Step Deformation Research Articles

Step deformation of solid amorphous polymers

The variation of step deformation kinetics in solids is studied as a function of morphological factors. Oscillations of creep rate at micrometer increments of the amount of deformation, which reflect the step nature of the process, are investigated from an interferogram. It is shown that the plasticization of polymethyl methacrylate by dibutyl phthalate blurs the steps, while their height varies insignificantly. The results are explained using the concept of the netlike structure of amorphous polymers. The data obtained confirm the universal nature of jumps as a mode of evolution of deformation in various solids. The jumps reflect the cooperative nature of motion of kinetic units, and the regular variation of the characteristics of the jumps lends support to the definition of creep as a process of structural self-organization.

潤滑圧縮法を用いた高分子溶融体の平面伸長粘度および平面伸長応力緩和測定

A technique to measure planar elongational viscosity and step-planar stress relaxation, by using a lubricated squeeze flow method with PS and LDPE, has been optimized and established. The effect of experimental conditions, i.e., the viscosity of silicone oil as a lubricant, appeared in the measurement of the planar elongational viscosity. The dependence of the uniform planar deformation behavior on the silicone oil viscosity was greater in LDPE than in PS. A high viscosity silicone oil (3.0×102Pa-s) was chosen to minimize the loss of lubricant. Although the step-planar stress relaxation experiments required speeds that exceeded the testing machine specification to achieve the step deformation, this problem was successfully solved by inserting a metal spacer between the lower plate and the sample. The high viscosity silicone oil produced uniform deformation in both materials with minimal loss of the lubricant, however, the high viscosity of the silicone oil was believed to lead larger measured G0(t) results than the predicted values. The silicone oil viscosity was optimized at a lower value of 1.0×101Pa-s which minimized the influence of the silicone oil on the results while still producing substantial lubricity. The measurement of planar elongational viscosity by using this optimal silicone oil showed strain-hardening in both samples, with LDPE showing a stronger dependence. “Time-strain separability” within a certain time period was confirmed for the step planar stress relaxation modulus under the optimized conditions.

Numerical Simulation of Extrudate Swell Problem and Evaluation of Applicability of Viscoelastic Constitutive Models. 1. A Study on Axisymmetric Extrudate Swell from a Straight Die.

Numerical simulations of axisymmetric extrudate swell for a low density polyethyrene (LDPE IUPAC-A) melt were carried out using the K-BKZ model as an integral type and the PTT and Larson models as a differential type. We employed both the reversible and irreversible models for the K-BKZ and Larson models to investigate the effect of reversing deformation on the extrudate swell from a straight die. First, relaxation spectrum and nonlinear parameters in the constitutive equation were determined from dynamic data of linear viscoelasticity and steady shear flow data by using the nonlinear regression, and then they were applied to the simulation of extrudate swell problem. We evaluated the applicability of these models by comparing experiments and simulation for both rheological data and extrudate swell ratio. For the K-BKZ model, the reversible model over-estimates the swell ratio in high shear rate, whereas the irreversible model predicts the experimental data with high accuracy. The irreversible Larson model also shows the good prediction of swell, on the other hand, the reversible one over-estimates the swell and there exists the multiple solutions. For the PTT model, we carried out the simulation using the models with different values of nonlinear parameter, e , which has the same steady shear flow properties and the different properties of stress relaxation under reversing double step deformation. The model having the larger stress in the stress relaxation under reversing double step deformation shows the larger swell. From these results, we find that the consideration of reversing deformation characteristics is required for the extrudate swell from the straight die.

On the imaging mechanism of monatomic steps in graphite

The shape and the atomic arrangement of monolayer steps of graphite have been characterized by STM. The origin of the appearance of the imaged features along the steps is discussed, addressing for the first time both morphological and electronic considerations. Extended Huckel theoretical calculations of nanotubes are used to identify the contribution of the electronic structure to the STM image of monolayer steps. We show that mechanical tip–sample interactions dominate the imaging process of graphite, leading to step deformation during scanning and negative STM contrast of the atom positions in the hexagonal unit cell.

Bilateral atraumatic dislocation of the shoulder.

A 69 year old woman was referred to the fracture clinic with a diagnosis of anterior dislocation of left shoulder. There was no history of acute injury. The patient had...

Harmonically-Interacting Step Approach to the Relaxation Process of Vicinal Surface. II. The Relaxation Process Induced by the Step-Edge Diffusion

The relaxation processes of vicinal surface induced by the diffusion of adatoms along the step edge are analyzed by the Ginzburg-Landau-Langevin equation based on the harmonically-interacting step (HIS) picture. By the equation, the time evolutions of the step deformation width and the step fluctuation width are analyzed. For the relaxation process induced by the infinite-length step-edge diffusion, these quantities show the “universal” scaling behaviors. However, both of the universality and the scaling behavior disappear for the finite-length diffusion. To verify the results quantitatively , we performed the Monte-Carlo calculations for the solid-on-solid step terrace-step-kink model. The results from the Monte-Carlo calculations agree with the analytic results from the HIS picture very well.

