. This is a serious event for each affected individual, and is a heavy load on health care and social costs for the public. Treatment of CDH is easy and usually effective when started early, i.e. before the fourth month of life. The earlier treatment is started the easier, shorter, safer and less expensive it is and its impairment on child development and mother-child interaction can be held to a minimum. Screening for CDH is therefore the most important part of health protection in early infancy. However, this paper concludes that neither sonography nor X-ray examinations are appropriate for CDH screening

  2. managing temporomandibular joint dislocation in ibadan

    African Journals Online (AJOL)

    manoeuvre and IMF. Fifty percent of the chronic cases were successfully managed with the Hippocrates manoeuvre. Follow up was < 2 weeks in 7 of the cases. ... in the above named hospital was anterior dislocation, the female gender predominance, ... also presented very early probably due to an awareness of where to ...

  3. stabilisation of posterior sternoclavicular joint dislocation using

    African Journals Online (AJOL)

    A case is reported where palmaris longus tendon was used to stabilise the joint following open reduction. INTRODUCTION. Posterior Sternoclavicular joint dislocation is a relatively rare injury and is reported to have been first documented by Sir Astley Cooper in 1824 (1, 2). It is a potentially life threatening injury due to the ...

  4. Tendoscopic treatment of recurrent peroneal tendon dislocation

    NARCIS (Netherlands)

    Scholten, Peter E.; Breugem, Stefan J. M.; van Dijk, C. Niek

    2013-01-01

    To study the possibility of tendoscopic treatment of recurrent peroneal tendon dislocation. The case of one patient is described including the tendoscopic technique to deepen the fibular groove. In this single case, there were no complications, recovery time was short, and there was no recurrence of

  5. An isolated cuboid dislocation. A case report

    Directory of Open Access Journals (Sweden)

    K. Sheahan

    2017-01-01

    Conclusion: Our take home message from this case report is that cuboid dislocations are rare injuries and are important to be aware of in reviewing X-rays in the E.D. Particularly in patients with inversion and plantar flexion type injuries to their foot and ankle joint, with an inability to weight bear and lateral midfoot pain following their injury.

  6. Ab initio phonon scattering by dislocations

    Science.gov (United States)

    Wang, Tao; Carrete, Jesús; van Roekeghem, Ambroise; Mingo, Natalio; Madsen, Georg K. H.

    2017-06-01

    Heat management in thermoelectric and power devices as well as in random access memories poses a grand challenge and can make the difference between a working and an abandoned device design. Despite the prevalence of dislocations in all these technologies, the modeling of their thermal resistance is based on 50-year-old analytical approximations, whose simplicity was driven by practical limitations rather than physical insight. We introduce an efficient ab initio approach based on Green's functions computed by two-dimensional reciprocal space integration. By combining elasticity theory and density functional theory, we calculate the scattering strength of a 90∘ misfit edge dislocation in Si. Because of the breakdown of the Born approximation, earlier literature models fail, even qualitatively. We find that a dislocation density larger than 109cm-2 is necessary to substantially influence thermal conductivity at room temperature and above. We quantify how much of the reduction of thermal conductivity measured in nanograined samples can be explained by realistic dislocation concentrations.

  7. Missed isolated volar dislocation of the scaphoid

    DEFF Research Database (Denmark)

    Kolby, Lise; Larsen, Søren; Jørring, Stig

    2007-01-01

    A patient presented with volar dislocation of the scaphoid, the diagnosis of which had been missed for two weeks. He was treated with open reduction through a combined volar and dorsal approach with decompression of the median nerve, internal fixation, and a cast for eight weeks. One year postope...... postoperatively the functional result was good. A radiograph showed no sign of avascular necrosis....

  8. Left Dislocation: a typological overview | Westbury | Stellenbosch ...

    African Journals Online (AJOL)

    The Left Dislocation construction is a typologically universal phenomenon that has received detailed analysis, from both formal and functional perspectives, in a number of genetically and areally diverse languages. The present paper aims to provide a general overview of this cross-linguistic research with a concentration ...

  9. Completion of a Dislocated Metric Space

    Directory of Open Access Journals (Sweden)

    P. Sumati Kumari

    2015-01-01

    Full Text Available We provide a construction for the completion of a dislocated metric space (abbreviated d-metric space; we also prove that the completion of the metric associated with a d-metric coincides with the metric associated with the completion of the d-metric.

  10. Dislocation Microstructures in Fatiqued Copper Polycrystals

    DEFF Research Database (Denmark)

    Winter, A.T.; Pedersen, Ole Bøcker; Rasmussen, K.V.

    1981-01-01

    Dislocation structures characteristic of persistent slip bands were observed in the interior of polycrystalline copper after fatigue. At low strain amplitudes, within the plateau on the cyclic stress-strain curve, only structures identical to those seen in single crystals were observed. This allows...

  11. Tailoring surgical management of dislocated clavicle fractures

    NARCIS (Netherlands)

    Wijdicks, F.J.G.

    2013-01-01

    In this thesis literature research and clinical studies are presented to assist physicians in the decision making process for surgical treatment of dislocated midshaft clavicle fractures (DMCF). In Chapter 1 an introduction is given regarding the background, aim and outline of this thesis. Chapter 2

  12. Computed tomography of traumatic atlantooccipital dislocation.

    Science.gov (United States)

    Gerlock, A J; Mirfakhraee, M; Benzel, E C

    1983-09-01

    Although atlantooccipital dislocation is a well-recognized radiological entity, its computed tomographic (CT) recognition has not been previously described. It is the purpose of this report to show the complementary role of CT in precisely defining the abnormalities in both the coronal and the sagittal reconstruction planes. A case is presented and the literature is reviewed.

  13. Cruciate paralysis secondary to traumatic atlantooccipital dislocation.

    Science.gov (United States)

    Sweet, Jennifer; Ammerman, Joshua; Deshmukh, Vivek; White, Joseph

    2010-01-01

    Cruciate paralysis is a clinical phenomenon thought to result from injury to decussating pyramidal tract fibers at the cervicomedullary junction, producing clinical findings of upper-extremity weakness out of proportion to the lower extremities. The authors present, to their knowledge, the first reported case of cruciate paralysis resulting from atlantooccipital dislocation.

  14. Subacute dislocation of the elbow following Galeazzi fracture-dislocation of the radius: A case report.

    Science.gov (United States)

    Rajeev, Aysha; Senevirathna, Shanaka; Harrison, John

    2011-12-20

    The Galeazzi fracture-dislocation was originally described by Sir Astley Cooper in 1822 but was named after Italian surgeon Ricardo Galeazzi in 1934. It is an injury classified as a radial shaft fracture with associated dislocation of the distal radioulnar joint and disruption of the forearm axis joint. The associated distal radioulnar joint injury may be purely ligamentous in nature, tearing the triangular fibrocartilaginous complex, or involve bony tissue (that is, ulnar styloid avulsions) or both. We report this case because of the rare association of posterior dislocation of the elbow along with Galeazzi fracture-dislocation. To the best of our knowledge, this has not been previously reported in the English literature. A 26-year-old Caucasian man presented to our department after a fall from a motorbike. He sustained a closed, isolated Galeazzi fracture-dislocation of the right forearm and no associated elbow injuries, and this necessitated open reduction and internal fixation of the radius. Post-operative radiographs films were satisfactory. However, clinical and radiological evidence of ipsilateral elbow dislocation was noted at a five-week follow-up, subsequently requiring open reduction of the joint and collateral ligament repair. Our patient was noted to have full elbow and forearm function at three months. Although the Galeazzi fracture-dislocation has been classically described as involving only the distal radioulnar joint, traumatic forces can be transmitted to the elbow via the interosseous membrane of the forearm. This can lead to instability of the elbow joint. Therefore, we recommend that, in every case of forearm fracture, both elbow and wrist joints be assessed clinically as well as radiologically for subluxation or dislocation.

  15. Beneficial aerodynamic effect of wing scales on the climbing flight of butterflies.

    Science.gov (United States)

    Slegers, Nathan; Heilman, Michael; Cranford, Jacob; Lang, Amy; Yoder, John; Habegger, Maria Laura

    2017-01-30

    It is hypothesized that butterfly wing scale geometry and surface patterning may function to improve aerodynamic efficiency. In order to investigate this hypothesis, a method to measure butterfly flapping kinematics optically over long uninhibited flapping sequences was developed. Statistical results for the climbing flight flapping kinematics of 11 butterflies, based on a total of 236 individual flights, both with and without their wing scales, are presented. Results show, that for each of the 11 butterflies, the mean climbing efficiency decreased after scales were removed. Data was reduced to a single set of differences of climbing efficiency using are paired t-test. Results show a mean decrease in climbing efficiency of 32.2% occurred with a 95% confidence interval of 45.6%-18.8%. Similar analysis showed that the flapping amplitude decreased by 7% while the flapping frequency did not show a significant difference. Results provide strong evidence that butterfly wing scale geometry and surface patterning improve butterfly climbing efficiency. The authors hypothesize that the wing scale's effect in measured climbing efficiency may be due to an improved aerodynamic efficiency of the butterfly and could similarly be used on flapping wing micro air vehicles to potentially achieve similar gains in efficiency.

  16. Hydrogen accumulation around dislocation loops and edge dislocations: from atomistic to mesoscopic scales in BCC tungsten

    Science.gov (United States)

    De Backer, A.; Mason, D. R.; Domain, C.; Nguyen-Manh, D.; Marinica, M.-C.; Ventelon, L.; Becquart, C. S.; Dudarev, S. L.

    2017-12-01

    In a fusion tokamak, the plasma interacts with the metallic wall and the divertor. Hydrogen isotopes penetrate and diffuse into the material and interact with defects where they are trapped. Neutrons produced by the fusion reactions in the plasma are stopped in the material, creating defects, including vacancy and interstitial clusters, and dislocation loops. The trapping of hydrogen in vacancies has been extensively investigated. In our recent paper (De Backer et al 2017 Nucl. Fusion), we proposed a multi-scale model for H trapping and accumulation around interstitial defects, dislocation loops and dislocation lines. These defects create a long-range elastic field that attracts and may retain H atoms. A two-shell model with a short-range core region and a long-range elastic shell has been parameterized using a database of density functional theory (DFT) calculations. This model gives the number of H atoms forming the Cottrell atmosphere of a defect at finite temperature. In this paper, we present new DFT calculations of large dislocation loops decorated with up to 80 H, and explore our two-shell model in fusion relevant conditions. We conclude that large dislocation loops and edge dislocations can trap a significant number of hydrogen atoms in the core at temperatures up to 800 K, and also in the elastic field if the background hydrogen concentration is high.

  17. Climbing exercise enhances osteoblast differentiation and inhibits adipogenic differentiation with high expression of PTH/PTHrP receptor in bone marrow cells.

    Science.gov (United States)

    Menuki, Kunitaka; Mori, Toshiharu; Sakai, Akinori; Sakuma, Miyuki; Okimoto, Nobukazu; Shimizu, Yuki; Kunugita, Naoki; Nakamura, Toshitaka

    2008-09-01

    We developed previously a mouse voluntary climbing exercise model as a physiological mechanical loading model and reported that climbing exercise increased bone formation, but its effect on adipogenesis is unknown. We assessed the effects of loading and PTH/PTHrP receptor (PTHR1) on bone marrow adipocyte differentiation in relation with osteoblast differentiation. 8-week-old C57BL/6J male mice were divided into ground control (GC) and climbing exercise (EX) group. Mice were housed in 100-cm towers and climbed up toward a bottle placed at the top of the cage to drink water. The values of bone volume and osteoblast number were significantly higher while those of marrow adipocyte volume and number were significantly lower in the 28dayEX group than 28dayGC group. The mRNA expression levels of adipocyte differentiation genes CCAAT/enhancer-binding proteins (C/EBP) beta and delta were lower in 4dayEX mice, while the adipocyte specific genes fatty acid binding protein (aP2) and phosphoenolpyruvate carboxykinase (PEPCK) expressions were lower in 7dayEX mice. In primary bone marrow cell cultures, the number of alkaline phosphatase-positive colony forming units-fibroblastic (ALP+ CFU-f) and Oil-red-O-positive cells were both increased in the 4dayEX group. Climbing exercise transiently increases both osteogenic and adipogenic potential in bone marrow stromal cells, and inhibits terminal adipocyte differentiation and promotes osteoblast differentiation. Immunoreactivity for the PTHR1 was intense on osteoblastic cell lineage in the endosteal tibial metaphysis. PTHR1 mRNA expression was increased in 4dayEX mice and PTHR1-positive cells were increased after 7 days in the experimental group. Ex vivo addition of PTHR1 antibody decreased and that of PTHrP(1-34) increased the number of ALP+ CFU-f in bone marrow cell cultures obtained at 4 days after the exercise, while the addition of PTHR1 antibody increased and PTHrP(1-34) decreased the number of Oil-red-O-positive cells. Our

  18. Dislocation/separation injuries among US high school athletes in 9 selected sports: 2005-2009.

    Science.gov (United States)

    Kerr, Zachary Y; Collins, Christy L; Pommering, Thomas L; Fields, Sarah K; Comstock, R Dawn

    2011-03-01

    To investigate the epidemiology of dislocations/separations in a nationally representative sample of high school student-athletes participating in 9 sports. Descriptive epidemiologic study. Sports injury data for the 2005-2009 academic years were collected using an Internet-based injury surveillance system, Reporting Information Online (RIO). A nationally representative sample of 100 US high schools. Injuries sustained as a function of sport and gender. Dislocation/separation rates, body site, outcome, surgery, and mechanism. Dislocations/separations represented 3.6% (n = 755) of all injuries. The most commonly injured body sites were the shoulder (54.9%), wrist/hand (16.5%), and knee (16.0%); 18.4% of dislocations/separations were recurrences of previous injuries at the same body site; 32.3% of injuries were severe (ie, student-athletes unable to return to play within 3 weeks of the injury date), and 11.8% required surgical repair. The most common mechanisms of injury were contact with another player (52.4%) and contact with the playing surface (26.4%). Injury rates varied by sport. In gender-comparable sports, few variations in patterns of injury existed. Rates were highest in football (2.10 per 10 000 athletic exposures) and wrestling (1.99) and lowest in baseball (0.24) and girls' soccer (0.27). Although dislocation/separation injuries represent a relatively small proportion of all injuries sustained by high school student-athletes, the severity of these injuries indicates a need for enhanced injury prevention efforts. Developing effective targeted preventive measures depends on increasing our knowledge of dislocation/separation rates, patterns, and risk factors among high school athletes.

  19. Work softening in nanocrystalline materials induced by dislocation annihilation

    DEFF Research Database (Denmark)

    Ungar, Tamas; Li, Li; Tichy, Geza

    2011-01-01

    Cold rolling reduces the quantity of dislocation densities in Ni–18% Fe alloys prepared by electrochemical deposition. The dislocation density evolution proposed earlier for the linearly decreasing work-hardening rate during stage III is revisited. The solution of the differential equation predicts...... that when the initial dislocation density is smaller or larger than the saturation value, then the dislocation density will increase or decrease during further plastic deformation. The predictions are verified by experimental values of dislocation densities determined by X-ray line-profile analysis....

  20. [Complex fracture-dislocation of the proximal interphalangeal joint. A case report and focus on palmar proximal interphalangeal fractures-dislocations].

    Science.gov (United States)

    Lawson, E; Thomsen, L; Hans-Moevi Akué, A; Falcone, M-O

    2013-10-01

    The palmar fracture-dislocation of the proximal interphalangeal (PIP) joint of fingers is an uncommon injury. We report a complex form in a 16-year old teenager, associating a palmar fracture-dislocation and a fracture of the base of the middle phalanx with the dorsal fragment dislocated between the neck of the proximal phalange and the palmar plate. The management was surgical with open reduction and fixation of the fragments by K-wires and temporary PIP arthrorisis. The result at 6months of follow- up after removal of the wires and physiotherapy was satisfactory. The patient was painless with a range of motion of 115°. Clinically, the sagittal and frontal stability of the joint both in flexion and extension was maintained. Osseous healing was obtained on X-ray control. The patient went back to his usual activities. A focus on palmar fracture-dislocations of PIP joint is presented through incidence, mechanism and treatment. Copyright © 2013 Elsevier Masson SAS. All rights reserved.

  1. STATISTICAL MECHANICS MODELING OF MESOSCALE DEFORMATION IN METALS

    Energy Technology Data Exchange (ETDEWEB)

    Anter El-Azab

    2013-04-08

    The research under this project focused on a theoretical and computational modeling of dislocation dynamics of mesoscale deformation of metal single crystals. Specifically, the work aimed to implement a continuum statistical theory of dislocations to understand strain hardening and cell structure formation under monotonic loading. These aspects of crystal deformation are manifestations of the evolution of the underlying dislocation system under mechanical loading. The project had three research tasks: 1) Investigating the statistical characteristics of dislocation systems in deformed crystals. 2) Formulating kinetic equations of dislocations and coupling these kinetics equations and crystal mechanics. 3) Computational solution of coupled crystal mechanics and dislocation kinetics. Comparison of dislocation dynamics predictions with experimental results in the area of statistical properties of dislocations and their field was also a part of the proposed effort. In the first research task, the dislocation dynamics simulation method was used to investigate the spatial, orientation, velocity, and temporal statistics of dynamical dislocation systems, and on the use of the results from this investigation to complete the kinetic description of dislocations. The second task focused on completing the formulation of a kinetic theory of dislocations that respects the discrete nature of crystallographic slip and the physics of dislocation motion and dislocation interaction in the crystal. Part of this effort also targeted the theoretical basis for establishing the connection between discrete and continuum representation of dislocations and the analysis of discrete dislocation simulation results within the continuum framework. This part of the research enables the enrichment of the kinetic description with information representing the discrete dislocation systems behavior. The third task focused on the development of physics-inspired numerical methods of solution of the coupled

  2. New theory for Mode I crack-tip dislocation emission

    Science.gov (United States)

    Andric, Predrag; Curtin, W. A.

