Asymmetric Curvature Research Articles

Research on point pressing process of curved parts of thick plates with asymmetric double curvature of high strength steel

Abstract High-strength steel asymmetric double-curvature thick plate curved parts are widely used in shipbuilding, nuclear power and other industries, but their accurate forming has been a challenge due to their high strength, large size, asymmetric structure and serious springback. In this paper, the simulation analysis study of spot press forming is carried out with large-size double-curvature spherical thick shells as the research object, and the effects of mould surface size, mould radius of curvature on the results of pressing and forming of asymmetric double-curvature curved thick plate parts made of high-strength steel are analyzed. The results show that the pressing route of pressing the centre of the slab first and then carrying out point pressing along the line of symmetry to the surroundings has the best forming effect. Different mould profile dimensions and radius of curvature of the profile have a great influence on the simulated forming results.

Evaluating controls on deformation patterns and styles in the salt-detached Sureste Basin, southern gulf of Mexico: Insights from physical models

The Sureste Basin forms the southern portion of the Isthmian Salt Province in the southern Gulf of Mexico. This basin is unique in this region as it is both part of a passive/divergent margin and also part of an active/convergent margin due to its proximity to Pacific margin plate tectonics. As a result it has experienced both orogenic and gravity-driven deformation resulting in a complex array of deformation styles and patterns. Our goal is to understand some of the structural patterns and impact of various driving forces in this basin using a series of regional-scale physical models. In particular the Sureste Basin illustrates five major complexities that we explore using our models.1) Sureste narrows from south to north — models with a trapezoidal shape illustrate heightened complexities on their margins where constrictional strains associated with convergent basin margins form transpressional systems.2) Entire basin has been shortened — unlike typical salt detached gravity-driven deformation where shortening is focused at the downdip margin of the salt basin, a combination of a gravity driven and tectonically induced shortening in our models produces shortening structures spanning the entire basin.3) Sureste is full of diapirs and allochthonous salt bodies — the presence of a major diapir network coupled with gravity-driven and moving-endwall induced shortening rejuvenates diapirs all the way to the distal pinchout, with diapir linkage forming complex, composite, curvilinear fold and thrust structures encompassing the basin.4) Sureste has been affected by non-parallel driving forces — in models where the shortening direction is 45° oblique to the regional dip direction this results in major transpression against the western margin of the basin, and initial transtension on the eastern margin as the salt flows down this regional dip. Structures display an asymmetric curvature in structural grain from east to west due to these non-parallel driving forces. Introducing thicker model salt and a multi-stage history to our model formed major diapir and canopy systems, a variety of thrust welds, roho extension down the regional dipslope, as well as major structural curvature, partly matching gross structural patterns seen in Sureste, and.5) Variable salt isopach in Sureste — in our final model the salt isopach thinned across the basin towards the East. The presence of this variable salt isopach controlled where major canopies and isolated salt bodies formed in the basin with these locations being a close match to those seen in Sureste.

Asymmetric Curvature Side-Polished Optical Fiber Coupler

Asymmetric Curvature Side-Polished Optical Fiber Coupler

A rare case of 9years congenital muscular torticollis treated with complete unipolar sternocleidomastoid release: A case report and literature review.

IntroductionCongenital muscular torticollis (CMT), when left untreated, may result in numerous complications such as eye movement disorder, craniofacial asymmetry, neck pain and compensatory asymmetrical spine curvature that worsens with age. We reported a 9-year-old boy with neglected CMT treated with complete unipolar sternocleidomastoid release.Presentation of caseA 9-year-old boy presented with his head tilted to the left since he was born. Physical examination revealed tense and uptight sternocleidomastoid muscle. The patient then underwent complete unipolar stenocleidomastoid release. Postoperatively, the patient completed 3 months of aggressive physical therapy thrice a week followed by a home exercise regimen once the patient was discharged from therapy. At six months of follow-up, the active range of motion of his neck was markedly improved in all directions, and his cervical spine was noted to be straight. The CMA was also decreased from 14 to 0 degree.DiscussionIt is recommended that, in those with CMT, the surgery should be performed between 1 and 4 years of age. However, in our case, the patient was already 9 years old. Nevertheless, he had achieved regained full cervical range of motion, and significant improvement of CMA angle (from 14 to 0 degree postoperatively) after undergoing unipolar sternocleidomastoid release and three months of aggressive physical therapy.ConclusionSurgical intervention followed by aggressive physical therapy for patients with neglected CMT, despite late presentation, may still carry a favourable outcome.