Harmonically-Interacting Step Approach to the Relaxation Process of Vicinal Surface. I. The Relaxation Process Induced by the Attachment-Detachment Mechanism

The relaxation process of the vicinal surface induced by the attachment-detachment mechanism is analyzed by the Ginzburg-Landau-Langevin equation based on the harmonically-interacting step (HIS) picture. By the equation, the time evolution of the step deformation width, the step fluctuation width and the step diffusion length is analyzed. For the relaxation process from small-fluctuation structure such as the ground-state structure, these quantities show the “universal” scaling behaviors. To verify the result, we performed the Monte-Carlo calculations for the free-Fermion terrace-step-kink (TSK) model and the solid-on-solid step TSK model. The result from the Monte-Carlo calculations agrees with the analytic result from the HIS picture quantitatively . For the relaxation process from the rough-surface structure, the “non-universal” scaling behaviors are obtained from the HIS analysis.

Archaeological investigation by geotomography: structure of the foundation of Yingxian timber pagoda

It is significant to take a non-destructive inspection, one of advanced techniques, for detecting the internal structure and the present status of ancient cultural relics. The results detected by geotomography in Yingxian timber pagoda, Shanxi Province, are presented in this paper. The embankment in the stepped foundation shows a three circular structure in horizontal: the circular platform core is hard, homogenous and unharmed, out of which there are some radial collapsed grooves. The middle circle with a thickness of 2 to 4 m is a compacted layer and its loading capacity decreases then. The outer protective layer has a larger porosity and a weak loading capacity. An abnormal body is found out in the core, which has a circular shape and a reverse high-absorption coefficient in the shallow part, but appears a long-band shape and a low-absorption coefficient in the deep part. It might be a disturbance caused by artificial activities: the shallow part is probably a channel filled with loosen soil and the deep part is a hidden cave. It is found that the foundation of the courtyard is homogenous and integrated. Two soft and weakened areas in the north are related to the long-term run-off and drainage of groundwater. The inclination of the timber pagoda to the northwest and northeast relates to several factors, such as the inherited subsidence of the northern foundation, the lower loading capacity of the outer stepped foundation, seismic activity and timber deformation.

Harmonically-Interacting Step Picture of the Vicinal Surface

A new coarse-grained terrace-step-kink (TSK) picture for the vicinal surface is proposed. In this picture called harmonically-interacting step (HIS) picture, the vicinal surface is expressed by an assembly of the harmonically-interacting steps which look like flexible continuous strings. Through the transfer matrix representation, we show the equivalence between the HIS picture and the capillary wave picture for the vicinal surface in the length-scale much larger than the average step-spacing. To establish the validity and to show the usefulness of the HIS picture, we pay attention to the step deformation width. The deformation width is studied both by the analytic calculation based on the HIS picture and by the Monte-Carlo calculations for the free-Fermion TSK model and for the solid-on-solid step TSK model. The results from these calculations agree very well.

Recent developments in modeling the hot working behavior of metallic materials

Three distinct trends in the modeling of hot working behavior of metallic materials are identified. These are respectively (a) analytical and numerical methods to characterize the material flow behavior and related macroscopic properties, (b) metallurgical models to predict microstructural parameters at each step in a multi-step processing operation, and (c) hot workability models to predict optimum conditions of temperature and strain rate for a single step deformation. Important features of the models are critically examined and some possible directions for future work indicated.

X-ray film measurements for healed distal radius fractures

In order to understand the effect of malunion on functional outcome, it is essential that deformity be measured in a consistent manner. A standardized method of measuring eight anatomic parameters at the distal radius was developed. By this method, six x-ray films of healed distal radius fractures were subsequently measured by 16 raters. Rater agreement was quantified by using the intraclass correlation coefficient. Tolerance limits were developed in order to estimate the expected margin of error for each parameter. Parameters measured with high rater agreement include ulnar variance, palmar tilt, and radial shift; however, even experienced clinicians did not readily agree on the size of step and gap deformity. Using the method of tolerance limits, one would expect that two randomly chosen clinicians measuring step and gap deformity on a random x-ray film will differ by more than 3 mm at least 10% of the time. Similarly, repeat step or gap measurements by the same observer are expected to differ by more than 2 mm at least 10% of the time. In view of our inability to measure deformity more accurately, the concept of a specific relationship between a given degree of deformity and outcome must be questioned. Prospective research is needed in order to improve our understanding of the precise relationship between malunion and functional outcome.