    2017-09-01

    A material is intrinsically ductile under Mode I loading when the critical stress intensity KIe for dislocation emission is lower than the critical stress intensity KIc for cleavage. KIe is usually evaluated using the approximate Rice theory, which predicts a dependence on the elastic constants and the unstable stacking fault energy γusf for slip along the plane of dislocation emission. Here, atomistic simulations across a wide range of fcc metals show that KIe is systematically larger (10-30%) than predicted. However, the critical (crack tip) shear displacement is up to 40% smaller than predicted. The discrepancy arises because Mode I emission is accompanied by the formation of a surface step that is not considered in the Rice theory. A new theory for Mode I emission is presented based on the ideas that (i) the stress resisting step formation at the crack tip creates "lattice trapping" against dislocation emission such that (ii) emission is due to a mechanical instability at the crack tip. The new theory is formulated using a Peierls-type model, naturally includes the energy to form the step, and reduces to the Rice theory (no trapping) when the step energy is small. The new theory predicts a higher KIe at a smaller critical shear displacement, rationalizing deviations of simulations from the Rice theory. Specific predictions of KIe for the simulated materials, usually requiring use of the measured critical crack tip shear displacement due to complex material non-linearity, show very good agreement with simulations. An analytic model involving only γusf, the surface energy γs, and anisotropic elastic constants is shown to be quite accurate, serves as a replacement for the analytical Rice theory, and is used to understand differences between Rice theory and simulation in recent literature. The new theory highlights the role of surface steps created by dislocation emission in Mode I, which has implications not only for intrinsic ductility but also for crack tip

  3. Long-term depression of climbing fiber-evoked calcium transients in Purkinje cell dendrites

    Science.gov (United States)

    Weber, John T.; De Zeeuw, Chris I.; Linden, David J.; Hansel, Christian

    2003-01-01

    In recent years much has been learned about the molecular requirements for inducing long-term synaptic depression (LTD) in various brain regions. However, very little is known about the consequences of LTD induction for subsequent signaling events in postsynaptic neurons. We have addressed this issue by examining homosynaptic LTD at the cerebellar climbing fiber (CF)–Purkinje cell (PC) synapse. This synapse is built for reliable and massive excitation: Activation of a single axon produces an unusually large α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor-mediated synaptic current, the depolarization of which drives a regenerative complex spike producing a large, widespread Ca2+ transient in PC dendrites. Here we test whether CF LTD has an impact on dendritic, complex spike-evoked Ca2+ signals by simultaneously performing long-term recordings of complex spikes and microfluorimetric Ca2+ measurements in PC dendrites in rat cerebellar slices. Our data show that LTD of the CF excitatory postsynaptic current produces a reduction in both slow components of the complex spike waveform and complex spike-evoked dendritic Ca2+ transients. This LTD of dendritic Ca2+ signals may provide a neuroprotective mechanism and/or constitute “heterosynaptic metaplasticity” by reducing the probability for subsequent induction of those forms of use-dependent plasticity, which require CF-evoked Ca2+ signals such as parallel fiber–PC LTD and interneuron–PC LTP. PMID:12601151

  4. Recombination properties of dislocations in GaN

    Science.gov (United States)

    Yakimov, Eugene B.; Polyakov, Alexander Y.; Lee, In-Hwan; Pearton, Stephen J.

    2018-04-01

    The recombination activity of threading dislocations in n-GaN with different dislocation densities and different doping levels was studied using electron beam induced current (EBIC). The recombination velocity on a dislocation, also known as the dislocation recombination strength, was calculated. The results suggest that dislocations in n-GaN giving contrast in EBIC are charged and surrounded by a space charge region, as evidenced by the observed dependence of dislocation recombination strength on dopant concentration. For moderate (below ˜108 cm-2) dislocation densities, these defects do not primarily determine the average diffusion length of nonequilibrium charge carriers, although locally, dislocations are efficient recombination sites. In general, it is observed that the effect of the growth method [standard metalorganic chemical vapor deposition (MOCVD), epitaxial lateral overgrowth versions of MOCVD, and hydride vapor phase epitaxy] on the recombination activity of dislocations is not very pronounced, although the average diffusion lengths can widely differ for various samples. The glide of basal plane dislocations at room temperature promoted by low energy electron irradiation does not significantly change the recombination properties of dislocations.

  5. Ultrasound as a probe of dislocation density in aluminum

    International Nuclear Information System (INIS)

    Mujica, Nicolás; Cerda, Maria Teresa; Espinoza, Rodrigo; Lisoni, Judit; Lund, Fernando

    2012-01-01

    Graphical abstract: Display Omitted - Abstract: Dislocations are at the heart of the plastic behavior of crystalline materials yet it is notoriously difficult to perform quantitative, non-intrusive measurements of their single or collective properties. Dislocation density is a critical variable that determines dislocation mobility, strength and ductility. On the one hand, individual dislocations can be probed in detail with transmission electron microscopy. On the other hand, their collective properties must be simulated numerically. Here we show that ultrasound technology can be used to measure dislocation density. This development rests on theory—a generalization of the Granato–Lücke theory for the interaction of elastic waves with dislocations—and resonant ultrasound spectroscopy (RUS) measurements. The chosen material is aluminum, to which different dislocation contents were induced through annealing and cold-rolling processes. The dislocation densities obtained with RUS compare favorably with those inferred from X-ray diffraction, using the modified Williamson–Hall method.

  6. BILATERAL PATHOLOGICAL HIP DISLOCATION IN CHILDREN

    Directory of Open Access Journals (Sweden)

    Yuriy E. Garkavenko

    2017-03-01

    Full Text Available Introduction. Pathological dislocation of the hip is one of the most severe complications of acute hematogenous osteomyelitis. The program of treatment for children with pathological hip dislocation is complex, but it has been sufficiently developed and implemented very successfully. At the same time, the available literature provides no cases of treating children with bilateral pathological hip dislocations after hematogenous osteomyelitis. There is no information on the incidence of such cases or in regards to remote functional results. Materials and methods. The results of the treatment of 18 children with bilateral pathological dislocation of the hip after hematogenous osteomyelitis are presented, which constituted 23.1% of the total number of patients (78 who underwent surgery in 2000–2016 for the diagnosis of pathological hip dislocation. Both hip joints were surgically operated on in 12 patients, while one hip joint was operated on in 6 patients. To assess the anatomical and functional state of hip joints, the clinical and roentgenological diagnostic techniques were used. Results and discussion. To stabilize and restore the function of the hip joints, 18 children underwent 30 surgical interventions: simple open hip reduction (19 and open hip reduction with hip arthroplasty with one (6 or two (5 demineralized osteochondral allogeneic grafts. The decision regarding the possibility of performing surgical intervention on the second hip joint was made only after a child's check-up examination was complete and after positive information about the anatomical and functional state of the operated hip joint was obtained. According to these criteria, 14 (77.8% children underwent surgical treatment of the second hip joint 1–1.5 years after the course of conservative measures to restore the range of motion in the previously operated hip joint. Over a period of 1–12 years, 17 patients were examined, 10 of which underwent an operation on both

  7. Determining dislocation densities from the extinction effect (review)

    International Nuclear Information System (INIS)

    Ivanov, A.N.; Polyakov, A.M.; Skakov, Yu.A.

    1987-01-01

    Much attention is being given to dynamic x-ray scattering in crystals containing defects. As general diffraction theory for crystals with defects does not at present extend beyond formal expressions and there is no rigorous theory of diffraction by crystals containing dislocations, one describes extinction in a nonideal crystal via phenomenological theories. In this paper, the authors review the various methods of analyzing the dislocation structure from the integral intensities which are based on three extinction models: Darwin's extinction theory; mosaic-crystal scattering theory; and the transport equations method proposed by Stephan for Bragg geometry and Laue geometry. The most rigorous method in a theoretical respect of those covered in this review is based on Kato's extinction theory. The authors consider it necessary to devise a general theory of x-ray scattering for crystals with any type of long-range order in the displacement pattern, although this paper has dealt with some of the applications of quantum mechanics and statistical physics in describing diffraction

  8. Dislocations and elementary processes of plasticity in FCC metals: atomic scale simulations; Dislocations et processus elementaires de la plasticite dans les metaux CFC: apports des simulations a l'echelle atomique

    Energy Technology Data Exchange (ETDEWEB)

    Rodney, D

    2000-07-01

    We present atomic-scale simulations of two elementary processes of FCC crystal plasticity. The first study consists in the simulation by molecular dynamics, in a nickel crystal, of the interactions between an edge dislocation and glissile interstitial loops of the type that form under irradiation in displacement cascades. The simulations show various atomic-scale interaction processes leading to the absorption and drag of the loops by the dislocation. These reactions certainly contribute to the formation of the 'clear bands' observed in deformed irradiated materials. The simulations also allow to study quantitatively the role of the glissile loops in irradiation hardening. In particular, dislocation unpinning stresses for certain pinning mechanisms are evaluated from the simulations. The second study consists first in the generalization in three dimensions of the quasi-continuum method (QCM), a multi-scale simulation method which couples atomistic techniques and the finite element method. In the QCM, regions close to dislocation cores are simulated at the atomic-scale while the rest of the crystal is simulated with a lower resolution by means of a discretization of the displacement fields using the finite element method. The QCM is then tested on the simulation of the formation and breaking of dislocation junctions in an aluminum crystal. Comparison of the simulations with an elastic model of dislocation junctions shows that the structure and strength of the junctions are dominated by elastic line tension effects, as is assumed in classical theories. (author)

  9. Transtriquetral perihamate fracture-dislocation: case report

    Directory of Open Access Journals (Sweden)

    Frederico Barra de Moraes

    2016-08-01

    Full Text Available ABSTRACT The wrist is a region that is very vulnerable to injuries of the extremities. Among these injuries, fractures of the pyramidal bone (or triquetrum in association with dislocation of the hamate and carpal instability are uncommon. They are generally correlated with high-energy trauma and may be associated with neurovascular deficits, muscle-tendon disorders, skin lesions or injuries to other carpal bones. Thus, in this report, one of these rare cases of transtriquetral perihamate fracture-dislocation with carpal instability is presented, diagnosed by means of radiography on the right wrist of the patient who presented pain, edema and limitation of flexion-extension of the carpus after trauma to the region. The stages of attending to the case are described, from the initial consultation to the surgical treatment and physiotherapy, which culminated in restoration of the strength and range of motion of the wrist.

  10. Performance, Mood, and Anxiety During a Climb of Mount Everest.

    Science.gov (United States)

    Karinen, Heikki M; Tuomisto, Martti T

    2017-12-01

    Karinen, Heikki M., and Martti T. Tuomisto. Performance, mood, and anxiety during a climb of Mount Everest. High Alt Med Biol. 18:400-410, 2017. Various studies have shown the deleterious effects of high-altitude hypoxia on visual, motor, somatosensory, cognitive, and emotional function and also in intelligence tests, reaction time, speech comprehension, hand steadiness, visual contrast discrimination, and word association tests. Because optimal cognitive abilities may be crucial for mountain climbers' safety, this study was intended to evaluate the changes in cognitive performance, mood, and anxiety during an Everest expedition lasting almost 3 months. A set of physiological (Lake Louise score, oxygen saturation), cognitive (Colorado perceptual speed [CPS] test, number comparison [NC] test), and emotional measurements (Profile of Mood States, anxiety responses, psychological inflexibility) were collected from nine climbers on a partly unsupported Mount Everest expedition at various time points during the course of the expedition at Everest Base Camp (EBC). For confidence intervals we used 95% simultaneous Bonferroni corrected interval (BCI) for the differences. During this expedition, the estimates of trait anxiety decreased 13% toward the end of expedition after successful summiting (p = 0.004). Simultaneously, fatigue appeared to diminish and the CPS speed results improved 13%. Most expedition members suffered mild symptoms of acute mountain sickness during the first days in the EBC, but this did not affect the speed or the number of mistakes made in the CPS or NC tests. In CPS test the differences between pretest and the physically most demanding period (EBC4, BCI: 0.01, 4.43) and between EBC1 and EBC4 (BCI: 0.57, 4.99), between EBC2 and EBC4 (BCI: 0.45, 4.88), and between EBC3 and EBC4 (BCI: 1.12, 5.55) were significant, showing ever improving results during the expedition. The most important finding in this study was that well-motivated and trained, self

  11. Lifting as We Climb: Recognizing Intersectional Gender Violence in Law

    Directory of Open Access Journals (Sweden)

    Shreya Atrey

    2015-12-01

    Full Text Available This paper interrogates the meaning of lifting all women as we climb the ladder of gender equality and justice by recognizing that gender violence affects women differently. This is because violence against women is perpetrated not only on the basis of their gender or sex but also other identities of race, religion, caste, region, age, disability, nationality, sexual orientation etc. With reference to CEDAW jurisprudence and examples from India, I seek to explain this understanding with the help of a normative framework of ‘intersectional integrity’. The framework insists on considering claimants as a whole by tracing unique and shared patterns of gender violence when it is also based on other identities such as race, religion, caste, region, age, disability, nationality, and sexual orientation. I argue that applying the framework allows us to diagnose and address the nature of violence suffered on multiple identities, in a clear and comprehensive way. Este artículo cuestiona el sentido de levantar a todas las mujeres a medida que se asciende la escalera de la igualdad de género y la justicia, reconociendo que la violencia de género afecta a las mujeres de manera diferente. Esto se debe a que la violencia contra las mujeres se comete no sólo sobre la base de su género o sexo, sino también por su raza, religión, casta, región, edad, discapacidad, nacionalidad, orientación sexual, etc. Se pretende explicar esta afirmación con la ayuda de un marco normativo de “integridad interseccional”, a través de referencias a la jurisprudencia del CEDAW y ejemplos de la India. El marco insiste en considerar a las demandantes en su conjunto, trazando patrones únicos y compartidos de violencia de género cuando se basa también en otras identidades como raza, religión, casta, región, edad, discapacidad, nacionalidad, orientación sexual. Se sostiene que la aplicación del marco permite diagnosticar y abordar la naturaleza de la violencia

  12. Traumatic atlantooccipital dislocation injury in children.

    Science.gov (United States)

    Nichols, J; West, J S

    1994-10-01

    The tragedy of trauma turns into triumph when the surgery team members' efforts result in victory for the patient. Nowhere is this more true than in successful pediatric trauma care. Giving a child a second chance at life and the family an opportunity for a new beginning is the highest reward for the trauma team's years of professional training and practice. Traumatic atlantoocipital dislocation injury usually results in death, but recent neurosurgery trauma advances are increasing pediatric survival rates.

  13. The Relevant Role of Dislocations in the Martensitic Transformations in Cu-Al-Ni Single Crystals

    Science.gov (United States)

    Gastien, R.; Sade, M.; Lovey, F. C.

    2018-02-01

    The interaction between dislocations and martensitic transformations in Cu-Al-Ni alloys is shortly reviewed. Results from many researchers are critically analyzed towards a clear interpretation of the relevant role played by dislocations on the properties of shape memory alloys in Cu-based alloys. Both thermally and stress-induced transformations are considered and focus is paid on two types of transitions, the β→β' and the formation of a mixture of martensites: β→β' + γ'. After cycling in the range where both martensites are formed, the twinned γ' phase is inhibited and cycling evolves into the formation of only β'. A model which considers the difference in energy of each γ' twin variant due to the introduced dislocations quantitatively explains the inhibition of γ' in both thermally and stress-induced cycling. The type of dislocations which are mainly introduced, mixed with Burgers vector belonging to the basal plane of the β' martensite, enables also to explain the unmodified mechanical behavior during β→β' cycling. The reported behavior shows interesting advantages of Cu-Al-Ni single crystals if mechanical properties are comparatively considered with those in other Cu-based alloys.

  14. Congenital hip dislocation: Radiological screening or diagnosis?

    International Nuclear Information System (INIS)

    Kalifa, G.; Faure, C.