Tuning surface curvatures and young's moduli of TPMS-based lattices independent of volume fraction

Scaffold surface curvature is crucial to guide cell growth and form tissues, and the Young’s modulus of an implant should match the tissue in the implant site. Usually, the curvature and modulus are coupled with volume fraction. Inspired by the lattice slip phenomenon, we propose two structural design methods, linear slip transformation (LST) and rotational slip transformation (RST), to distort an original structure for largely tuning its curvature distribution and Young’s modulus within the restrictions of fixed structural type, volume fraction, and fabricated material. Here samples were additively manufactured using Ti6Al4V. Compared to original triply periodic minimal surfaces (TPMS) based lattices, the curvature distribution spectrum was largely broadened, and negative curvatures were introduced by both LST (generating symmetrical curvature distribution) and RST (generating asymmetrical curvature distribution). Additionally, LST and RST can continuously adjust the Young’s modulus of the original lattice and obtain a drop up to 90 % with 0.3 vol fraction, which can be expected to match soft trabecular bones. Interestingly, the resulting structures show elastic anisotropy and slip-induced deformation. The proposed approaches can be applied to biomedical applications and used to adjust lattice properties for use in energy, aerospace, and optics.

Single-minded 2 is required for left-right asymmetric stomach morphogenesis.

The morphogenesis of left-right (LR) asymmetry is a crucial phase of organogenesis. In the digestive tract, the development of anatomical asymmetry is first evident in the leftward curvature of the stomach. To elucidate the molecular events that shape this archetypal laterality, we performed transcriptome analyses of the left versus right sides of the developing stomach in frog embryos. Besides the known LR gene pitx2, the only gene found to be expressed asymmetrically throughout all stages of curvature was single-minded 2 (sim2), a Down Syndrome-related transcription factor and homolog of a Drosophila gene (sim) required for LR asymmetric looping of the fly gut. We demonstrate that sim2 functions downstream of LR patterning cues to regulate key cellular properties and behaviors in the left stomach epithelium that drive asymmetric curvature. Our results reveal unexpected convergent cooption of single-minded genes during the evolution of LR asymmetric morphogenesis, and have implications for dose-dependent roles of laterality factors in non-laterality-related birth defects.

Vernal keratoconjunctivitis and keratoconus.

Vernal keratoconjunctivitis (VKC) is a severe allergic inflammatory disease affecting the conjunctiva in children and young adults. Keratoconus (KC) is a progressive corneal disease characterized by thinning of the corneal stroma, increased and asymmetric corneal curvature, with a potential for significant visual deterioration and is one of the most common corneal complications of VKC. We aimed to review the association of these two diseases, with focus on the mechanisms, prevalence, natural history and treatment strategies of KC associated with VKC. KC is a common complication of VKC. KC prevalence can be as high as 26.8% among VKC patients, whereas abnormal corneal topography may appear in up to 71% of them. It is more severe and progresses faster in the setting of VKC (P < 0.05), with remarkable visual deterioration and with an increased need for keratoplasty. Crosslinking treatment and corneal transplantation appear to be as effective for KC patients with VKC as compared to the patients without VKC. However, postoperative complications are higher in patients with VKC and demand close monitoring, tight control of local inflammation and prompt awareness with consequent restrain of eye rubbing. Patients with VKC should be closely monitored for KC. Prompt recognition of VKC and KC allows tight control of KC pathogenesis mechanisms, timely management of KC progression and preservation of vision and quality of life of young patients.

Sharply Angled Lateral Curvature Modification in Anal Fin of a Viviparous Fish, Xenotoca variata (Cyprinodontiformes: Goodeidae).