The nonlinear viscoelastic response and apparent rejuvenation of an epoxy glass

Following a quench from above the glass transition temperature Tg to below, it is known that the mechanical response evolves (physical aging) and can be represented by a time‐aging time superposition principle. The value of the aging time shift factor ate is known to depend on the magnitude of the applied stress or strain. Here the viscoelastic response of a material undergoing physical aging and subjected to a single large strain ‘‘probe’’ (step deformation followed by a step to zero deformation) followed by small strain probes is analyzed. It was found that a Bernstein, Kearsley, and Zapas (BKZ) constitutive equation which includes an aging clock that depends upon the deformation magnitude describes the response. The results are discussed and related to the apparent ‘‘rejuvenation’’ described by Struik in similar thermomechanical histories.

ABC of Sports Medicine: Management of the Acutely Injured Joint

Far too often treatment of injuries to major joints starts without a diagnosis being made. In acute joint injury it may not always be possible to get a good history — for example, when a scrum has collapsed. In many cases, however, the story points to the eventual diagnosis. A fall on the point of the shoulder damages the acromioclavicular or sternoclavicular joint; a rugby tackle that knocks the leading arm into external rotation while abducted 90° indicates a shoulder dislocation; the non-contact twisting deceleration injury of the knee followed by a snapping or popping sensation and rapid swelling is usually associated with a torn anterior cruciate. So a history really is important and is well worth the time spent before the physical examination. Short examination examination Look at the joint — Appreciable swelling will be apparent immediately, and deformity (such as patella dislocation) should not be missed. The step deformity of subluxed or dislocated acromioclavicular joints should be obvious, as would be the more subtle sharpening of the point of the shoulder when that joint is dislocated. Feel the joint — The first thing to feel for is the tenderness, which is the marker of localised injury. Look at patients' faces for apprehension when you first touch them, because once you have hurt them you are going to lose their cooperation. It is essential to feel the landmark points around a particular joint. Using the ankle as an example, gentle but specific palpation over the swollen lateral structures will differentiate the tenderness of the fibula itself if it is fractured from the tenderness overlying the anterior component of the lateral ligament, which runs almost horizontally forward from the tip of the fibula and is far more often injured. In the knee it is important to remember that the lower …

Ｅｓｔｌａｎｄｅｒ法術後の３個の三角弁を用いた口角形成法

A number of methods have been reported for reconstruction of defects after the excision of malignant tumors on the lower lip. Special interest has centered on Estlander's method, which makes triangular flaps of entire layers. The operative method is applied on a lateral part of the upper lip with a pedicle located on the median side, followed by downward transposition. The procedure can safely and easily reconstruct deficiencies in the lower lip with outstanding results. However, it requires a secondary commissuroplasty because the commissure on the affected side becomes smaller and round in shape.Several methods have been suggested for secondary commissuroplasty, but even with one of these methods, it is very difficult to create a satisfactory commissure in terms of aesthetic and functional considerations. As a new method for secondary operation, we performed the commissuroplasty with satisfactory results by forming two opposing triangular mucosal flaps in the vermilion area and a small triangular skin flap on the commissure. This method produces extremly good results, obtaining favorable commissure form and reconstruction of the mucosa of both upper lip and lower lips without an unnatural-looking color change in the mucosa or a step deformity in the vermilion.Our method could improve the results of Estlander's operations after tumor resection in the lower lip.

Local and global universal relations for first-gradient materials

Local universal relations are relations between stress and kinematic variables which hold for all materials of a particular class irrespective of specific material parameters. A method is developed for obtaining local universal relations for most first gradient materials. The currently known local universal relations for isotropic elastic materials have been extended to all isotropic first gradient materials under constant step deformation histories and have also been extended to all isotropic first gradient materials undergoing arbitrary time dependent triaxial extensions along fixed material directions. It has been shown that universal relations exist for some anisotropic materials. A set of pseudo-universal relations has been obtained for anisotropic elastic materials which can be used to decouple the material functions. These pseudo-universal relations contain some, but not all, material functions. A global universal relation has been developed for the extension and torsion of an isotropic cylindrical shaft which holds for all incompressible first gradient materials.

The treatment of duplication thumbs in children. About a series of 32 patients.

29 children with 32 duplicated thumbs were followed up. Wassel's classification was used: type I (3 cases), type II (8 cases), type IV (16 cases), type V (3 cases), type VII (2 cases). There were no type III or VI cases. Seven cases were not operated on (minor abnormalities, refusal by the parents). Simple surgical ablation was performed in 12 cases, ablation with reconstruction in 10 cases, ablation with pollicisation in one case, ablation with longitudinal osteotomy in one case. Finally, Bilhaut's technique was performed in one case. 16 cases had a good result, 9 cases were disappointing with one case of stiffness, one step deformity, one protrusion of the metacarpal head and particularly 6 cases with joint instability. This latter complication is the most frequently encountered in various series and the authors emphasize the surgical precautions to avoid its occurrence.