    1987-01-01

    Congenital hip dislocation is a perfect example of public health problems: its incidence is high 0.6, to 2% of newborns in France and an early detection allows an easy and successful treatment. The current situation in our country is not satisfactory for several reasons: - Too many children are treated without reasons because of misleading radiological pictures; - Conversely, some dislocations are discovered only at the walking age, the treatment becoming then more difficult and less effective; - Almost 300,000 radiological examinations of the hip for screening are performed each year and among them 100,000 in newborns. This is not satisfactory as it is commonly admitted now that radiological examination at birth is unreliable and frequently misleading. For all these reasons a special working group has been settled up by the General Direction of Health, including physicians of different practices, from different specialities. The conclusion of this group will be published in a special booklet and can be summarized as follows: The group recommends to perform detection of congenital hip dislocation mainly by the clinical examination. This examination may be difficult but it must be performed very early, the first day of life, repeated several times, at the end of the first week and during the first, second, and third month. Every baby in this country must undergo several clinical examinations up to one year of age

  15. Open Galeazzi fracture with ipsilateral elbow dislocation.

    Science.gov (United States)

    Adanır, Oktay; Yüksel, Serdar; Beytemur, Ozan; Güleç, M Akif

    2016-08-01

    Combination of the Galeazzi fracture and dislocation of the elbow joint in same extremity is very rare. In this article, we report a 26-year-old male patient with a posterolateral dislocation of the elbow and ipsilateral volar type Galeazzi fracture. We performed closed reduction for the elbow dislocation during admission to the emergency department. Patient was taken to the operating room in the sixth hour of his application to emergency department and open wound on the ulnovolar region of the wrist was closed primarily after irrigation and debridement. We performed open reduction and internal fixation of the radial fracture with a dynamic compression plate. After fixation, we evaluated the stability of the elbow joint and distal radioulnar joint. Distal radioulnar joint was unstable under fluoroscopic examination and fixed with one 1.8 mm Kirschner wire in a pronated position. Then, elbow joint was stable. One year after surgery, patient had no pain or sings of instability. At the last follow-up, range of motion of the elbow was 10°-135° and forearm pronation and supination were 70°.

  16. Thoracic fractures and dislocations in motorcyclists

    International Nuclear Information System (INIS)

    Daffner, R.H.; Deeb, Z.L.; Rothfus, W.E.

    1987-01-01

    Motorcyclists who are involved in accidents generally suffer severe multiple injuries, some of which are not readily apparent on initial examination. One such subtle injury is fracture, with or without dislocation, in the upper thoracic spine. The severe spinal cord damage produced by the injury is often overshadowed by cerebral or cervical injury. Proper diagnosis is further hampered by the fact that the upper thoracic region is difficult to examine radiographically on plain films, particularly when using portable equipment. Of a group of 14 motorcyclists having 26 fractures and/or dislocations in the thoracic region, 12 had 24 injuries between T3 and T8. These 24 injuries represented 56% of the fractures and/or dislocations encountered in a larger study of trauma to the thoracic vertebral column. All of these were flexion injuries, suffered when the individual was thrown from the motorcycle and struck a large, solid object. In three cases, the diagnosis was delayed as much as 48 h because proper films were not obtained initially. Because of the serious consequences of delayed treatment, we recommended that all motorcyclists who have sustained severe trauma be examined by overpenetrated film of the upper thoracic region. (orig.)

  17. The surface energy, thermal vibrations of dislocation lines and the critical crack extension force

    International Nuclear Information System (INIS)

    Chiang, Chien.

    1979-09-01

    The connections between atomic structure and mechanical properties of metals are interested by many physicist and mechanists recently. The authors of this paper try to connect the fracture of materials with the surface energy and dislocation properties, which may be treated with lattice dynamics and electron theory of solids. It shows that to combine the knowledge of solid state physics and fracture mechanics is quite important. (author)

  18. The effect of clustering on the mobility of dislocations during aging in Nb-microalloyed strip cast steels: In situ heating TEM observations

    International Nuclear Information System (INIS)

    Shrestha, Sachin L.; Xie, Kelvin Y.; Ringer, Simon P.; Carpenter, Kristin R.; Smith, David R.; Killmore, Chris R.; Cairney, Julie M.

    2013-01-01

    Cluster-strengthened Nb-microalloyed strip cast steels are of interest as clustering during aging leads to an enhancement in strength without compromising ductility, resulting in desirable mechanical properties. However, the precise strengthening mechanism is not well understood. Using in situ heating transmission electron microscopy, clustering was found to impede the movement of dislocations during aging. The attractive combination of ductility and strength was attributed to the effects of recovery and the restricted movement of dislocations through clustering

  19. Analysis of sociodemographic, sport and psychological profile in a rock-climbing experience on university students

    Directory of Open Access Journals (Sweden)

    Pablo Morilla Portela

    2013-07-01

    Full Text Available The relationships among several psychological factors in rock climbing was proved a long time ago, nevertheless, most researches are limited to very artificial situations, far away from nature. There are few studies which have carried out this kind of investigation in the natural environment and have combined data collection with real rock climbing practice. The instruments used for this data collection were two questionnaires: CSAI-2 and another one specifically designed to gather the necessary information about sociodemographic characteristic and sport habits. In our work we have studied various individuals’ features (sociodemographic, general sport and outdoor profiles and we have confirmed how they are interrelated and their influence on several psychological factors (cognitive anxiety, somatic anxiety and self-confidence. Through this article we show that there are higher percentages of women than men participants who climb IV-V grade, whereas in higher grades the percentages equalize. Regarding psychological factors, we can notice how on the one hand those participants who climb higher grades and are more interested in rock climbing, feel lower cognitive anxiety and somatic anxiety, while on the other hand they feel higher self-confidence levels

  20. An atomic string model for a screw dislocation in iron: Implications for the development of interatomic potentials

    International Nuclear Information System (INIS)

    Gilbert, M.R.; Dudarev, S.L.; Chiesa, S.; Derlet, P.M.

    2009-01-01

    Thermally activated motion of screw dislocations is the rate-determining mechanism for plastic deformation and fracture of body centred cubic (bcc) metals and alloys. Recent experimental observations by S.G. Roberts' group at Oxford showed that ductile-brittle behaviour of bcc vanadium, tungsten, pure iron, and iron-chromium alloys is controlled by an Arrhenius process in which the energy for thermal activation is proportional to the formation energy for a double kink on a b= 1/2 screw dislocation, where b is the Burgers vector of the dislocation. Interpreting these experimental observations and extending the analysis to the case of irradiated materials requires developing a full quantitative treatment for perfect and kinked screw dislocations. Modelling screw dislocations also presents a challenge for the development of interatomic potentials. Recent density functional theory (DFT) calculations have revealed that the ground-state structure of the core of screw dislocations in all the bcc transition metals is non-degenerate and symmetric, whereas inter-atomic potentials used in molecular dynamics simulations for these metals often predict a degenerate, symmetry-broken core-structure. In this work we show how, by treating the structure of a screw dislocation within a multistring Frenkel-Kontorova model, we can develop a criterion that guarantees the correct symmetric core of the dislocation. Extending this treatment, we find a systematic recipe for constructing Finnis-Sinclair-type potentials that are able, as a matter of routine, produce non-degenerate core structures of 1/2 screw dislocations. Modelling thermally activated mobility of screw dislocations also requires that the transition pathway between stable core positions of a dislocation is accurately reproduced. DFT data indicates that the shape of the 'Peierls energy barrier' is a single-hump curve, including transitional configurations close to the so-called 'hard' structure. Interatomic potentials have, up

  1. Interaction processes between vacancies and dislocations in molybdenum in the temperature range around 0.3 of the melting temperature

    Energy Technology Data Exchange (ETDEWEB)

    Zelada-Lambri, G.I. [Facultad de Ciencias Exactas, Ingenieria y Agrimensura, Universidad Nacional de Rosario, Laboratorio de Materiales, Escuela de Ingenieria Electrica, Avenida Pellegrini 250, 2000 Rosario (Argentina); Lambri, O.A. [Facultad de Ciencias Exactas, Ingenieria y Agrimensura, Universidad Nacional de Rosario, Laboratorio de Materiales, Escuela de Ingenieria Electrica, Avenida Pellegrini 250, 2000 Rosario (Argentina); Instituto de Fisica Rosario, Member of the CONICET' s Research Staff (Argentina)], E-mail: olambri@fceia.unr.edu.ar; Bozzano, P.B. [Laboratorio de Microscopia Electronica, Unidad de Actividad Materiales, Centro Atomico Constituyentes, Comision Nacional de Energia Atomica, Avenida General Paz 1499, 1650 San Martin (Argentina); Garcia, J.A. [Departamento de Fisica Aplicada II, Facultad de Ciencias y Tecnologia, Universidad del Pais Vasco, Apartado 644, 48080 Bilbao, Pais Vasco (Spain); Celauro, C.A. [Reactor Nuclear RA-4, Facultad de Ciencias Exactas, Ingenieria y Agrimensura, Universidad Nacional de Rosario, Riobamba y Berruti, 2000 Rosario (Argentina)

    2008-10-15

    Mechanical spectroscopy, electrical resistivity and transmission electron microscopy studies have been performed on pre-strained neutron irradiated single crystalline molybdenum in order to check the interaction processes between vacancies and dislocations in the temperature range between room temperature and 1273 K. The anelastic relaxation in molybdenum which appears between 800 K and 1273 K has been separated in two different physical mechanisms depending on the temperature of appearance of the relaxation peak. The physical mechanism which controls the damping peak appearing at around 800 K was related with the dragging of jogs by the dislocation under movement assisted by vacancy diffusion. The damping peak which appears at higher temperatures of about 1000 K was more consistent with the formation and diffusion of vacancies assisted by the dislocation movement.

  2. A Low-Cost, Light-Weight Climbing Robot for Inspection of Class Curtains

    Directory of Open Access Journals (Sweden)

    Ran Liang

    2014-07-01

    Full Text Available This paper presents design of a climbing robot for inspection of glass curtain walls. The double-chamber structure enables the robot to climb over grooves on the glasses. In order to reduce the weight, both number and shape of the chambers are specially considered, and the pressure structure is optimized by FEA method. The statics models of different adsorption situations are also analyzed and deduced for the operational safety. In addition, design of the working arm and the wireless control system are introduced in detail. Finally, experiments of the robot are illustrated, including adsorption on different surfaces, vertical and horizontal groove-crossing as well as glass inspection. These experiments fully prove the theoretical analysis and demonstrate the climbing performance of the robot.

  3. Polymorphism of dislocation core structures at the atomic scale.

    Science.gov (United States)

    Wang, Zhongchang; Saito, Mitsuhiro; McKenna, Keith P; Ikuhara, Yuichi

    2014-01-01

    Dislocation defects together with their associated strain fields and segregated impurities are of considerable significance in many areas of materials science. However, their atomic-scale structures have remained extremely challenging to resolve, limiting our understanding of these ubiquitous defects. Here, by developing a complex modelling approach in combination with bicrystal experiments and systematic atomic-resolution imaging, we are now able to pinpoint individual dislocation cores at the atomic scale, leading to the discovery that even simple magnesium oxide can exhibit polymorphism of core structures for a given dislocation species. These polymorphic cores are associated with local variations in strain fields, segregation of defects, and electronic states, adding a new dimension to understanding the properties of dislocations in real materials. The findings advance our fundamental understanding of basic behaviours of dislocations and demonstrate that quantitative prediction and characterization of dislocations in real materials is possible.

  4. Simulation of structure and annihilation of screw dislocation dipoles

    DEFF Research Database (Denmark)

    Rasmussen, Torben; Vegge, Tejs; Leffers, Torben

    2000-01-01

    Large scale atomistic simulations are used to investigate the properties of screw dislocation dipoles in copper. Spontaneous annihilation is observed for dipole heights less than 1 nm. Equilibrated dipoles of heights larger than 1 nm adopt a skew configuration due to the elastic anisotropy of Cu....... The equilibrium splitting width of the screw dislocations decreases with decreasing dipole height, as expected from elasticity theory. The energy barriers, and corresponding transition states for annihilation of stable dipoles are determined for straight and for flexible dislocations for dipole heights up to 5.......2 nm. In both cases the annihilation is initiated by cross-slip of one of the dislocations. For straight dislocations the activation energy shows a linear dependence on the inverse dipole height, and for flexible dislocations the dependence is roughly linear for the dipoles investigated....

  5. Climbing for preventing and treating health problems: a systematic review of randomized controlled trials

    Directory of Open Access Journals (Sweden)

    Fechtelpeter, Dennis

    2011-01-01

    Full Text Available Objective: To summarize the best available evidence on effectiveness of therapeutic or sport climbing in preventing or treating health problems. Methods: We searched Medline, Embase, CENTRAL, PsycINFO, PEDro, OTseeker and SportDiscus for randomized controlled trials published up to December 26, 2010. We included all trials assessing patient-relevant outcomes. Two reviewers independently selected relevant studies, assessed their methodological quality and extracted data. Quality of evidence was rated using the GRADE system. Data were entered into RevMan 5 to calculate effect sizes and 95% confidence intervals where appropriate.Results: Eligible for inclusion were four RCTs studying the effectiveness of climbing in (a geriatric patients, (b adults with multiple sclerosis, (c adults with chronic low-back pain and (d children with disabilities and poor motor function. The sample sizes ranged between 20 and 95. All trials had major methodological limitations. We found very low quality evidence that therapeutic climbing may improve activities of daily living in geriatric patients compared to physiotherapy as measured by the Barthel index (difference in mean change score: 2.32 [95%-CI: 0.45 to 4.19]. We found very low quality evidence that therapeutic climbing compared to standard exercise therapy may improve physical functioning (difference in mean change score: 16.15 [95%-CI: 4.45 to 27.85] and general physical health (13.14 [95%-CI: 3.61 to 22.67] as measured by the SF-36 in adults with chronic low back-pain. Conclusions: Evidence for the effectiveness of therapeutic climbing is limited to small trials at high risk of bias. The effects of therapeutic climbing are therefore unclear.

  6. Using a body sensor network to measure the effect of fatigue on stair climbing performance

    International Nuclear Information System (INIS)

    Bergmann, Jeroen H M; Smith, Ian C H; Mayagoitia, Ruth E

    2012-01-01

    In terms of self-rated health, the most important activities of daily living are those involving mobility. Of these activities stair climbing is regarded as the most strenuous. A loss of stair climbing ability with age is normally associated with a loss of muscle strength and power, while other factors that influence muscle function, such as fatigue, are often not taken into account. So far no research has been published on how long-lasting fatigue affects activities of daily living, despite the fact that it has been repeatedly proven, in laboratory settings, to influence muscle force production over long periods of time. Technological advances in body sensor networks (BSNs) now provide a method to measure performance during complex real-life situations. In this study the use of a BSN was explored to investigate the effects of long-lasting fatigue on stair climbing performance in 20 healthy adults. Stair climbing performance was measured before and after a fatiguing protocol using a BSN. Performance was defined by temporal and spatial parameters. Long-lasting fatigue was successfully induced in all participants using an exercise protocol. The BSN showed that post-exercise fatigue did not influence stair climbing times (p > 0.2) and no meaningful changes in joint angles were found. No effect on overall stair climbing performance was found, despite a clear presence of long-lasting fatigue. This study shows that physiological paradigms can be further explored using BSNs. Ecological validity of lab-based measurements can be increased by combining them with BSNs. (paper)

  7. Closed Reduction of ?Irreducible? Posterolateral Knee Dislocation - A Case Report

    OpenAIRE

    Tateda, Satoshi; Takahashi, Atsushi; Aizawa, Toshimi; Umehara, Jutaro

    2016-01-01

    Introduction: Posterolateral rotary knee dislocation is a rare orthopedic injury that is considered to be irreducible by closed reduction because of soft tissue incarceration. Here, we present a case of posterolateral rotary knee dislocation, which was reduced by closed manipulation. Case report: The patientwas a 33-year-old man who sustained a twisting injury to his right knee that was diagnosed as posterolateral rotary knee dislocation by plain radiographs and the characteristic physical fi...

  8. Static Dislocation Interactions in Thin Channels between Cuboidal Particles

    Czech Academy of Sciences Publication Activity Database

    Dlouhý, Antonín; Probst-Hein, M.; Eggeler, G.

    309-310, - (2001), s. 278-282 ISSN 0921-5093. [Dislocations 2000. Gaithersburg, 19.06.2000-22.06.2000] R&D Projects: GA MŠk OC P3.50 Institutional research plan: CEZ:AV0Z2041904 Keywords : discrete dislocation modeling * single crystal superalloys * .gamma./.gamma.'-interface dislocations Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.978, year: 2001

  9. Orthodontic Mini-implants for Treatment of Long-term Anterior Dislocation of Temporomandibular Joint

    Directory of Open Access Journals (Sweden)

    Amit Dahiya

    2014-01-01

    Full Text Available Acute dislocation of the temporomandibular joint (TMJ is a relatively common occurrence; chronic long-term dislocation is rare. Variance in the duration of dislocation and anatomical considerations make the treatment for long-standing dislocation complex and controversial. This case report describes a new method of conservative management of a long-standing TMJ dislocation using orthodontic mini-implants.