Almost all viviparous species possess male external genitalia; for example, the mammalian penis is an intromittent organ. Some live-bearing bony fish use their anal fins to assist in mating and internal fertilization. We previously reported a male-specific asymmetric curvature at the posterior end of the anal fin in Xenotoca eiseni, a viviparous fish of the family Goodeidae. However, three other goodeid species, Xenotoca melanosoma, Zoogoneticus quitzeoensis, and Chapalichthys pardalis, examined in that study possessed lesser anal fin curvature modifications as compared to those in the anal fin of X. eiseni. Here, we report the second case of acute-angled curvature modification of the male anal fin in the family Goodeidae. We obtained a dead specimen of the goodeid species Xenotoca variata from a city zoo in Japan, and the morphological and histological analyses indicated an acute-angled asymmetric curvature of the posterior end of the anal fin in X. variata, similar to that observed in X. eiseni in the previous study. However, in our previous report, obtuse-angled modification was only observed in one other Xenotoca species, X. melanosoma, and two species belonging to other genera, Z. quitzeoensis and C. pardalis. Therefore, our findings suggest that the acute-angled curvature in the male anal fin has been developed in the genus Xenotoca.

Abrupt degenerately-doped silicon nanowire tunnel junctions

We have confirmed the presence of narrow, degenerately-doped axial silicon nanowire (SiNW) p-n junctions via off-axis electron holography (EH). SiNWs were grown via the vapor-solid-liquid (VLS) mechanism using gold (Au) as the catalyst, silane (SiH4), diborane (B2H6) and phosphine (PH3) as the precursors, and hydrochloric acid (HCl) to stabilize the growth. Two types of growth were carried out, and in each case we explored growth with both n/p and p/n sequences. In the first type, we abruptly switched the dopant precursors at the desired junction location, and in the second type we slowed the growth rate at the junction to allow the dopants to readily leave the Au catalyst. We demonstrate degenerately-doped p/n and n/p nanowire segments with abrupt potential profiles of 1.02 ± 0.02 and 0.86 ± 0.3 V, and depletion region widths as narrow as 10 ± 1 nm via EH. Low temperature current-voltage measurements show an asymmetric curvature in the forward direction that resemble planar gold-doped tunnel junctions, where the tunneling current is hidden by a large excess current. The results presented herein show that the direct VLS growth of degenerately-doped axial SiNW p-n junctions is feasible, an essential step in the fabrication of more complex SiNW-based devices for electronics and solar energy.

Dynamics of single droplet impact on cylindrically-curved superheated surfaces

Liquid droplet impact on superheated symmetric surfaces such as flat and spherical geometries has been extensively investigated in the past. However, the effect of a superheated asymmetric curvature on the collision dynamics remains unknown. In this study, experiments are performed to elucidate the thermo-hydrodynamic behavior of milli-metric water droplets impacting on superheated cylindrical surfaces having convex and concave profiles. These geometries offer an asymmetric zone for droplets to expand and retract. Mono-dispersed water droplets are impinged on convex and concave surfaces maintained in the temperature range of 125–290 °C. The impact Weber number is varied between 5 and 65 and droplet evolution is visualized using the high-speed imaging technique. It is observed that, droplet morphology and spreading characteristics are entirely different for convex and concave surfaces compared to a flat substrate due to momentum anisotropy. The maximum spread factor and residence time of the water droplet are significantly influenced by the impact Weber number while the surface superheat has negligible effect. Importantly, the asymmetric distribution of momentum facilitated 16% and 24% reduction in contact time for convex and concave surfaces respectively. The preferential extension of fluid in the azimuthal direction assisted by the gravity causes greater spreading of droplets on a convex surface. In contrary, these conditions enforced a reduction in contact time for droplets on a concave topography.

Mechanical mechanisms of the directional shift and inverse of the eccentric compound droplet

Mechanical mechanisms of the directional movement and inverse of an eccentric compound droplet in a modest extensional flow are investigated in this paper by spectral boundary element methods. In this work, a phenomenon is revealed that the shift of a compound droplet is driven by the asymmetric interfacial curvature, not just the outer drag. The asymmetric layout of the daughter droplet leads to the asymmetric drags from the continuous phase and the asymmetric deformation of the compound droplet with different interface curvatures. As the inner droplet has both enhancing and suppressing effects on the globule deformation (during different stages), the interface curvatures will vary when the relative size and location of the inner droplet are changed. The curvature difference results in the asymmetric pressure distribution and circulation inside the compound droplet. Eventually, the interaction of the inner driving force (curvature difference) and the outer drags results in the directional shift and inverse of the compound droplet. The shift direction is affected by the structural asymmetry parameter ε (eccentricity) and some flow features such as the capillary number. The conclusion could enlighten potential applications for the movement of soft globules driven by the curvature difference.