Er 2RhSi 3 and R 2CoGa 3 (R  Y, Tb, Dy, Ho, Er, Tm, Yb) with Lu 2CoGa 3 type structure: new members of the A1B 2 structure family

The structure of Er 2RhSi 3 was redetermined by X-ray single-crystal diffraction ( λ(Mo Kα)=0.71073 A ̊ , μ=42.392 mm −1, F(000)=892, T=293 K, R=0.037, wR=0.030 for 244 contributing unique reflections). It is shown that this silicide has a hexagonal structure of the Lu 2CoGa 3 type, hP24, (194) P6 3/ mmc-khfb, a=8.1130(7), c=7.7556(9) A ̊ , V=442.09(9) A ̊ 3, Z=4, M r=521.68, D x=7.838 mg mm −3 . The structure of isotypic Er 2 Co 1.4Ga 2.6 ( hP24, (194) P6 3/ mmc-khfb, a=8.607(3), c=6.898(3) A ̊ , V=442.5(4) A ̊ 3, Z=4, M r=598.30, D x=8.980 mg mm −3 ) was refined by X-ray powder diffraction ( λ(Fe Kα)=1.93735 A ̊ , F(000)=1017.6, T=293 K, R=0.092 for 61 reflections). The cell parameters of R 2CO 1+xGa 3−x phases (R  Y, Tb, Dy, Ho, Er, Tm, Yb; x= ±0.4) with the same structure type were obtained from X-ray powder diagrams. The Lu 2CoGa 3 structure is a distorted substitution variant of the A1B 2 type, where the trigonal Lu 6 prisms centred by cobalt atoms share triangular faces in infinite columns. The cobalt atoms are displaced away from the prism centres like the mercury atoms in the orthorhombic KHg 2 structure type. The distortions in Er 2RhSi 3 are of a lesser magnitude than those observed in Lu 2CoGa 3. A progressive substitution of gallium by cobalt along the RGa 2-RCoGa cross-sections of the R-Co-Ga systems (R  Y, Tb, Dy, Ho, Er, Tm, Yb, Lu) leads to a step by step deformation of the trigonal prisms. The main features of other deformation and substitution derivatives of the A1B 2 type are discussed.

The morphological basis of intracellular measurements in the cockroach tactile spine neuron

The femoral tactile spine of the cockroach (Periplaneta americana) contains a single sensory neuron, which adapts rapidly and completely to step deformations of the spine. Techniques for stable intracellular recording from the tactile spine neuron have recently been established, allowing electrophysiological investigation of mechanotransduction and adaptation in this sensory neuron. However, intracellular recordings from the neuron produce a wide range of action potential heights and thresholds, raising the possibility that some penetrations are in adjacent, but closely coupled supporting glial cells. This problem is exacerbated because the cell cannot be visualized during penetration. Systematic measurements of action potential heights and thresholds were made in tactile spine cells, together with identification of some penetrated cells by intracellular injection of Lucifer Yellow. All stained cells were clearly sensory neurons, although their action potential amplitudes varied from 9 mV to 80 mV. Smaller action potentials were broader than larger action potentials, and the changes in height and shape could be explained by a simple cable conduction model using measured morphological and electrical parameters. The model could also account for the observed relationship between action potential height and threshold. These results indicate that reliable recording from the tactile spine neuron is possible, but that variability in the positions of the penetration or the spike initiating zone cause an apparently wide range of electrophysiological measurements.

Practical Applications of Nasal Asymmetries in Rhinoplasty

Comparing the bones that make up each side of the nose by anthropometry reveals asymmetries caused by both developmental and traumatic processes, which precludes performing osteotomies using a set procedure. The frontal process of the maxilla is a key structure in narrowing the bony contours of the nose to correct the “open roof syndrome” (incomplete closure of the roof of the nose) after hump removal. It must be included in many instances in order to achieve a satisfactory infracture. This is especially important in the management of a large or asymmetric frontal process. Furthermore, osteotomies should be placed sufficiently lateral to the nasal bones to prevent the aesthetically unpleasing complication of the so-called step deformity. The questionable efficacy of osteotomies in rhinoplasty on the non-Caucasian nose is also briefly considered in this article.

Hardening due to pre-existing ϵ-Martensite in an Fe-30Mn-1Si alloy single crystal

Plastic flol of an Fe-30Mn-1Si alloy single crystal has been examined belol and above the Md temperature. By conducting a tlo step deformation test, it has been found that pre-injected ϵ-plates produce extremely large resistance against motion of either perfect or partial dislocations crossing them, in contrast to the relatively small hardening observed in the identical test of an Fe-18Cr-14Ni alloy. This has been discussed in terms of the dislocation pile-up and the resistance to plastic deformation in the blocking ϵ plates. Collision to and penetration through pre-injected ϵ plates of a groling ϵ plate have been examined under an electron microscope.