  10. A multistage controlled intervention to increase stair climbing at work: effectiveness and process evaluation.

    Science.gov (United States)

    Bellicha, Alice; Kieusseian, Aurélie; Fontvieille, Anne-Marie; Tataranni, Antonio; Copin, Nane; Charreire, Hélène; Oppert, Jean-Michel

    2016-04-11

    Stair climbing helps to accumulate short bouts of physical activity throughout the day as a strategy for attaining recommended physical activity levels. There exists a need for effective long-term stair-climbing interventions that can be transferred to various worksite settings. The aims of this study were: 1) to evaluate short- and long-term effectiveness of a worksite stair-climbing intervention using an objective measurement of stair climbing and a controlled design; and 2) to perform a process evaluation of the intervention. We performed a controlled before-and-after study. The study was conducted in two corporate buildings of the same company located in Paris (France), between September, 2013 and September, 2014. The status of either "intervention site" or "control site" was assigned by the investigators. Participants were on-site employees (intervention site: n = 783; control site: n = 545 at baseline). Two one-month intervention phases using signs (intervention phase 1) and enhancement of stairwell aesthetics (intervention phase 2) were performed. The main outcome was the change in stair climbing, measured with automatic counters and expressed in absolute counts/day/100 employees and percent change compared to baseline. Qualitative outcomes were used to describe the intervention process. Stair climbing significantly increased at the intervention site (+18.7%) but decreased at the control site (-13.3%) during the second intervention phase (difference between sites: +4.6 counts/day/100 employees, p < 0.001). After the intervention and over the long term, stair climbing returned to baseline levels at the intervention site, but a significant difference between sites was found (intervention site vs. control site: +2.9 counts/day/100 employees, p < 0.05). Some important facets of the intervention were implemented as intended but other aspects had to be adapted. The main difficulty reported by the company's staff members lay in matching the internal

  11. Biologically-inspired synthetic dry adhesives for wall-climbing robots

    Science.gov (United States)

    Murphy, Michael P.

    Animals such as insects, spiders, and lizards are capable of clinging to and climbing on a variety of surfaces, from rough stone to smooth silicon. Hairy microscale arrays of structures on their feet conform to surface roughness to create millions of points of contact, creating a large overall contact area. Weak intermolecular forces (van der Waals forces) between each fiber tip and the surface sum to large overall forces due to the high number of contacts. In this work we present the fabrication, characterization, and demonstration of synthetic polyurethane fibrillar adhesives inspired by these animals. Angled polymer micro-fiber arrays are fabricated and characterized. A tip modification technique is presented which enables fabrication of fibers with flat mushroom shaped tips which greatly increase the adhesion of the fibers, up to 5N/cm 2 (normal direction), and with a magnitude within the range of geckos (10 N/cm2) in the shear direction on smooth surfaces. We present a fabrication technique to create fibers with angled flat mushroom-shaped tips which replicate the directional characteristics of geckos, gripping in one direction (within the range of gecko adhesion) and releasing easily in the other. Multilevel hierarchical structures with specialized tips for roughness adaptation are also presented. Fiber hierarchies from the millimeter scale to the sub-micron scale are demonstrated, including three-level fiber fabrication with specialized tips. Hierarchical structures demonstrate up to 5 times the adhesion of an unstructured sample, and requiring up to 10 times the detachment energy. Finally, an agile, wireless, palm-sized wall climbing robot which uses the synthetic fibrillar dry adhesives to climb is presented. Waalbot , named after the van der Waals forces it uses to climb, exploits the attachment and detachment characteristics of the developed dry adhesives, capabilities include climbing smooth surfaces such as glass in any orientation on any surface slope

  12. On the origin of dislocation loops in irradiated materials: A point of view from silicon

    Energy Technology Data Exchange (ETDEWEB)

    Claverie, Alain, E-mail: claverie@cemes.fr; Cherkashin, Nikolay

    2016-05-01

    Numerous dislocation loops are often observed in irradiated and nuclear materials, affecting many physical properties. The understanding of their origin and of their growth mechanism remains unclear rendering all modeling efforts elusive. In this paper, we remind the knowledge which has been gained during the last 20 years on the formation and growth of extrinsic dislocations loops in irradiated/implanted silicon. From the compilation of a large number of experimental results, a unified picture describing the thermal evolution of interstitial defects, from the di-interstitial stable at room temperature, to “magic-size” clusters then to rod-like defects and finally to large dislocation loops of two types has emerged. All these defects grow by Ostwald ripening, i.e. by interchanging the interstitial atoms they are composed of, and transform from one to the other driven by the resulting reduction of the defect formation energy. A model has been proposed and is now integrated into process simulators which quantitatively describes the thermal evolution of all these defects, based on pertinent formation energies. The influence of the proximity of free surfaces or other recombining interfaces can be integrated, allowing simulating the possible dissolution of defects. It is suggested that, beyond silicon, the same type of scenario may take place in many materials. Dislocation loops are just one, easily detectable among many, type of defects which forms during the growth of self-interstitials. They do not nucleate but result from the growth and transformation of smaller defects.

  13. A numerical spectral approach to solve the dislocation density transport equation

    International Nuclear Information System (INIS)

    Djaka, K S; Taupin, V; Berbenni, S; Fressengeas, C

    2015-01-01

    A numerical spectral approach is developed to solve in a fast, stable and accurate fashion, the quasi-linear hyperbolic transport equation governing the spatio-temporal evolution of the dislocation density tensor in the mechanics of dislocation fields. The approach relies on using the Fast Fourier Transform algorithm. Low-pass spectral filters are employed to control both the high frequency Gibbs oscillations inherent to the Fourier method and the fast-growing numerical instabilities resulting from the hyperbolic nature of the transport equation. The numerical scheme is validated by comparison with an exact solution in the 1D case corresponding to dislocation dipole annihilation. The expansion and annihilation of dislocation loops in 2D and 3D settings are also produced and compared with finite element approximations. The spectral solutions are shown to be stable, more accurate for low Courant numbers and much less computation time-consuming than the finite element technique based on an explicit Galerkin-least squares scheme. (paper)

  14. Elbow fracture-dislocation combined with Galeazzi fracture in adult: A case report and literature review.

    Science.gov (United States)

    Asadollahi, Saeed; Shepherd, David; Hau, Raphael C

    2013-01-01

    Galeazzi fracture associated with ipsilateral posterior elbow dislocation and radial head fracture is a rare pattern of injury. Few reports exist that describes this injury pattern and its treatment. We describe a case report of simultaneous occurrence of Galeazzi fracture and ipsilateral dislocation of elbow. A 58 year-old female presented with Galeazzi fracture and posterior elbow dislocation associated with radial head fracture of left upper extremity. This was managed with closed reduction of the elbow, open reduction and internal fixation of the radial shaft fracture and K-wire stabilisation of the unstable distal radioulnar joint. Prophylactic fasciotomy was performed. At 10 months follow-up, the outcome was favourable with the American shoulder and elbow surgeon score of 92 and the disabilities of the arm, shoulder and hand score of 18. The presumed mechanism of the injury was a forceful axial loading of a hyperpronated forearm and extended elbow. Our literature review shows that this pattern of injury occurs as a result of high energy trauma in young individuals, and successful outcome can be achieved by addressing each component of this complex injury individually. Simultaneous occurrence of elbow dislocation and Galeazzi fracture seems to be the result of extreme axial force and unique position of upper extremity at the time of impact. Individualised approach to each component of this injury can result in favourable outcome. Crown Copyright © 2013. Published by Elsevier Ltd. All rights reserved.

  15. Atomistic simulations of the formation of -component dislocation loops in α-zirconium

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Cong, E-mail: dai.cong@queensu.ca; Balogh, Levente; Yao, Zhongwen; Daymond, Mark R., E-mail: mark.daymond@queensu.ca

    2016-09-15

    The formation of -component dislocation loops in α-Zr is believed to be responsible for the breakaway irradiation growth experimentally observed under high irradiation fluences. However, while -loop growth is well described by existing models, the atomic mechanisms responsible for the nucleation of -component dislocation loops are still not clear. In the present work, both interstitial and vacancy -type dislocation loops are initially equilibrated at different temperatures. Cascades simulations in the vicinity of the -type loops are then performed by selecting an atom as the primary knock-on atoms (PKAs) with different kinetic energies, using molecular dynamics simulations. No -component dislocation loop was formed in cascades simulations with a 10 keV PKA, but -component interstitial loops were observed after the interaction between discontinuous 50 keV PKAs and pre-existing -type interstitial loops. The comparisons of cascades simulations in volumes having pre-existing -type interstitial and vacancy loops suggest that the reaction between the PKAs and -type interstitial loops is responsible for the formation of -component interstitial loops.

  16. Tensile testing study of dynamic interactions between dislocations and precipitate in vanadium alloys

    International Nuclear Information System (INIS)

    Tougou, Kouichi; Nogiwa, Kimihiro; Tachikawa, Kazuhiro; Fukumoto, Ken-ichi

    2013-01-01

    To investigate the hardening of fine Ti(OCN) precipitate, we performed in situ transmission electron microscopy (TEM) observations during tensile testing of dislocations gliding through fine Ti(OCN) precipitates in thermally aged V–4Cr–4Ti alloys. The obstacle strength parameter was estimated from the critical bow-out angle, ϕ, of the dislocation lines from the microstructural change during tensile deformation observed in the TEM images. From image processing analysis of the dislocation motion, the value of the obstacle strength parameter of Ti(OCN) precipitates of 4-nm size was determined to be 0.30. The increase in yield stress calculated from the measured dislocation behavior pinned around precipitates was Δσ in situ = 43 MPa, and the increase in yield stress measured by the micro-Vickers hardness test was Δσ HV = 49.5 MPa. Data from in situ TEM observations during tensile testing and from micro-Vickers hardness tests were in good agreement; thus, the obstacle strength parameter of the Ti(OCN) precipitates of 4-nm size was successfully obtained experimentally. The obstacle strength parameter also was compared with data from a previous study, and there was also quite good agreement. Therefore, the obstacle strength parameter obtained from this study is measurable and is a reliable measure of mechanical property changes following precipitation in V–4Cr–4Ti alloys

  17. Rocket launcher: A novel reduction technique for posterior hip dislocations and review of current literature.

    Science.gov (United States)

    Dan, Michael; Phillips, Alfred; Simonian, Marcus; Flannagan, Scott

    2015-06-01

    We provide a review of literature on reduction techniques for posterior hip dislocations and present our experience with a novel technique for the reduction of acute posterior hip dislocations in the ED, 'the rocket launcher' technique. We present our results with six patients with prosthetic posterior hip dislocation treated in our rural ED. We recorded patient demographics. The technique involves placing the patient's knee over the shoulder, and holding the lower leg like a 'Rocket Launcher' allow the physician's shoulder to work as a fulcrum, in an ergonomically friendly manner for the reducer. We used Fisher's t-test for cohort analysis between reduction techniques. Of our patients, the mean age was 74 years (range 66 to 85 years). We had a 83% success rate. The one patient who the 'rocket launcher' failed in, was a hemi-arthroplasty patient who also failed all other closed techniques and needed open reduction. When compared with Allis (62% success rate), Whistler (60% success rate) and Captain Morgan (92% success rate) techniques, there was no statistically significant difference in the successfulness of the reduction techniques. There were no neurovascular or periprosthetic complications. We have described a reduction technique for posterior hip dislocations. Placing the patient's knee over the shoulder, and holding the lower leg like a 'Rocket Launcher' allow the physician's shoulder to work as a fulcrum, thus mechanically and ergonomically superior to standard techniques. © 2015 Australasian College for Emergency Medicine and Australasian Society for Emergency Medicine.

  18. Interfacial dislocation motion and interactions in single-crystal superalloys

    Energy Technology Data Exchange (ETDEWEB)

    Liu, B. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Raabe, D. [Max Planck Inst. fur Eisenforshung. Dusseldorf (Germany); Roters, F. [Max Planck Inst. fur Eisenforshung. Dusseldorf (Germany); Arsenlis, A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2014-10-01

    The early stage of high-temperature low-stress creep in single-crystal superalloys is characterized by the rapid development of interfacial dislocation networks. Although interfacial motion and dynamic recovery of these dislocation networks have long been expected to control the subsequent creep behavior, direct observation and hence in-depth understanding of such processes has not been achieved. Incorporating recent developments of discrete dislocation dynamics models, we simulate interfacial dislocation motion in the channel structures of single-crystal superalloys, and investigate how interfacial dislocation motion and dynamic recovery are affected by interfacial dislocation interactions and lattice misfit. Different types of dislocation interactions are considered: self, collinear, coplanar, Lomer junction, glissile junction, and Hirth junction. The simulation results show that strong dynamic recovery occurs due to the short-range reactions of collinear annihilation and Lomer junction formation. The misfit stress is found to induce and accelerate dynamic recovery of interfacial dislocation networks involving self-interaction and Hirth junction formation, but slow down the steady interfacial motion of coplanar and glissile junction forming dislocation networks. The insights gained from these simulations on high-temperature low-stress creep of single-crystal superalloys are also discussed.

  19. Dislocation kinetics and the acoustic-wave approximation for liquids

    International Nuclear Information System (INIS)

    Stout, R.B.

    1983-03-01

    A dislocation-dependent model for liquids describes the lattice deformation and the fluidity deformation as additive deformations. The lattice deformation represents distortions of an atom's potential energy structure and is a recoverable deformation response. The fluidity deformation represents discontinuous repositioning of atoms by dislocation kinetics in the lattice structure and is a nonrecoverable deformation response. From this model, one concludes that in liquids the acoustic-wave approximation is a description of a recoverable oscillation deformation that has dissipation because of dislocation kinetics. Other more-complex waves may exist, but such waves would rapidly disappear because of the small thermodynamic potential for dislocation kinetics in liquids

  20. Harmonic oscillator in an elastic medium with a spiral dislocation

    Science.gov (United States)

    Maia, A. V. D. M.; Bakke, K.

    2018-02-01

    We investigate the behaviour of a two-dimensional harmonic oscillator in an elastic medium that possesses a spiral dislocation (an edge dislocation). We show that the Schrödinger equation for harmonic oscillator in the presence of a spiral dislocation can be solved analytically. Further, we discuss the effects of this topological defect on the confinement to a hard-wall confining potential. In both cases, we analyse if the effects of the topology of the spiral dislocation gives rise to an Aharonov-Bohm-type effect for bound states.

  1. Dislocation and its recurrence after revision total hip arthroplasty.

    Science.gov (United States)

    Yoshimoto, Kensei; Nakashima, Yasuharu; Yamamoto, Takuaki; Fukushi, Jun-Ichi; Motomura, Goro; Ohishi, Masanobu; Hamai, Satoshi; Iwamoto, Yukihide

    2016-08-01

    Dislocation is a leading cause of failure after revision total hip arthroplasty (THA). This study was conducted to examine the risk factors for dislocation as well as their recurrence after revision THA. We retrospectively reviewed 178 revision THAs in 162 patients between 1998 and 2013. The mean patient age was 65.2 years at operation and the mean follow-up period was 6.7 years. Multivariate logistic regression was performed to identify risk factors for dislocation, and further comparison was made between patients with single and recurrent dislocations. Sixteen hips in 15 patients (9.0 %) dislocated at a mean of 9.1 months (range, 0-83 months) after revision THA. Multivariate analysis identified advanced age (odds ratio [OR] = 2.94/10 years) and osteonecrosis of the femoral head (OR = 7.71) as the independent risk factors for any dislocations. Risk factors for recurrent dislocations, which were observed in eight hips (50 %), were later dislocations (≥4 months) and lower BMI. Dislocation is a serious problem after revision THA with multiple risk factors. Although our findings were limited to revision THAs done through posterolateral approach, recognition of these factors is helpful in patient education and surgical planning.

  2. Dislocations and torsion in graphene and related systems

    International Nuclear Information System (INIS)

    Juan, Fernando de; Cortijo, Alberto; Vozmediano, Maria A.H.

    2010-01-01

    A continuum model to study the influence of dislocations on the electronic properties of condensed matter systems is described and analyzed. The model is based on a geometrical formalism that associates a density of dislocations with the torsion tensor and uses the technique of quantum field theory in curved space. When applied to two-dimensional systems with Dirac points like graphene we find that dislocations couple in the form of vector gauge fields similar to these arising from curvature or elastic strain. We also describe the ways to couple dislocations to normal metals with a Fermi surface.

  3. Dislocation and void segregation in copper during neutron irradiation

    DEFF Research Database (Denmark)

    Singh, Bachu Narain; Leffers, Torben; Horsewell, Andy

    1986-01-01

    High-purity (99. 999%) and fully annealed copper specimens have been irradiated in the DR-3 reactor at Riso to doses of 1 multiplied by 10**2**2 and 5 multiplied by 10**2**2 neutrons (fast)m** minus **2(2 multiplied by 10** minus **3 dpa and 1 multiplied by 10** minus **2 dpa, respectively...... were distributed between these walls. The dislocation walls were practically free of voids and generally had a void-denuded zone along them. The density of dislocations (loops and segments) was very low in the region containing voids (i. e. between the dislocation walls). Even with this low dislocation...

  4. Traumatic Anterior Dislocation of Hip in a Child- Case Report

    Directory of Open Access Journals (Sweden)

    S Ahmad

    2015-03-01

    Full Text Available Traumatic hip dislocation in children is relatively rare accounting for about 5% of all hip dislocations. Most of the hip dislocations seen in children are of the posterior type but the much rarer anterior and anterior-inferior (obturator types have also been described. We present the case of an eight years old girl with an obturator type of hip dislocation following trivial trauma. She was treated with closed reduction and immobilisation in skin traction for three weeks. She was followed up closely for one year and did not develop any complications during that period.