Study on asymmetrical deformation and curvature of heavy cylinder rolling

In this work, an analytical model based on slab method is proposed to calculate the force parameters in asymmetrical heavy cylinder rolling where the rolls radii, speeds, friction and contact arc lengths are different, moreover, an analytical bending curvature model to calculate the curvature at the exit of deformation zone of heavy cylinder rolling is also proposed. In these models, the non-uniform normal strain, non-uniform shear strain, tension and guide roll force are taken into account. To verify the validity of the proposed analytical solution, the analytical heavy cylinder rolling force was compared with the experimental results. Very good agreements are found. The influences of reduction, speed ratio, friction coefficient ratio, guide roll force on rolling force distribution and bending curvature are presented. The simulations show a good potential of these models in industrial application.

The Himalaya in 3D: Slab dynamics controlled mountain building and monsoon intensification

Tectonic models for the Oligocene–Miocene development of the Himalaya mountain range are largely focused on crustal-scale processes, and developed along orogen-perpendicular cross sections. Such models assume uniformity along the length of the Himalaya, but significant along-strike tectonic variations occur, highlighting a need for three-dimensional evolutionary models of Himalayan orogenesis. Here we show a strong temporal correlation of southward motion of the Indian slab relative to the overriding Himalayan orogen, lateral migration of slab detachment, and subsequent dynamic rebound with major changes in Himalayan metamorphism, deformation, and exhumation. Slab detachment was also coeval with South Asian monsoon intensification, which leads us to hypothesize their genetic link. We further propose that anchoring of the Indian continental subducted lithosphere from 30 to 25 Ma steepened the dip of the Himalayan sole thrust, resulting in crustal shortening deep within the Himalayan orogenic wedge. During the subsequent ∼13 m.y., slab detachment propagated inward from both Himalayan syntaxes. Resultant dynamic rebound terminated deep crustal shortening and caused a rapid rise of the mountain range. The increased orography intensified the South Asian monsoon. Decreased compressive forces in response to slab detachment may explain an observed ∼25% decrease in the India-Eurasia convergence rate. The asymmetric curvature of the arc, i.e., broadly open, but tighter to the east, suggests faster slab detachment migration from the west than from the east. Published Lu-Hf garnet dates for eclogite facies metamorphism in the east-central Himalaya as old as ca. 38–34 Ma may offer a test that the new model fails, because the model predicts that such metamorphism would be restricted to middle Miocene time. Alternatively, these dates may provide a case study to test suspicions that Lu-Hf garnet dates can exceed actual ages.

Editorial: Putting the "Why" Back into Bone "Archytecture".

Editorial: Putting the "Why" Back into Bone "Archytecture".

Evaluation of 3C-SiC/Si residual stress and curvatures along different wafer direction

During the heteroepitaxial growth of a thin film on a thick substrate, important stresses arise in the grown material and may influence the physical properties of the film. The residual stresses result in a bending of the substrate/film system. In this work the evaluation of the wafer curvature and the residual stress along different crystallographic directions of the wafer was proposed. Performed by an interferometric optical profilometer, optical microscope and X-ray diffraction analysis, the curvature of the wafer along the [110] and [1−10] wafer directions was observed for hetero-epitaxial Cubic Silicon Carbide (3C-SiC) on Si (001) films. As a consequence of the stress generated during hetero-epitaxy, due to the difference in thermal expansion coefficient and lattice mismatch between the two materials, an asymmetric wafer curvature was observed.

Effect of bidirectional internal flow on fluid.structure interaction dynamics of conveying marine riser model subject to shear current

This article presents a numerical investigation concerning the effect of two kinds of axially progressing internal flows (namely, upward and downward) on fluid.structure interaction (FSI) dynamics about a marine riser model which is subject to external shear current. The CAE technology behind the current research is a proposed FSI solution, which combines structural analysis software with CFD technology together. Efficiency validation for the CFD software was carried out first. It has been proved that the result from numerical simulations agrees well with the observation from relating model test cases in which the fluidity of internal flow is ignorable. After verifying the numerical code accuracy, simulations are conducted to study the vibration response that attributes to the internal progressive flow. It is found that the existence of internal flow does play an important role in determining the vibration mode (/dominant frequency) and the magnitude of instantaneous vibration amplitude. Since asymmetric curvature along the riser span emerges in the case of external shear current, the centrifugal and Coriolis accelerations owing to up- and downward internal progressive flows play different roles in determining the fluid.structure interaction response. The discrepancy between them becomes distinct, when the velocity ratio of internal flow against external shear current is relatively high.