  5. Percutaneous osteosynthesis of Galeazzi fracture-dislocation.

    Science.gov (United States)

    Gadegone, Wasudeo M; Salphale, Yogesh; Magarkar, Ds

    2010-10-01

    A Galeazzi fracture is defined as a fracture of the radius associated with dislocation of the distal radio-ulnar joint (DRUJ). The conventional surgical technique of nailing does not give enough stability and open reduction, internal fixation with the plate is associated with numerous complications. The stacked nailing for the management of these injuries provides adequate stability, maintains the relationship of the DRUJ and promotes uneventful union by closed technique. The purpose of this study is to evaluate the results of simple, user-friendly, low cost elastic stacked nailing for the management of Galeazzi fracture dislocation. We treated 22 young adults with fresh Galeazzi fracture-dislocation of the forearm, from January 2004 to January 2008, by percutaneous fixation of fracture by stacked elastic nailing at our institute. There were 19 males and three females and the age group ranged from 20-56 years (average 35 years). Surgery was performed within 48 to 72 hours under the guidance of image intensifier. Medullary cavity was filled with two elastic titanium nails having unequal lengths and diameter. One nail acts as a reduction nail and the other acts as a stabilizing nail. The results were evaluated using Mikic criteria based on union, alignment, relationship of the DRUJ, and movements at the inferior radio ulnar joint, elbow and wrist. In six cases, following radiological union, nails in the radius were extracted between six to nine months after operation because of discomfort complained by the patient at site of insertion. After one year follow-up, 18 patients had excellent, four had fair results. Closed reduction and internal fixation of Galeazzi fracture by two elastic rods re-establishes the normal relationship of the fractured fragments and the DRUJ without repair of the ligaments. The stability is achieved by the flexibility and elasticity of the nails, crowding of the medullary canal and anchorage they gain in the radial diaphysis. Elastic nailing

  6. Bilateral Hip Dislocation in Unrestrained Driver

    Directory of Open Access Journals (Sweden)

    Samer Assaf

    2017-09-01

    Full Text Available History of present illness: A 24-year-old male was brought in by paramedics status post motor vehicle collision (MVC into an electric pole and tree at high speed. The patient was an unrestrained driver who required extrication. The patient complained of left hip pain, left foot pain, and difficulty extending his bilateral lower extremities. He denied numbness or tingling to his lower extremities. The patient had normal vitals; his bilateral lower extremities were held in flexion at the hips, but otherwise had no obvious injuries. The patient’s pelvis was stable with palpable distal pulses and intact motor and sensory function of his distal lower extremities. Significant findings: The initial radiograph of the pelvis revealed bilateral hip dislocations. Small bony fragments were noted in the right hip joint, suggestive of an underlying fracture. The sacroiliac joints and the pelvic ring were intact. In the emergency department, bilateral hip reductions were performed using the Captain Morgan technique.1 The post-reduction film showed reduction of the bilateral hip dislocations with extensive comminuted and displaced fractures of the right and left acetabula. Discussion: Bilateral hip dislocations are extremely rare, occurring in only 1% of all hip dislocations,2 and require immense force, typically occurring in MVCs (74%.3-7 Associated injuries include fracture of the acetabulum or femoral head, sciatic nerve damage, and obstruction of the blood supply to the femoral head.8 X-ray imaging and CT scans are used to assess the injury and to detect intra-articular fragments.3 Definitive treatment is achieved by closed reduction if possible; otherwise open reduction is utilized.9 Post-reduction therapy includes a non-weight-bearing period of time. Complications include avascular necrosis of the femoral head, osteonecrosis, and posttraumatic arthritis, the occurrence of which can be decreased by early reduction.4,10-12 This patient underwent bilateral

  7. Humeral shaft fracture with ipsilateral shoulder dislocation

    Directory of Open Access Journals (Sweden)

    Behera Prateek

    2014-02-01

    Full Text Available 【Abstract】Although fracture of the humeral shaft or dislocation of the shoulder joint is a common injury, a simutaneous injury is rare. We present such a case combined with head injury which took precedence over the skeletal injuries. The postoperative rehabilitation was slowed down by the head injury. This case report makes us aware of some problems when managing the patient with this rare injury and helps us understand the management options better. Also the need for proper follow-up and rehabilitation is emphasized.

  8. Why to climb if one can jump : a hill jumping algorithm for the vehicle routing problem with time windows

    NARCIS (Netherlands)

    Mester, David; Bräysy, Olli; Dullaert, Wout

    2018-01-01

    The most common approaches to solve the variants of the well-known vehicle routing problem are based on metaheuristic hill-climbing search. The deficiency of these methods is slow local search based hill climbing that often is restricted to limited local neighborhood. In this paper we suggest a

  9. Construct Validity and Test-Retest Reliability of the Climbing Stairs Questionnaire in Lower-Limb Amputees

    NARCIS (Netherlands)

    de Laat, Fred A.; Rommers, Gerardus M.; Geertzen, Jan H.; Roorda, Leo D.

    de Laat FA, Rommers GM, Geertzen JH, Roorda LD. Construct validity and test-retest reliability of the Climbing Stairs Questionnaire in lower-limb amputees. Arch Phys Med Rehabil 2010;91:1396-401. Objective: To investigate the construct validity and test-retest reliability of the Climbing Stairs

  10. Analysis of Relations between Spatiotemporal Movement Regulation and Performance of Discrete Actions Reveals Functionality in Skilled Climbing.

    Science.gov (United States)

    Orth, Dominic; Kerr, Graham; Davids, Keith; Seifert, Ludovic

    2017-01-01

    In this review of research on climbing expertise, we focus on different measures of climbing performance, including spatiotemporal measures related to fluency and activity states (i.e., discrete actions), adopted by climbers for achieving overall performance goals of getting to the end of a route efficiently and safely. Currently, a broad range of variables have been reported, however, many of these fail to capture how climbers adapt to a route whilst climbing. We argue that spatiotemporal measures should be considered concurrently with evaluation of activity states (such as reaching or exploring) in order gain a more comprehensive picture of how climbers successfully adapt to a route. Spatial and temporal movement measures taken at the hip are a traditional means of assessing efficiency of climbing behaviors. More recently, performatory and exploratory actions of the limbs have been used in combination with spatiotemporal indicators, highlighting the influence of limb states on climbing efficiency and skill transfer. However, only a few studies have attempted to combine spatiotemporal and activity state measures taken during route climbing. This review brings together existing approaches for observing climbing skill at performance outcome (i.e., spatiotemporal assessments) and process (i.e., limb activity states) levels of analysis. Skill level is associated with a spatially efficient route progression and lower levels of immobility. However, more difficult hold architecture designs require significantly greater mobility and more complex movement patterning to maintain performance. Different forms of functional, or goal-supportive, movement variability, including active recovery and hold exploration, have been implicated as important adaptations to physiological and environmental dynamics that emerge during the act of climbing. Indeed, recently it has also been shown that, when climbing on new routes, efficient exploration can improve the transfer of skill. This

  11. Analysis of Relations between Spatiotemporal Movement Regulation and Performance of Discrete Actions Reveals Functionality in Skilled Climbing

    Directory of Open Access Journals (Sweden)

    Dominic Orth

    2017-10-01

    Full Text Available In this review of research on climbing expertise, we focus on different measures of climbing performance, including spatiotemporal measures related to fluency and activity states (i.e., discrete actions, adopted by climbers for achieving overall performance goals of getting to the end of a route efficiently and safely. Currently, a broad range of variables have been reported, however, many of these fail to capture how climbers adapt to a route whilst climbing. We argue that spatiotemporal measures should be considered concurrently with evaluation of activity states (such as reaching or exploring in order gain a more comprehensive picture of how climbers successfully adapt to a route. Spatial and temporal movement measures taken at the hip are a traditional means of assessing efficiency of climbing behaviors. More recently, performatory and exploratory actions of the limbs have been used in combination with spatiotemporal indicators, highlighting the influence of limb states on climbing efficiency and skill transfer. However, only a few studies have attempted to combine spatiotemporal and activity state measures taken during route climbing. This review brings together existing approaches for observing climbing skill at performance outcome (i.e., spatiotemporal assessments and process (i.e., limb activity states levels of analysis. Skill level is associated with a spatially efficient route progression and lower levels of immobility. However, more difficult hold architecture designs require significantly greater mobility and more complex movement patterning to maintain performance. Different forms of functional, or goal-supportive, movement variability, including active recovery and hold exploration, have been implicated as important adaptations to physiological and environmental dynamics that emerge during the act of climbing. Indeed, recently it has also been shown that, when climbing on new routes, efficient exploration can improve the transfer

  12. Comparison of Genetic Algorithm and Hill Climbing for Shortest Path Optimization Mapping

    Directory of Open Access Journals (Sweden)

    Fronita Mona

    2018-01-01

    Full Text Available Traveling Salesman Problem (TSP is an optimization to find the shortest path to reach several destinations in one trip without passing through the same city and back again to the early departure city, the process is applied to the delivery systems. This comparison is done using two methods, namely optimization genetic algorithm and hill climbing. Hill Climbing works by directly selecting a new path that is exchanged with the neighbour’s to get the track distance smaller than the previous track, without testing. Genetic algorithms depend on the input parameters, they are the number of population, the probability of crossover, mutation probability and the number of generations. To simplify the process of determining the shortest path supported by the development of software that uses the google map API. Tests carried out as much as 20 times with the number of city 8, 16, 24 and 32 to see which method is optimal in terms of distance and time computation. Based on experiments conducted with a number of cities 3, 4, 5 and 6 producing the same value and optimal distance for the genetic algorithm and hill climbing, the value of this distance begins to differ with the number of city 7. The overall results shows that these tests, hill climbing are more optimal to number of small cities and the number of cities over 30 optimized using genetic algorithms.

  13. Comparison of Genetic Algorithm and Hill Climbing for Shortest Path Optimization Mapping

    Science.gov (United States)

    Fronita, Mona; Gernowo, Rahmat; Gunawan, Vincencius

    2018-02-01

    Traveling Salesman Problem (TSP) is an optimization to find the shortest path to reach several destinations in one trip without passing through the same city and back again to the early departure city, the process is applied to the delivery systems. This comparison is done using two methods, namely optimization genetic algorithm and hill climbing. Hill Climbing works by directly selecting a new path that is exchanged with the neighbour's to get the track distance smaller than the previous track, without testing. Genetic algorithms depend on the input parameters, they are the number of population, the probability of crossover, mutation probability and the number of generations. To simplify the process of determining the shortest path supported by the development of software that uses the google map API. Tests carried out as much as 20 times with the number of city 8, 16, 24 and 32 to see which method is optimal in terms of distance and time computation. Based on experiments conducted with a number of cities 3, 4, 5 and 6 producing the same value and optimal distance for the genetic algorithm and hill climbing, the value of this distance begins to differ with the number of city 7. The overall results shows that these tests, hill climbing are more optimal to number of small cities and the number of cities over 30 optimized using genetic algorithms.

  14. Climbing fiber-evoked endocannabinoid signaling heterosynaptically suppresses presynaptic cerebellar long-term potentiation

    NARCIS (Netherlands)

    B.J. van Beugen (Boeke); R.Y. Nagaraja (Raghavendra); C.R.W. Hansel (Christian)

    2006-01-01

    textabstractEndocannabinoid signaling has been demonstrated to mediate depolarization-induced suppression of excitation at climbing fiber (CF) and parallel fiber (PF) synapses onto cerebellar Purkinje cells. Here, we show that CF-evoked release of cannabinoids (CBs) additionally suppresses a

  15. Foot clearance strategy for step-over-step stair climbing in transfemoral amputees.

    Science.gov (United States)

    Hobara, Hiroaki; Kobayashi, Yoshiyuki; Nakamura, Takashi; Yamasaki, Nobuya; Ogata, Toru

    2014-08-01

    Stair ascent is a particularly challenging task for transfemoral amputees. The aim of this clinical note was to describe the kinematic features of foot clearance in transfemoral amputee who can ascend stairs using a step-over-step strategy. The marker trajectories of the first metatarsophalangeal joint (Mt1) and clearance height were measured in two transfemoral amputees who could (TF1) and could not (TF2) climb stairs using a step-over-step strategy. The Mt1 marker trajectories of the TF1 moved backward in the early swing phase, and the trajectory followed an off-centered parabolic arc to achieve a similar clearance height as able-bodied subjects. TF2 could not climb the stairs without tripping in each step. An effective compensatory strategy to avoid tripping during stair climbing may be to use the hip joint for a backward extension and rapid flexion of the prosthetic leg during the early swing phase. The foot clearance strategy in transfemoral amputees who can climb stairs using a step-over-step strategy will help us better understand adaptive prosthetic control and thus develop more effective gait rehabilitation programs. © The International Society for Prosthetics and Orthotics 2013.

  16. Ask Dr. Sue: Tree Climbing and Care of Sand Play Areas.

    Science.gov (United States)

    Aronson, Susan S.

    1993-01-01

    Discusses safety aspects of tree climbing and the use of sand in outdoor play areas at day care centers. Specifies ways to prune trees so that they are unclimbable and methods for maintaining sand areas. Includes a recipe for sand disinfectant. (MDM)

  17. Transition Analysis and Its Application to Global Path Determination for a Biped Climbing Robot

    Directory of Open Access Journals (Sweden)

    Haifei Zhu

    2018-01-01

    Full Text Available Biped climbing robots are considered good assistants and (or substitutes for human workers carrying out high-rise truss-associated routine tasks. Flexible locomotion on three-dimensional complex trusses is a fundamental skill for these robots. In particular, the capability to transit from one structural member to another is paramount for switching objects to be climbed upon. In this paper, we study member-to-member transition and its utility in global path searching for biped climbing robots. To compute operational regions for transition, hierarchical inspection of safety, reachability, and accessibility of grips is taken into account. A novel global path rapid determination approach is subsequently proposed based on the transition analysis. This scheme is efficient for finding feasible routes with respect to the overall structural environment, which also benefits the subsequent grip and motion planning. Simulations are conducted with Climbot, our self-developed biped climbing robot, to verify the efficiency of the presented method. Results show that our proposed method is able to accurately determine the operational region for transition within tens of milliseconds and can obtain global paths within seconds in general.

  18. 77 FR 33777 - General Aviation Safety Forum: Climbing to the Next Level

    Science.gov (United States)

    2012-06-07

    ... NATIONAL TRANSPORTATION SAFETY BOARD General Aviation Safety Forum: Climbing to the Next Level The National Transportation Safety Board (NTSB) will convene a 2- day forum focused on safety issues related to... the Next Level,'' will be chaired by NTSB Chairman Deborah A. P. Hersman and all five Board Members...

  19. Risk of transmission of blood borne infections in climbing--consensus statement of UIAA Medcom.

    Science.gov (United States)

    Schöffl, V; Morrison, A; Küpper, T

    2011-03-01

    Blood borne infections such as hepatitis B, C (HBV, HBC) and human immunodeficiency disease (HIV) are major health problems globally. As the number of blood borne infections is postulated to increase among athletes, the question to the UIAA Medical Commission arises as to whether there is a risk of transmission in climbing. Using a nominal group consensus model approach a working group was formed during the UIAA Medical Commission's meeting in Adršpach-Zdoóov, in the Czech Republic, 2008. A working document was prepared and circulated via email. After several revisions the following final form was approved by written consent in lieu of a live meeting of the UIAA MedCom on 31st May, 2010: The main pathways of transmission of blood borne infections in athletes are similar to those experienced in the general population. The greatest risk to the athlete for contracting any blood borne pathogen infection is through sexual activity and parenteral drug use, and not in the sporting arena. The transmission risk in climbing is even smaller compared to contact sports. Mandatory HIV, HBV or HCV testing or widespread screening is not recommended, voluntary testing is recommended for all high risk athletes in the same way as for non-athletes. HIV and HBV positive climbers should not be banned from climbing or climbing competitions. The risk of transmission from infected athletes to other athletes is very low, the focus should be on preventive activities and education. © Georg Thieme Verlag KG Stuttgart · New York.

  20. EBSD analysis of subgrain boundaries and dislocation slip systems in Antarctic and Greenland ice

    Science.gov (United States)

    Weikusat, Ilka; Kuiper, Ernst-Jan N.; Pennock, Gill M.; Kipfstuhl, Sepp; Drury, Martyn R.

    2017-09-01

    Ice has a very high plastic anisotropy with easy dislocation glide on basal planes, while glide on non-basal planes is much harder. Basal glide involves dislocations with the Burgers vector b = 〈a〉, while glide on non-basal planes can involve dislocations with b = 〈a〉, b = [c], and b = 〈c + a〉. During the natural ductile flow of polar ice sheets, most of the deformation is expected to occur by basal slip accommodated by other processes, including non-basal slip and grain boundary processes. However, the importance of different accommodating processes is controversial. The recent application of micro-diffraction analysis methods to ice, such as X-ray Laue diffraction and electron backscattered diffraction (EBSD), has demonstrated that subgrain boundaries indicative of non-basal slip are present in naturally deformed ice, although so far the available data sets are limited. In this study we present an analysis of a large number of subgrain boundaries in ice core samples from one depth level from two deep ice cores from Antarctica (EPICA-DML deep ice core at 656 m of depth) and Greenland (NEEM deep ice core at 719 m of depth). EBSD provides information for the characterization of subgrain boundary types and on the dislocations that are likely to be present along the boundary. EBSD analyses, in combination with light microscopy measurements, are presented and interpreted in terms of the dislocation slip systems. The most common subgrain boundaries are indicative of basal 〈a〉 slip with an almost equal occurrence of subgrain boundaries indicative of prism [c] or 〈c + a〉 slip on prism and/or pyramidal planes. A few subgrain boundaries are indicative of prism 〈a〉 slip or slip of 〈a〉 screw dislocations on the basal plane. In addition to these classical polygonization processes that involve the recovery of dislocations into boundaries, alternative mechanisms are discussed for the formation of subgrain boundaries that are not related to the

  1. Environmental design shapes perceptual-motor exploration, learning and transfer in climbing

    Directory of Open Access Journals (Sweden)

    Ludovic eSeifert

    2015-11-01

    Full Text Available This study investigated how environmental design shapes perceptual-motor exploration, when meta-stable regions of performance are created. Here, we examined how creating meta-stable regions of performance could destabilize pre-existing skills, favoring greater exploration of performance environments, exemplified in this study by climbing surfaces. In this investigation we manipulated hold orientations on an indoor climbing wall to examine how nine climbers explored, learned and transferred various trunk-rolling motion patterns and hand grasping movements. The learning protocol consisted of four sessions, in which climbers randomly ascended three different routes, as fluently as possible. All three routes were 10.3m in height and composed of 20 hand-holds at the same locations on an artificial climbing wall; only hold orientations were altered: (i a horizontal-edge route was designed to afford horizontal hold grasping, (ii a vertical-edge route afforded vertical hold grasping, and (iii, a double-edge route was designed to afford both horizontal and vertical hold grasping. As a meta-stable condition of performance invite an individual to both exploit his pre-existing behavioral repertoire (i.e., horizontal hold grasping pattern and trunk face to the wall and explore new behaviors (i.e., vertical hold grasping and trunk side to the wall, it was hypothesized that the double-edge route characterized a meta-stable region of performance. Data were collected from inertial measurement units located on the neck and hip of each climber, allowing us to compute rolling motion referenced to the artificial climbing wall. Information on ascent duration, the number of exploratory and performatory movements for locating hand-holds, and hip path was also observed in video footage from a frontal camera worn by participants. Climbing fluency was assessed by calculating geometric index of entropy. Results showed that the meta-stable condition of performance may have

  2. Temporomandibular joint dislocation in an epileptic and mentally ...

    African Journals Online (AJOL)

    Temporomandibular joint (TMJ) dislocation is defined as an excessive forward movement of the condyle beyond the articular eminence with complete separation of articular surfaces and fixation in that position.' Theories regarding the pathogenesis of TMJ dislocation propose laxity of TMJ ligaments or capsule, excessive ...

  3. Dislocation multiplication rate in the early stage of germanium plasticity

    Czech Academy of Sciences Publication Activity Database

    Fikar, J.; Dupas, Corinne; Kruml, Tomáš; Jacques, A.; Martin, J. L.

    400-401, - (2005), s. 431-434 ISSN 0921-5093. [Dislocations 2004. La Colle-sur-Loup, 13.09.2004-17.09.2004] Institutional research plan: CEZ:AV0Z2041904 Keywords : dislocation multiplication * germanium * constitutive modelling Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.347, year: 2005

  4. Management of neglected traumatic posterior dislocations of the hip ...

    African Journals Online (AJOL)

    Within a period of six months, three men were admitted following falls which had occurred more than one week previously. They had all sustained minor trauma but directly after the injury they were unable to bear weight on the affected limb. All three had Grade 1 posterior dislocations of the hip. Although the dislocation had ...

  5. Ipsilateral dislocation of the shoulder and elbow: A case report

    African Journals Online (AJOL)

    Pr KODO

    There was deformity and painful swelling of the right shoulder and elbow. No neurovascular deficit was found and other clinical. findings were normal. Plain radiograph revealed ipsilateral anterior shoulder and posterior elbow dislocations (Fig 1). Under general anesthesia, the dislocations were readily reduced by closed.

  6. Dislocated ankle fracture complicated by near total distal ischaemia

    Science.gov (United States)

    Duygun, Fatih; Sertkaya, Omer; Aldemir, Cengiz; Dogan, Ali

    2013-01-01

    Total arterial ischaemia is rarely seen following a dislocated ankle fracture but if it does and intervention is not made, it can lead to serious morbidity. We present a 39-year-old woman with almost total occlusion in the arteria tibialis and arteria dorsalis pedis following a dislocated ankle fracture as a result of a bicycle fall. PMID:24248319

  7. Perineal anterior dislocation of the hip with avulsion fracture of ...

    African Journals Online (AJOL)

    Traumatic anterior dislocation of the hip is rare even in children. Very uncommon also is the perineal variant of the inferior type of anterior dislocation with concomitant avulsion fracture of the greater trochanter. We report such a case highlighting the peculiarity of its management. No similar case of triumvirate injury of the hip ...

  8. Results of open reduction for neglected elbow dislocations in adult ...

    African Journals Online (AJOL)

    Objective: To present the results of open reduction of neglected elbow dislocations using a consistent surgical protocol. Patients and methods: Between 2000 and 2005 eight patients with neglected elbow dislocations were operated on using the Speed\\'s posterior approach with lengthening of the triceps by V-Y ...

  9. Isolated posterior dislocation of the radial head in an adult.

    Directory of Open Access Journals (Sweden)

    Negi A

    1992-07-01

    Full Text Available Isolated posterior dislocation of the radial head was detected on X-ray in a patient following a vehicular accident. Such a dislocation without an associated fracture is extremely rare in adults. Immobilization of the elbow in full pronation and 90 degrees flexion for 4 weeks normalized the position of the head of the radius.

  10. Pediatric open elbow dislocation without fracture: A case report

    Directory of Open Access Journals (Sweden)

    Gökhan Polat

    2014-01-01

    CONCLUSION: Pediatric elbow dislocations are rare injuries and the management of these injuries can be technically demanding due to concurrent neurovascular injuries. An open dislocation without fracture is very rare and it should be treated with immediate intervention, an effective teamwork and good rehabilitation.

  11. A Monte Carlo adapted finite element method for dislocation ...

    Indian Academy of Sciences (India)

    Mean and standard deviation values, as well as probability density function of ground surface responses due to the dislocation are computed. Based on analytical and numerical calculation of dislocation, two approaches of Monte Carlo simulations are proposed. Various comparisons are examined to illustrate the capability ...

  12. Superior dislocation hip with anterior column acetabular fracture ...

    African Journals Online (AJOL)

    Superior variety of anterior dislocation of the hip is a rare injury. Its occurrence with acetabular fractures has been documented infrequently. We report a case of superior dislocation of the hip with anterior column acetabular fracture. Open reduction of the hip and internal fixation of the fracture was carried out using a twin ...

  13. Exploring the Limit of Dislocation Based Plasticity in Nanostructured Metals

    DEFF Research Database (Denmark)

    Hughes, D. A.; Hansen, Niels

    2014-01-01

    A twofold decrease to an unexplored scale of 5 nm was produced in Cu by applying a large sliding load in liquid nitrogen. Statistical and universal scaling analyses of deformation induced high angle boundaries, dislocation boundaries, and individual dislocations observed by high resolution electr...

  14. Method to reduce dislocation density in silicon using stress

    Science.gov (United States)

    Buonassisi, Anthony; Bertoni, Mariana; Argon, Ali; Castellanos, Sergio; Fecych, Alexandria; Powell, Douglas; Vogl, Michelle

    2013-03-05

    A crystalline material structure with reduced dislocation density and method of producing same is provided. The crystalline material structure is annealed at temperatures above the brittle-to-ductile transition temperature of the crystalline material structure. One or more stress elements are formed on the crystalline material structure so as to annihilate dislocations or to move them into less harmful locations.

  15. Traumatic posterior dislocation of the hip: distribution and severity of ...

    African Journals Online (AJOL)

    These injuries take precedence in the emergency care of patients with posterior dislocation of the hip. The role of public enlightment on road safety measures cannot be over-emphasized and a case is made for training of the populace in essential basic life support. Keywords: Posterior hip dislocation; associated injuries; ...

  16. Rows of Dislocation Loops in Aluminium Irradiated by Aluminium Ions

    DEFF Research Database (Denmark)

    Henriksen, L.; Johansen, A.; Koch, J.

    1967-01-01

    Single-crystal aluminium specimens, irradiated with 50-keV aluminium ions, contain dislocation loops that are arranged in regular rows along <110 > directions. ©1967 The American Institute of Physics......Single-crystal aluminium specimens, irradiated with 50-keV aluminium ions, contain dislocation loops that are arranged in regular rows along directions. ©1967 The American Institute of Physics...

  17. Self-force on dislocation segments in anisotropic crystals

    International Nuclear Information System (INIS)

    Fitzgerald, S P; Aubry, S

    2010-01-01

    A dislocation segment in a crystal experiences a 'self-force', by virtue of the orientation dependence of its elastic energy. If the crystal is elastically isotropic, this force is manifested as a couple acting to rotate the segment toward the lower energy of the pure screw orientation (i.e. acting to align the dislocation line with its Burgers vector). If the crystal is anisotropic, there are additional contributions to the couple, arising from the more complex energy landscape of the lattice itself. These effects can strongly influence the dynamic evolution of dislocation networks, and via their governing role in dislocation multiplication phenomena, control plastic flow in metals. In this paper we develop a model for dislocation self-forces in a general anisotropic crystal, and briefly consider the technologically important example of α-iron, which becomes increasingly anisotropic as the temperature approaches that of the α-γ phase transition at 912 0 C.

  18. Atlantoaxial dislocation with special emphasis on computed tomography findings

    Energy Technology Data Exchange (ETDEWEB)

    Miyasaka, Kazuo; Isu, Toyohiko; Abe, Satoru; Takei, Hidetoshi; Irie, Goro

    1983-01-01

    In this study, the authors evaluated the effectiveness of computed tomography (CT) in the diagnosis of atlantoaxial dislocation (AAD). On the basis of CT evidence of Cl-2 interrelationship, AAD in 26 patients was classified into 4 major types; anteroposterior dislocation in 13 patients, transverse dislocation in 2, anteroposterior-transverse dislocation in 3, and rotatory dislocation in 8. A thick wad of soft tissue on the posterior aspect of the odontoid was found in as many as 38% of the patients and related to compromise the spinal canal. Association of atlantooccipital subluxation with AAD was not rarely encountered in this series (6 out of 26 patients). CT can most optimally and noninvasively demonstrate relationship among the occipitoatlanto-axial complex and associated soft tissue abnormalities. (author).

  19. 77 FR 50207 - Notice of Final Federal Agency Actions on Project: I-5: Glendale-Hugo Paving/Sexton Climbing Lane...

    Science.gov (United States)

    2012-08-20

    ... Paving/Sexton Climbing Lane: Douglas and Josephine Counties, OR AGENCY: Federal Highway Administration... relate to a proposed highway project, I-5: Glendale-Hugo Paving/Sexton Climbing Lane, in Douglas and...) 231- 2336. The I-5: Glendale-Hugo Paving/Sexton Climbing Lane categorical exclusion and other project...

  20. Low-Energy Dislocation Structure (LEDS) character of dislocation boundaries aligned with slip planes in rolled aluminium

    DEFF Research Database (Denmark)

    Winther, Grethe; Hong, Chuanshi; Huang, Xiaoxu

    2015-01-01

    For the specific slip geometry of two sets of coplanar systems (a total of four systems) in fcc metals, the range of dislocation networks in boundaries aligned with one of the two active slip planes is predicted from the Frank equation for boundaries free of long-range elastic stresses. Detailed...... by dislocation reactions. Cross slip plays a role in the boundary formation process....

  1. Ab initio simulation of dislocation cores in metals; Simulation ab initio des coeurs de dislocation dans les metaux

    Energy Technology Data Exchange (ETDEWEB)

    Ventelon, L. [CEA Saclay, Dept. des Materiaux pour le Nucleaire (DEN/DANS/DMN/SRMP), 91 - Gif-sur-Yvette (France)

    2008-07-01

    In the framework of the multi scale simulation of metals and alloys plasticity, the aim of this study is to develop a methodology of ab initio dislocations study and to apply it to the [111] screw dislocation in the bc iron. (A.L.B.)

  2. Aspects of dislocation substructures associated with the deformation stages of stainless steel AISI 304 at high temperatures

    International Nuclear Information System (INIS)

    Oliveira, J.L.L.; Reis Filho, J.A.B.S.; Almeida, L.H. de; Monteiro, S.N.

    1978-07-01

    The development of dislocation substrutures in type 304 austenitic stainless steel at high temperatures has been associated with the deformation stages through log dσ/d epsilon x log epsilon plots, which show the transition point independently. The mechanisms responsible for the Dynamic Strain Aging particulary the Portevin-LeChatelier effect were related to the appearence of the stages. The results indicate that the deformation stages can be divided into two distinct regions. Each one of these region show particular characteristics with respect to the stress level, transition point, developed substructure and type of crystalline defects interaction with dislocations. (Author) [pt

  3. Erratic Dislocations within Funnel Defects in AlN Templates for AlGaNEpitaxial Layer Growth

    Energy Technology Data Exchange (ETDEWEB)

    Hawkridge, Michael E; Liliental-Weber, Zuzanna; Jin Kim, Hee; Choi, Suk; Yoo, Dongwon; Ryou, Jae-Hyun; Dupuis, Russel D

    2009-03-13

    We report our transmission electron microscopy observations of erraticdislocation behavior within funnel-like defects in the top of AlN templates filled withAlGaN from an overlying epitaxial layer. This dislocation behavior is observed inmaterial where phase separation is also observed. Several bare AlN templates wereexamined to determine the formation mechanism of the funnels. Our results suggest that they are formed prior to epitaxial layer deposition due to the presence of impuritiesduring template re-growth. We discuss the erratic dislocation behavior in relation to thepresence of the phase-separated material and the possible effects of these defects on the optoelectronic properties.

  4. Screw dislocations in complex, low symmetry oxides: core structures, energetics, and impact on crystal growth.

    Science.gov (United States)

    Shahsavari, Rouzbeh; Chen, Lu

    2015-02-04

    Determining the atomic structure and the influence of defects on properties of low symmetry oxides have long been an engineering pursuit. Here, we focus on five thermodynamically reversible monoclinic and orthorhombic polymorphs of dicalcium silicates (Ca2SiO3)-a key cement constituent-as a model system and use atomistic simulations to unravel the interplay between the screw dislocation core energies, nonplanar core structures, and Peierls stresses along different crystallographic planes. Among different polymorphs, we found that the α polymorphs (α-C2S) has the largest Peierls stress, corresponding to the most brittle polymorph, which make it attractive for grinding processes. Interestingly, our analyses indicate that this polymorphs has the lowest dislocation core energy, making it ideal for reactivity and crystal growth. Generally, we identified the following order in terms of grinding efficiency based on screw dislocation analysis, α-C2S > αH-C2S > αL-C2S > β-C2S > γ-C2S, and the following order in term of reactivity, α -C2S > αL-C2S > γ-C2S > αH-C2S > β-C2S. This information, combined with other deformation-based mechanisms, such as twinning and edge dislocation, can provide crucial insights and guiding hypotheses for experimentalists to tune the cement grinding mechanisms and reactivity processes for an overall optimum solution with regard to both energy consumption and performance. Our findings significantly broaden the spectrum of strategies for leveraging both crystallographic directions and crystal symmetry to concurrently modulate mechanics and crystal growth processes within an identical chemical composition.

  5. Dislocation mechanism of twinning in Ni-Mn-Ga

    Czech Academy of Sciences Publication Activity Database

    Zárubová, Niva; Ge, Y.; Gemperlová, Juliana; Gemperle, Antonín; Hannula, S.-P.

    2012-01-01

    Roč. 5, č. 1 (2012), "1250006-1"-"1250006-4" ISSN 1793-6047 R&D Projects: GA ČR GAP107/10/0824; GA ČR(CZ) GAP107/11/0391; GA AV ČR IAA100100920 Institutional research plan: CEZ:AV0Z10100520 Keywords : Ni-Mn-Ga shape memory alloy * martensitic transformation * in situ TEM straining Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.270, year: 2012

  6. Slip dislocation and twin nucleation mechanisms in hcp metals

    Czech Academy of Sciences Publication Activity Database

    Ostapovets, Andriy; Serra, A.

    2017-01-01

    Roč. 52, č. 1 (2017), s. 533-540 ISSN 0022-2461 R&D Projects: GA MŠk(CZ) LQ1601 Institutional support: RVO:68081723 Keywords : Defects * Shear stress * Stacking faults Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 2.599, year: 2016

  7. Positron-trapping mechanism at dislocations in Zn

    DEFF Research Database (Denmark)

    Hidalgo, Carlos; Linderoth, Søren; Diego, Nieves de

    1987-01-01

    The evolution of the positron-lifetime parameters with the measuring temperature has been studied in deformed Zn in the temperature range 12–210 K. For two samples with different degrees of deformation the presence of a component with a lifetime close to that in a monovacancy is observed. Both th...

  8. Radiation-induced strengthening and absorption of dislocation loops in ferritic Fe-Cr alloys: the role of Cr segregation.