Effect of bidirectional internal flow on fluid–structure interaction dynamics of conveying marine riser model subject to shear current

ABSTRACT This article presents a numerical investigation concerning the effect of two kinds of axially progressing internal flows (namely, upward and downward) on fluid–structure interaction (FSI) dynamics about a marine riser model which is subject to external shear current. The CAE technology behind the current research is a proposed FSI solution, which combines structural analysis software with CFD technology together. Efficiency validation for the CFD software was carried out first. It has been proved that the result from numerical simulations agrees well with the observation from relating model test cases in which the fluidity of internal flow is ignorable. After verifying the numerical code accuracy, simulations are conducted to study the vibration response that attributes to the internal progressive flow. It is found that the existence of internal flow does play an important role in determining the vibration mode (/dominant frequency) and the magnitude of instantaneous vibration amplitude. Since asymmetric curvature along the riser span emerges in the case of external shear current, the centrifugal and Coriolis accelerations owing to up- and downward internal progressive flows play different roles in determining the fluid–structure interaction response. The discrepancy between them becomes distinct, when the velocity ratio of internal flow against external shear current is relatively high.

Effect of upward internal flow on dynamics of riser model subject to shear current

Numerical study about vortex-induced vibration (VIV) related to a flexible riser model in consideration of internal flow progressing inside has been performed. The main objective of this work is to investigate the coupled fluid-structure interaction (FSI) taking place between tensioned riser model, external shear current and upward-progressing internal flow (from ocean bottom to surface). A CAE technology behind the current research which combines structural software with the CFD technology has been proposed. According to the result from dynamic analysis, it has been found that the existence of upward-progressing internal flow does play an important role in determining the vibration mode (/dominant frequency), vibration intensity and the magnitude of instantaneous vibration amplitude, when the velocity ratio of internal flow against external current is relatively high. As a rule, the larger the velocity of internal flow is, the more it contributes to the dynamic vibration response of the flexible riser model. In addition, multi-modal vibration phenomenon has been widely observed, for asymmetric curvature along the riser span emerges in the case of external shear current being imposed.

Controlled Collapse of High‐Aspect‐Ratio Nanostructures

Capillary-force-induced collapse of high-aspect-ratio (HAR) micro- and nanostructures is common in the evaporation-drying process and a number of applications based on the collapse have been proposed. However, the collapse of small HAR structures is usually uncontrollable, which has prevented it from being used in engineering applications. Here, the collapse of 10-nm-scale structures is separately controlled through engineering an asymmetric cross section, curvature, and tilt in the structures prior to collapse. It is shown that this deterministic-collapse approach can be used to create linear structures from collapsed pillars and planar rectangular structures from collapsed fencelike linear structures, and can further be used to create small gaps by controlling the collapse of nearby structures. These techniques could be used to improve the performance of beam-based lithography methods for certain types of patterns by increasing throughput and resolution, reducing the proximity effect, and reducing irradiation damage. In addition, this controlled-collapse concept provides a possible platform with which to study mechanical behavior at the 10-nm scale.

Optimal Synthesis of the Asymmetric Sinistral/Dextral Markov–Dubins Problem

We consider a variation of the classical Markov–Dubins problem dealing with curvature-constrained, shortest paths in the plane with prescribed initial and terminal positions and tangents, when the lower and upper bounds of the curvature of the path are not necessarily equal. The motivation for this problem stems from vehicle navigation applications, when a vehicle may be biased in taking turns at a particular direction due to hardware failures or environmental conditions. After formulating the shortest path problem as a minimum-time problem, a family of extremals, which is sufficient for optimality, is characterized, and subsequently the complete analytic solution of the optimal synthesis problem is presented. In addition, the synthesis problem, when the terminal tangent is free, is also considered, leading to the characterization of the set of points that can be reached in the plane by curves satisfying asymmetric curvature constraints.