    Science.gov (United States)

    Terentyev, D; Bakaev, A

    2013-07-03

    The understanding of radiation-induced strengthening in ferritic FeCr-based steels remains an essential issue in the assessment of materials for fusion and fission reactors. Both early and recent experimental works on Fe-Cr alloys reveal Cr segregation on radiation-induced nanostructural features (mainly dislocation loops), whose impact on the modification of the mechanical response of the material might be key for explaining quantitatively the radiation-induced strengthening in these alloys. In this work, we use molecular dynamics to study systematically the interaction of dislocations with 1/2 and loops in all possible orientations, both enriched by Cr atoms and undecorated, for different temperatures, loop sizes and dislocation velocities. The configurations of the enriched loops have been obtained using a non-rigid lattice Monte Carlo method. The study reveals that Cr segregation influences the interaction mechanisms with both 1/2 and loops. The overall effect of Cr enrichment is to penalize the mobility of intrinsically glissile 1/2 loops, modifying the reaction mechanisms as a result. The following three most important effects associated with Cr enrichment have been revealed: (i) absence of dynamic drag; (ii) suppression of complete absorption; (iii) enhanced strength of small dislocation loops (2 nm and smaller). Overall the effect of the Cr enrichment is therefore to increase the unpinning stress, so experimentally 'invisible' nanostructural features may also contribute to radiation-induced strengthening. The reasons for the modification of the mechanisms are explained and the impact of the loading conditions is discussed.

  9. Dislocation Structures in Nickel Based Superalloy Inconel 792-5A Fatigued at Room Temperature and 700 °C

    Czech Academy of Sciences Publication Activity Database

    Petrenec, Martin; Obrtlík, Karel; Polák, Jaroslav; Man, Jiří

    2008-01-01

    Roč. 567-568, - (2008), s. 429-432 ISSN 0255-5476. [MSMF /5./. Brno, 27.06.2007-29.06.2007] R&D Projects: GA ČR(CZ) GP106/05/P521 Institutional research plan: CEZ:AV0Z20410507 Keywords : Low cycle fatigue * superalloy * dislocation structure Subject RIV: JL - Materials Fatigue, Friction Mechanics

  10. Orowan strengthening and forest hardening superposition examined by dislocation dynamics simulations

    International Nuclear Information System (INIS)

    Queyreau, Sylvain; Monnet, Ghiath; Devincre, Benoit

    2010-01-01

    Rule of mixtures are an essential feature of the modeling of plastic deformation in complex materials in which more than one strain-hardening mechanism is involved. In this work, use is made of dislocation dynamics simulations to characterize the individual and the superposed contributions of two major mechanisms of crystal plasticity, i.e. Orowan strengthening and forest hardening. Based on a formal description of each hardening mechanism, evidence is presented to show that a quadratic rule of mixtures has the ability to predict quantitatively the flow stress of complex materials such as reactor pressure vessel steel.

  11. Acceleration of the Particle Swarm Optimization for Peierls-Nabarro modeling of dislocations in conventional and high-entropy alloys

    Science.gov (United States)

    Pei, Zongrui; Eisenbach, Markus

    2017-06-01

    Dislocations are among the most important defects in determining the mechanical properties of both conventional alloys and high-entropy alloys. The Peierls-Nabarro model supplies an efficient pathway to their geometries and mobility. The difficulty in solving the integro-differential Peierls-Nabarro equation is how to effectively avoid the local minima in the energy landscape of a dislocation core. Among the other methods to optimize the dislocation core structures, we choose the algorithm of Particle Swarm Optimization, an algorithm that simulates the social behaviors of organisms. By employing more particles (bigger swarm) and more iterative steps (allowing them to explore for longer time), the local minima can be effectively avoided. But this would require more computational cost. The advantage of this algorithm is that it is readily parallelized in modern high computing architecture. We demonstrate the performance of our parallelized algorithm scales linearly with the number of employed cores.

  12. Stress field of a dislocating inclined fault

    Energy Technology Data Exchange (ETDEWEB)

    Huang, F.; Wang, T.

    1980-02-01

    Analytical expressions are derived for the stress field caused by a rectangular dislocating fault of an arbitrary dip in a semi-infinite elastic medium for the case of unequal Lame constants. The results of computations for the stress fields on the ground surface of an inclined strike-slip and an inclined dip-slip fault are represented by contour maps. The effects of Poisson Ratio of the medium, the dip angle, upper and lower boundaries of the faults on the stress field at surface have been discussed. As an application, the contour maps for shear stress and hydrostatic stress of near fields of the Tonghai (1970), Haicheng (1975) and Tangshan (1976) earthquakes have been calculated and compared with the spatial distributions of strong aftershocks of these earthquakes. It is found that most of the strong aftershocks are distributed in the regions of tensional stress, where the hydrostatic stress is positive.

  13. Stress field of a dislocating inclined fault

    Energy Technology Data Exchange (ETDEWEB)

    Huang, F.; Wang, T.

    1980-02-01

    In this paper, analytical expressions of the stress field given rise by a rectangular dislocating fault of an arbitrary dip in a semi-infinite elastic medium for the case of unequal Lame constants are derived. The results of computations for the stress fields on the ground surface of an inclined strike-slip and an inclined dip-slip fault are represented by contour maps. The effects of the Poisson Ratio of the medium, the dip angle, upper and lower boundaries of the faults on the stress field at the surface have been discussed. As an application, the contour maps for shear stress and hydrostatic stress of near fields of the Tonghai (1970), Haicheng, (1975) and Tangshan (1976) earthquakes have been calculated and compared with the spatial distributions of strong aftershocks of these earthquakes. It is found that most of the strong aftershocks are distributed in the regions of tensional stress where the hydrostatic stress is positive.

  14. Dual mobility cup in revision total hip arthroplasty: dislocation rate and survival after 5 years.

    Science.gov (United States)

    Simian, E; Chatellard, R; Druon, J; Berhouet, J; Rosset, P

    2015-09-01

    Dislocation is a common complication of total hip arthroplasty (THA), particularly when performed as revision surgery. Dual mobility cups (DMCs) minimize the risk of instability when implanted during primary THA. However, their usefulness and survival in revision THA remain unclear. We therefore conducted a retrospective study to assess DMC stability and survival at a minimal follow-up period of 5years after revision THA. The dislocation rate associated with DMCs for revision THA is similar to that seen after primary THA. Cup exchange with implantation of a DMC was performed in 71 patients (74 hips) between 2000 and 2007, for the following reasons: recurrent dislocation (n=22), aseptic loosening (n=38), and infection (n=14). The DMCs were cemented in 47 cases and cementless in 27 cases. The clinical variables (Merle d'Aubigné-Postel score and Harris Hip Score) and radiological findings were collected retrospectively from the medical records and compared with those obtained at the last follow-up visit. Of the 74 cases, 2 were lost to follow-up. At last follow-up, the mean Merle d'Aubigné-Postel score was 15.2 (11-18) and the mean Harris Hip Score was 80.4 (51-98). Of the 8 failures, 2 (2/72, 2.7%) were related to mechanical factors (1 case each of aseptic loosening and dislocation) and 6 were changed because of infection (recurrent infection, n=4). Mechanical failure was not linked to a specific reason for revision THA. A radiolucent line was visible in 4 cases but this finding was not associated with clinical manifestations. When failure was defined as cup revision for any non-infectious complication, 5-year implant survival was 99% (95% confidence interval, 93-100%). Use of a DMC in revision THA was associated with a slightly higher dislocation rate (1/72, 1.4%) than in primary THA, whereas 5-year survival was comparable. Cemented DMCs were not associated with a greater risk of loosening. DMCs are useful to decrease the risk of dislocation in revision THA

  15. The effects of high resistance-few repetitions and low resistance-high repetitions resistance training on climbing performance.

    Science.gov (United States)

    Hermans, Espen; Andersen, Vidar; Saeterbakken, Atle Hole

    2017-05-01

    The aim of the study was to compare the effects of different strength training intensities on climbing performance, climbing-specific tests and a general strength test. Thirty lower grade and intermediate-level climbers participated in a 10-week training programme. The participants were randomized into three groups: high resistance-few repetitions training groups (HR-FR), low resistance-high repetitions training groups (LR-HR) and a control group (CON) which continued climbing/training as usual. Post-testing results demonstrated statistical tendencies for climbing performance improvements in the HR-FR and LR-HR (p = 0.088-0.090, effect size = 0.55-0.73), but no differences were observed between the groups (p = 0.950). For the climbing-specific tests, no differences were observed between the groups (p = 0.507-1.000), but the HR-FR and LR-HR improved their time in both Dead-hang (p = 0.004-0.026) and Bent-arm hang (p training groups reduced their climbing sessions during the intervention compared to the CON group (p = 0.057-0.074). In conclusion, HR-FR and LR-HR training programmes demonstrated an 11% and 12% non-significant improvement in climbing performance despite a 50% reduction in climbing sessions, but improved the results in strength and climbing-specific tests. None of the training intensities was superior compared to the others.

  16. Concept of healing of recurrent shoulder dislocation

    Directory of Open Access Journals (Sweden)

    Donato D'Angelo

    2014-08-01

    Full Text Available This paper presents the main surgical techniques applied in the treatment of anterior recurrent shoulder dislocation, aiming the achievement of the normality of articulate movements. This was obtained by combining distinct surgical procedures, which allowed the recovery of a complete functional capacity of the shoulder, without jeopardizing the normality of movement, something that has not been recorded in the case of the tense sutures of the surgical procedures of Putti-Platt, Bankart, Latarjet, Dickson-O'Dell and others.The careful review of the methods applied supports the conclusion that recurrent shoulder dislocation can be cured, since cure has been obtained in 97% of the treated cases. However, some degree of limitation in the shoulder movement has been observed in most of the treated cases.Our main goal was to achieve a complete shoulder functional recovery, by treating simultaneously all of the anatomical–pathological lesions, without considering the so-called essential lesions.The period of post-operatory immobilization only last for the healing of soft parts; this takes place in a position of neutral shoulder rotation, since the use of vascular bone graft eliminates the need for long time immobilization, due to the shoulder stabilization provided by rigid fixation of the coracoid at the glenoid edge, as in the Latarjet's technique.Our procedure, used since 1959, comprises the association of several techniques, which has permitted shoulder healing without movement limitation. That was because of the tension reduction in the sutures of the subescapularis, capsule, and coracobraquialis muscles.

  17. Human climbing with efficiently scaled gecko-inspired dry adhesives

    OpenAIRE

    Hawkes, Elliot W.; Eason, Eric V.; Christensen, David L.; Cutkosky, Mark R.

    2015-01-01

    Since the discovery of the mechanism of adhesion in geckos, many synthetic dry adhesives have been developed with desirable gecko-like properties such as reusability, directionality, self-cleaning ability, rough surface adhesion and high adhesive stress. However, fully exploiting these adhesives in practical applications at different length scales requires efficient scaling (i.e. with little loss in adhesion as area grows). Just as natural gecko adhesives have been used as a benchmark for syn...

  18. A dislocation density based micromechanical constitutive model for Sn-Ag-Cu solder alloys

    Science.gov (United States)

    Liu, Lu; Yao, Yao; Zeng, Tao; Keer, Leon M.

    2017-10-01

    Based on the dislocation density hardening law, a micromechanical model considering the effects of precipitates is developed for Sn-Ag-Cu solder alloys. According to the microstructure of the Sn-3.0Ag-0.5Cu thin films, intermetallic compounds (IMCs) are assumed as sphere particles embedded in the polycrystalline β-Sn matrix. The mechanical behavior of polycrystalline β-Sn matrix is determined by the elastic-plastic self-consistent method. The existence of IMCs not only impedes the motion of dislocations but also increases the overall stiffness. Thus, a dislocation density based hardening law considering non-shearable precipitates is adopted locally for single β-Sn crystal, and the Mori-Tanaka scheme is applied to describe the overall viscoplastic behavior of solder alloys. The proposed model is incorporated into finite element analysis and the corresponding numerical implementation method is presented. The model can describe the mechanical behavior of Sn-3.0Ag-0.5Cu and Sn-1.0Ag-0.5Cu alloys under high strain rates at a wide range of temperatures. Furthermore, the overall Young’s modulus changes due to different contents of IMCs is predicted and compared with experimental data. Results show that the proposed model can describe both elastic and inelastic behavior of solder alloys with reasonable accuracy.

  19. [Segmental sternal dislocation in children. Apropos of a surgically treated case].

    Science.gov (United States)

    Norotte, G; Peres, E; Vanderweyen, A; Razafindralasitra, P

    1997-01-01

    The authors report one operated case of traumatic sternal segmental dislocation in a child, and propose a mechanism for this uncommon lesion. A fourteen year old boy was admitted in emergency for anterior chest pain, occurring during an exercise in parallel bars without any fall. X ray showed traumatic dislocation of the upper sternal segment. After 12 hours, because of bad clinical tolerance (pain, dyspnea with sweats and disphagia) reduction and plate stabilization (Senegas plate) was performed with immediate pain relief. The boy returned to school after 10 days. Plate was removed two months later after healing, with good clinical and radiological results. According to rare published cases, conservative treatment can be proposed in very young children because of dislocation remodeling. By others, in case of bad tolerance, surgical treatment is suggested despite the inconvenient of device's removal. The originality of this case is the indirect lesion mechanism. Hypothesis is given by authors. Treatment by plate is easy and gives immediate pain relief with good clinical and radiological results in teen-agers.

  20. Alloying effects of refractory elements in the dislocation of Ni-based single crystal superalloys

    Directory of Open Access Journals (Sweden)

    Shiyu Ma

    2016-12-01

    Full Text Available The alloying effects of W, Cr and Re in the [100] (010 edge dislocation cores (EDC of Ni-based single crystal superalloys are investigated using first-principles based on the density functional theory (DFT. The binding energy, Mulliken orbital population, density of states, charge density and radial distribution functions are discussed, respectively. It is clearly demonstrated that the addition of refractory elements improves the stability of the EDC systems. In addition, they can form tougher bonds with their nearest neighbour (NN Ni atoms, which enhance the mechanical properties of the Ni-based single crystal superalloys. Through comparative analysis, Cr-doped system has lower binding energy, and Cr atom has evident effect to improve the systemic stability. However, Re atom has the stronger alloying effect in Ni-based single crystal superalloys, much more effectively hindering dislocation motion than W and Cr atoms.

  1. Case of bilateral Galeazzi fractures associated with dislocation of the right elbow.

    Science.gov (United States)

    Nanno, Mitsuhiko; Sawaizumi, Takuya; Takai, Shinro

    2011-01-01

    We report an unusual case of bilateral Galeazzi fractures associated with dislocation of the right elbow and fracture of the right scaphoid caused by a motorbike accident in a 32-year-old man. Bilateral radiuses were fixed with plates, and the right scaphoid was fixed with a screw after closed reduction of the right elbow. A satisfactory result was obtained with a return to work and no radiographic problems 7 years after surgery. The mechanism of the injury was thought to be a high-velocity fall on the outstretched hands combined with extreme pronation of the forearms and extension of the wrists and the elbows. This case had a favorable outcome following operative stabilization of the fracture-dislocations and early mobilization.

  2. Lens dislocation has a possible relationship with laser iridotomy

    Directory of Open Access Journals (Sweden)

    Mutoh T

    2012-12-01

    Full Text Available Tetsuya Mutoh,1,2 Kevin F Barrette,2 Yukihiro Matsumoto,1 Makoto Chikuda11Department of Ophthalmology, Dokkyo Medical University Koshigaya Hospital, Koshigaya City, Saitama, Japan; 2Department of Ophthalmology, Boston University School of Medicine, Boston, MA, USAAbstract: We report our recent experience of four eyes with spontaneous lens dislocation in four patients with no history of trauma or any systemic disease associated with zonular dialysis. Lens dislocation developed with 0.5 to 6 months following laser iridotomy. All patients were male and two eyes were complicated with acute primary angle closure glaucoma preoperatively. Case 1 showed bilateral lens dislocation, while cases 2 and 3 involved unilateral lens dislocation. Cases 2 and 3 showed lenses completely dislocated into the vitreous cavity. All cases needed lens removal and scleral fixation of intraocular lenses. Final visual acuity was 1.2 in all cases. We suspect that laser iridotomy may induce localized zonular dialysis that results in progressive zonular weakness, leading to lens dislocation.Keywords: lens dislocation, laser iridotomy, primary angle closure glaucoma

  3. Study of dislocations in nanoscale semiconductors by ab initio molecular dynamics and lattice Green's function methods

    Energy Technology Data Exchange (ETDEWEB)

    Masuda-Jindo, K. [Department of Materials Science and Engineering, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan); Hung, Vu Van [Hanoi National Pedagogic University, km8 Hanoi-Sontay Highway, Hanoi (Viet Nam); Menon, M. [Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506 (United States)

    2005-04-01

    The electronic and mechanical properties of the nanoscale materials are studied by using an ab initio molecular dynamics (TBMD) method and temperature dependent lattice Green's function method. The core structures of dislocations in semiconductor crystallites composed of {proportional_to}1000 atoms are calculated using the ab initio TB molecular dynamics method and compared with those in the corresponding bulk semiconductors. The core structures of both 30 and 90 partial dislocations in Si crystallites are found to be similar to those of the bulk Si crystals, but excess energies of the dislocations are of considerably smaller in the small semiconductor crystallites. We also investigate the mechanical (dislocation) properties of carbon related nanoscale materials, graphen in comparison with CNT, by using the temperature dependent Lattice Green's function method and we will show that the thermodynamic and mechanical properties of the nanoscale materials are quite different from those of the corresponding bulk materials. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  4. Constrained liners for recurrent dislocations in total hip arthroplasty

    DEFF Research Database (Denmark)

    Knudsen, R; Ovesen, O; Kjaersgaard-Andersen, P

    2009-01-01

    This study reports the results and complications from treating recurrent hip dislocations with a constrained liner (CL) after total hip arthroplasty (THA). Forty patients who had a CL inserted as a secondary prophylactic treatment were retrospectively reviewed after a median observation period...... of 27 months (range 7-77 months). During the observation period five patients had to be revised: one for deep infection and four on account of re-dislocations. Our results indicate that patients with recurrent THA dislocations can be treated with a CL and has a satisfactory low complication rate...

  5. Galeazzi fracture with volar dislocation of the distal radioulnar joint.

    Science.gov (United States)

    Kim, Suezie; Ward, James P; Rettig, Michael E

    2012-11-01

    Galeazzi fracture dislocations are fractures of the distal one-third of the radial diaphysis with traumatic disruption of the distal radioulnar joint (DRUJ). This injury results in subluxation or dislocation of the ulnar head. We present a case of a Galeazzi fracture with a volar dislocation of the DRUJ. Open reduction of the DRUJ with Kirschner wire fixation in pronation was necessary to reduce the joint and maintain anatomic alignment. Repair of the triangular fibrocartilage complex was also necessary to maintain stability of the DRUJ.

  6. Bilateral Posterior Native Hip Dislocations after Fall from Standing

    Directory of Open Access Journals (Sweden)

    Jane Xiao

    2017-10-01

    Full Text Available We present a case of bilateral posterior native hip dislocations after a fall from standing. This exceedingly rare diagnosis is classically associated with younger patients whose bones are strong enough to dislocate rather than fracture in the setting of a high-momentum collision. We present an unusual case of an 88-year-old male with native hips who sustained a low-energy collision after falling from standing and was found to have bilateral posterior hip dislocations without associated pelvis or femur fractures.

  7. Radiological difficulty in identifying unicompartmental knee replacement dislocation

    Directory of Open Access Journals (Sweden)

    Mr Oruaro Adebayo Onibere, MBBS, MRCS

    2017-09-01

    Full Text Available Unicondylar knee replacement is a relatively common elective orthopedic procedure but is not often seen in the Emergency Department setting. Familiarity with normal clinical and radiological appearances is difficult to gain. Dislocation of the mobile bearing component “spacer” is a known complication of unicondylar knee replacements, and these patients will initially present to the accident and Emergency Department. In this setting, an accurate and prompt diagnosis is necessary to appropriately manage the patient's condition. There is normally a radiological challenge in identifying dislocated mobile bearings on plain radiographs. These patients may need to have further imaging, such as a computer tomographic scan to identify the dislocated mobile bearing.

  8. Superior dislocation of the patella: a case report

    Directory of Open Access Journals (Sweden)

    Garcia-Balletbo Montserrat

    2009-07-01

    Full Text Available Abstract Background Superior dislocation of the patella is an uncommon condition that mainly occurs in knees with a high patella and medial femorotibial degenerative arthritis. There are no previous reports of this condition occurring in association with tibial valgus osteotomy. Case report: We report the case of a patient in whom vertical dislocation recurred twice at 4 months after tibial valgus osteotomy. To avert additional recurrence or new dislocations, the patient was treated surgically to remove the existing osteophytes. Conclusions: An arthroscopic approach was decided because of the lower associated morbidity and good results with this technique compared to open surgery.

  9. Concentric reduction of the dislocated hip: computed tomographic evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Hernandez, R.J.

    1984-01-01

    Concentric reduction of a dislocated hip can be evaluated by anteroposterior views or linear tomography. Anterior relationships, however, may be difficult to evaluate from a frontal radiograph despite good visibility. Computed tomography (CT), because of its cross-sectional imaging capabilities, is superior in demonstrating these relationships. The CT appearance of two types of dislocations (posterior and lateral ) is described. A posterior dislocation should be suspected if the femoral metaphysis approximates the acetabulum, a mass projects behind the ischium, or the fat plane anterior to the gluteus maximus is deformed or displaced posteriorly.

  10. The CLIMB Geoportal - A web-based dissemination and documentation platform for hydrological modelling data

    Science.gov (United States)

    Blaschek, Michael; Gerken, Daniel; Ludwig, Ralf; Duttmann, Rainer

    2015-04-01

    Geoportals are important elements of spatial data infrastructures (SDIs) that are strongly based on GIS-related web services. These services are basically meant for distributing, documenting and visualizing (spatial) data in a standardized manner; an important but challenging task especially in large scientific projects with a high number of data suppliers and producers from various countries. This presentation focuses on introducing the free and open-source based geoportal solution developed within the research project CLIMB (Climate Induced Changes on the Hydrology of Mediterranean Basins, www.climb-fp7.eu) that serves as the central platform for interchanging project-related spatial data and information. In this collaboration, financed by the EU-FP7-framework and coordinated at the LMU Munich, 21 partner institutions from nine European and non-European countries were involved. The CLIMB Geoportal (lgi-climbsrv.geographie.uni-kiel.de) stores and provides spatially distributed data about the current state and future changes of the hydrological conditions within the seven CLIMB test sites around the Mediterranean. Hydrological modelling outcome - validated by the CLIMB partners - is offered to the public in forms of Web Map Services (WMS), whereas downloading the underlying data itself through Web Coverage Services (WCS) is possible for registered users only. A selection of common indicators such as discharge, drought index as well as uncertainty measures including their changes over time were used in different spatial resolution. Besides map information, the portal enables the graphical display of time series of selected variables calculated by the individual models applied within the CLIMB-project. The implementation of the CLIMB Geoportal is finally based on version 2.0c5 of the open source geospatial content management system GeoNode. It includes a GeoServer instance for providing the OGC-compliant web services and comes with a metadata catalog (pycsw) as well

  11. Physiological responses to simulated stair climbing in professional firefighters wearing rubber and leather boots.

    Science.gov (United States)

    Huang, Chun-Jung; Garten, Ryan S; Wade, Chip; Webb, Heather E; Acevedo, Edmund O

    2009-09-01

    No studies have considered whether a firefighter's boots are a factor influencing physiological responses. The purpose of this study was to examine physiological responses to a fire simulation activity (stair climb) in professional firefighters wearing rubber boots (RB) and leather boots (LB). Twelve professional firefighters participated in two counterbalanced simulated firefighter stair climb (SFSC) sessions, one wearing RB and the other wearing LB. Heart rate, oxygen uptake (VO(2)), expiratory ventilation (V(E)), blood lactate (BLa), salivary cortisol (SCORT), and leg strength were assessed prior to and following a SFSC. LB elicited significantly greater SCORT values and knee flexion time to peak torque. Furthermore, RB revealed significantly greater ankle dorsiflexion peak torque after SFSC. BLa was positively related to knee flexion peak torque after SFSC in the RB. Firefighters when wearing the RB may be more effective at resisting fatigue and increase more force production.

  12. Reduced Moment-Based Models for Oxygen Precipitates and Dislocation Loops in Silicon

    Science.gov (United States)

    Trzynadlowski, Bart

    The demand for ever smaller, higher-performance integrated circuits and more efficient, cost-effective solar cells continues to push the frontiers of process technology. Fabrication of silicon devices requires extremely precise control of impurities and crystallographic defects. Failure to do so not only reduces performance, efficiency, and yield, it threatens the very survival of commercial enterprises in today's fiercely competitive and price-sensitive global market. The presence of oxygen in silicon is an unavoidable consequence of the Czochralski process, which remains the most popular method for large-scale production of single-crystal silicon. Oxygen precipitates that form during thermal processing cause distortion of the surrounding silicon lattice and can lead to the formation of dislocation loops. Localized deformation caused by both of these defects introduces potential wells that trap diffusing impurities such as metal atoms, which is highly desirable if done far away from sensitive device regions. Unfortunately, dislocations also reduce the mechanical strength of silicon, which can cause wafer warpage and breakage. Engineers must negotiate this and other complex tradeoffs when designing fabrication processes. Accomplishing this in a complex, modern process involving a large number of thermal steps is impossible without the aid of computational models. In this dissertation, new models for oxygen precipitation and dislocation loop evolution are described. An oxygen model using kinetic rate equations to evolve the complete precipitate size distribution was developed first. This was then used to create a reduced model tracking only the moments of the size distribution. The moment-based model was found to run significantly faster than its full counterpart while accurately capturing the evolution of oxygen precipitates. The reduced model was fitted to experimental data and a sensitivity analysis was performed to assess the robustness of the results. Source

  13. The evolution of angiosperm lianescence without vessels--climbing mode and wood structure-function in Tasmannia cordata (Winteraceae).

    Science.gov (United States)

    Feild, Taylor S; Chatelet, David S; Balun, Lawong; Schilling, Edward E; Evans, Robert

    2012-01-01

    • The lack of extant lianescent vessel-less seed plants supports a hypothesis that liana evolution requires large-diameter xylem conduits. Here, we demonstrate an unusual example of a lianoid vessel-less angiosperm, Tasmannia cordata (Winteraceae), from New Guinea. • Wood mechanical, hydraulic and structural measurements were used to determine how T. cordata climbs and to test for ecophysiological shifts related to liana evolution vs 13 free-standing congeners. • The tracheid-based wood of T. cordata furnished low hydraulic capacity compared with that of vessel-bearing lianas. In comparison with most nonclimbing relatives, T. cordata possessed lower photosynthetic rates and leaf and stem hydraulic capacities. However, T. cordata exhibited a two- to five-fold greater wood elastic modulus than its relatives. • Tasmannia cordata provides an unusual example of angiosperm liana evolution uncoupled from xylem conduit gigantism, as well as high plasticity and cell type diversity in vascular development. Because T. cordata lacks vessels, our results suggest that a key limitation for a vessel-less liana is that strong and low hydraulically conductive wood is required to meet the mechanical demands of lianescence. © 2011 The Authors. New Phytologist © 2011 New Phytologist Trust.

  14. The Effect of Climbing as a Recreational Event on Adoles ent ’ s Locus of Control

    Directory of Open Access Journals (Sweden)

    Güçlü ÖZEN

    2014-07-01

    Full Text Available The aim of this study was to determine the effect of experience of the secondary education ( class 10th and 11th students‟ participation on artificial wall climbing refe r r ed to experiential learning education and defined as high activity on th eir locus of control . Artifical wall climbing is a learning point beyond the sport act ivity that give an opportunity to participants recognize their own limits and others and do they active not passive . This study was done as pretest - posttest control group with quasi - experimental model and the data were collected using „ Nowicki - Strickland Locus of Control Scale‟ adapted to Turkish by Yeşilyaprak (1988 . In this research, 90 students (40 female, 50 male aged 17 ,75 ±1.06 participated voluntery and divided in two groups as a trail and control group randomly. Trial group participated artifcial wall climbing twice a week, totel six weeks. During this time period the control group not join any activity has continued to normal life. As a result of the statistical analysis, no significant difference s were found between control and trial groups pre - test scores (p>0.05. No significant difference s were found between pre and post - test scores of control group (p>0.05, significant differences were found between pre and post - test scores of trial group (p0.05 and no significant differences between the difference of the differences (p>0.05. C onsequently, it could be said that the articifal wall climbing activities has a positive efect on the particip ants‟ locus of control, it caused a movement from out side to inside. And it has a significant effect on gender differences, that women have more gain than men.

  15. On Heels and Toes: How Ants Climb with Adhesive Pads and Tarsal Friction Hair Arrays.

    Directory of Open Access Journals (Sweden)

    Thomas Endlein

    Full Text Available Ants are able to climb effortlessly on vertical and inverted smooth surfaces. When climbing, their feet touch the substrate not only with their pretarsal adhesive pads but also with dense arrays of fine hairs on the ventral side of the 3rd and 4th tarsal segments. To understand what role these different attachment structures play during locomotion, we analysed leg kinematics and recorded single-leg ground reaction forces in Weaver ants (Oecophylla smaragdina climbing vertically on a smooth glass substrate. We found that the ants engaged different attachment structures depending on whether their feet were above or below their Centre of Mass (CoM. Legs above the CoM pulled and engaged the arolia ('toes', whereas legs below the CoM pushed with the 3rd and 4th tarsomeres ('heels' in surface contact. Legs above the CoM carried a significantly larger proportion of the body weight than legs below the CoM. Force measurements on individual ant tarsi showed that friction increased with normal load as a result of the bending and increasing side contact of the tarsal hairs. On a rough sandpaper substrate, the tarsal hairs generated higher friction forces in the pushing than in the pulling direction, whereas the reverse effect was found on the smooth substrate. When the tarsal hairs were pushed, buckling was observed for forces exceeding the shear forces found in climbing ants. Adhesion forces were small but not negligible, and higher on the smooth substrate. Our results indicate that the dense tarsal hair arrays produce friction forces when pressed against the substrate, and help the ants to push outwards during horizontal and vertical walking.

  16. On Heels and Toes: How Ants Climb with Adhesive Pads and Tarsal Friction Hair Arrays.

    Science.gov (United States)

    Endlein, Thomas; Federle, Walter

    2015-01-01

    Ants are able to climb effortlessly on vertical and inverted smooth surfaces. When climbing, their feet touch the substrate not only with their pretarsal adhesive pads but also with dense arrays of fine hairs on the ventral side of the 3rd and 4th tarsal segments. To understand what role these different attachment structures play during locomotion, we analysed leg kinematics and recorded single-leg ground reaction forces in Weaver ants (Oecophylla smaragdina) climbing vertically on a smooth glass substrate. We found that the ants engaged different attachment structures depending on whether their feet were above or below their Centre of Mass (CoM). Legs above the CoM pulled and engaged the arolia ('toes'), whereas legs below the CoM pushed with the 3rd and 4th tarsomeres ('heels') in surface contact. Legs above the CoM carried a significantly larger proportion of the body weight than legs below the CoM. Force measurements on individual ant tarsi showed that friction increased with normal load as a result of the bending and increasing side contact of the tarsal hairs. On a rough sandpaper substrate, the tarsal hairs generated higher friction forces in the pushing than in the pulling direction, whereas the reverse effect was found on the smooth substrate. When the tarsal hairs were pushed, buckling was observed for forces exceeding the shear forces found in climbing ants. Adhesion forces were small but not negligible, and higher on the smooth substrate. Our results indicate that the dense tarsal hair arrays produce friction forces when pressed against the substrate, and help the ants to push outwards during horizontal and vertical walking.

  17. Musical stairs: the impact of audio feedback during stair-climbing physical therapies for children.

    Science.gov (United States)

    Khan, Ajmal; Biddiss, Elaine

    2015-05-01

    Enhanced biofeedback during rehabilitation therapies has the potential to provide a therapeutic environment optimally designed for neuroplasticity. This study investigates the impact of audio feedback on the achievement of a targeted therapeutic goal, namely, use of reciprocal steps. Stair-climbing therapy sessions conducted with and without audio feedback were compared in a randomized AB/BA cross-over study design. Seventeen children, aged 4-7 years, with various diagnoses participated. Reports from the participants, therapists, and a blinded observer were collected to evaluate achievement of the therapeutic goal, motivation and enjoyment during the therapy sessions. Audio feedback resulted in a 5.7% increase (p = 0.007) in reciprocal steps. Levels of participant enjoyment increased significantly (p = 0.031) and motivation was reported by child participants and therapists to be greater when audio feedback was provided. These positive results indicate that audio feedback may influence the achievement of therapeutic goals and promote enjoyment and motivation in young patients engaged in rehabilitation therapies. This study lays the groundwork for future research to determine the long term effects of audio feedback on functional outcomes of therapy. Stair-climbing is an important mobility skill for promoting independence and activities of daily life and is a key component of rehabilitation therapies for physically disabled children. Provision of audio feedback during stair-climbing therapies for young children may increase their achievement of a targeted therapeutic goal (i.e., use of reciprocal steps). Children's motivation and enjoyment of the stair-climbing therapy was enhanced when audio feedback was provided.

  18. STS-38 MS Springer climbs through CCT side hatch prior to egress training

    Science.gov (United States)

    1990-01-01

    STS-38 Mission Specialist (MS) Robert C. Springer, wearing launch and entry suit (LES), climbs through the side hatch of the crew compartment trainer (CCT) located in JSC's Mockup and Integration Laboratory (MAIL) Bldg 9A. Springer will practice emergency egress through the side hatch using the crew escape system (CES) pole (at Springer's left). The inflated safety cushion under Springer will break his fall as he rolls out of the side hatch.

  19. Non-destructive testing and condition monitoring with mobile wall climbing and swimming robots

    OpenAIRE

    Sattar, T

    2014-01-01

    Reliable Non Destructive Testing (NDT) is vital to the integrity, performance management and sustainability of capital assets in safety critical industries such as oil and gas, aerospace, transportation, power generation and off-shore and subsea operations. The talk will explore opportunities to improve the NDT of industrial structures and decrease the cost of inspection by automating the NDT with mobile robots. The challenges of developing mobile wall climbing and submersible robots will be ...

  20. Burnout in climbing film two phase flow a review of theories of the mechanism

    International Nuclear Information System (INIS)

    Kirby, G.J.

    1966-03-01

    Burnout data for annular flow are examined and it is shown that for qualities above (say) 10% the burnout heat flux is a function only of pressure, D 1/2 G and quality to within the errors in the experimental data. The various burnout models are examined and none are found to predict the trends given by the above function. The literature on droplet deposition, entrainment and onset of annular flow is studied to see if any new light can be thrown on the problem of burnout. Actual values for the deposition rate of droplets in a boiling channel are derived and it is hoped that these will provide a basis for further studies of possible burnout models. (author)