scholarly journals All twist and no bend makes raft edges splay: Spontaneous curvature of domain edges in colloidal membranes

2020 ◽  
Vol 6 (31) ◽  
pp. eaba2331 ◽  
Author(s):  
Joia M. Miller ◽  
Doug Hall ◽  
Joanna Robaszewski ◽  
Prerna Sharma ◽  
Michael F. Hagan ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Spontaneous Curvature ◽  
Nonmonotonic Dependence ◽  
Rigid Rods ◽  
Complex Shapes ◽  
Colloidal Membranes ◽  
Long Rod ◽  
Rigid Rod ◽  
Inverse Structure ◽  
Theory And Experiments

Using theory and experiments, we study the interface between two immiscible domains in a colloidal membrane composed of rigid rods of different lengths. Geometric considerations of rigid rod packing imply that a domain of sufficiently short rods in a background membrane of long rods is more susceptible to twist than the inverse structure, a long-rod domain in a short-rod membrane. The midplane tilt at the interdomain edge forces splay, which, in turn, manifests as spontaneous edge curvature with energetics controlled by the length asymmetry of constituent rods. A thermodynamic model of such tilt-curvature coupling at interdomain edges explains a number of experimental observations, including annularly shaped long-rod domains, and a nonmonotonic dependence of edge twist on domain radius. Our work shows how coupling between orientational and compositional degrees of freedom in two-dimensional fluids gives rise to complex shapes of fluid domains, analogous to shape transitions in 3D fluid vesicles.

The Double Seesaw Oscillator in a Windfield: Theory and Experiments

1997 ◽  
Author(s):  
A. H. P. van der Burgh ◽  
T. I. Haaker ◽  
B. W. van Oudheusden
Keyword(s):  
Equilibrium State ◽  
Degrees Of Freedom ◽  
Normal Modes ◽  
Typical Result ◽  
Resonant Case ◽  
Accurate Model ◽  
Codimension Two ◽  
Model Equations ◽  
Theory And Experiments ◽  
Codimension Two Bifurcation

Abstract In this paper the dynamics of an oscillator with two degrees-of-freedom of a double seesaw type in a windtunnel is studied. Model equations for this aeroelastic oscillator are derived and an analysis of these equations is given for the non-resonant case. A typical result is a (local codimension two) bifurcation which describes the transfer from the unstable equilibrium state to one of the two normal modes of the oscillator. Some experimental results are presented from which on may conclude that more accurate model equations should be developed.

Computational Foundations for Using Three Degrees of Freedom Build Platforms to Enable Supportless Extrusion-Based Additive Manufacturing

2019 ◽  
Author(s):  
Prahar M. Bhatt ◽  
Rishi K. Malhan ◽  
Satyandra K. Gupta
Keyword(s):  
Surface Roughness ◽  
Additive Manufacturing ◽  
Manufacturing Systems ◽  
Degrees Of Freedom ◽  
Support Structures ◽  
Complex Shapes ◽  
Build Time ◽  
Time Accuracy ◽  
Three Degrees Of Freedom

Abstract Extrusion-based additive manufacturing systems usually use three degrees of freedom extrusion tools to perform the deposition operation. This requires the use of support structures to deposit structures with overhang features. The use of support structures can be avoided by adding degrees of freedom to the build platform. The elimination of build structures can offer benefits in terms of reduction of build time and elimination of postprocessing costs. This paper demonstrates that the use of three degrees of freedom build platform enables printing of complex shapes without support structures. We present computational foundations for generating paths and trajectories for synchronizing the motion of three degrees of freedom build platforms and three degrees of freedom extrusion tools. We report results on six different test parts in terms of reduction in build time, accuracy, and surface roughness.

Theory and Experiments on the Compliance Control of Redundant Robot Manipulators

1990 ◽  
Vol 112 (4) ◽  
pp. 653-660 ◽  
Author(s):  
H. Kazerooni ◽  
K. G. Bouklas ◽  
J. Guo
Keyword(s):  
Degrees Of Freedom ◽  
Control Method ◽  
Robot Manipulators ◽  
Industrial Robot ◽  
Redundant Robot ◽  
Control Approach ◽  
Six Degrees Of Freedom ◽  
The Stability ◽  
Control Methodology ◽  
Theory And Experiments

This work presents a control methodology for compliant motion in redundant robot manipulators. This control approach takes advantage of the redundancy in the robot’s degrees of freedom: while a maximum six degrees of freedom of the robot control the robot’s endpoint position, the remaining degrees of freedom impose an appropriate force on the environment. To verify the applicability of this control method, an active end-effector is mounted on an industrial robot to generate redundancy in the degrees of freedom. A set of experiments are described to demonstrate the use of this control method in constrained maneuvers. The stability of the robot and the environment is analyzed.

Orientability of Rigid Rodlike Molecules in Solution and Controlled Preparation of Model Systems

1988 ◽  
Vol 134 ◽  
Author(s):  
Jeffrey A. Odell ◽  
Andrew Keller ◽  
Edward D.T. Atkins ◽  
Miklos J. Nagy ◽  
Jose Luis Feijoo ◽  
...  
Keyword(s):  
Rotational Diffusion ◽  
Model Systems ◽  
Specific Reference ◽  
X Ray Diffraction ◽  
Rigid Rods ◽  
Colloid Science ◽  
Rigid Rod ◽  
Separate Line ◽  
The Individual ◽  
Controlled Preparation

ABSTRACTA survey is presented of our works on orientability of poly(p-phenylene-benzbisthiazole) (PBT) as a model for rigid rods. It starts with the solid state with specific reference to diffraction by the individual molecule. It is followed by behaviour in semidilute solutions, demonstrating increase of orientability with increasing rod alignment, with vastly higher absolute values (as expressed by rotational diffusion coefficient) than anticipated from existing theory. The origin of the discrepancy, as identified by simulations, lies in the inappropriateness of the application of mean constraints, a recognition which should have wider implications. The relaxation from the highly oriented state, also in solution, has been followed and the elementary rotational jump of rods identified, with a new method relying on in situ (synchrotron) X-ray diffraction. As a separate line, we are announcing a new model system, ellipsoidal latices of predesigned axial ratios, with wide ranging potential for the study of rigid rod behaviour in polymer and colloid science.

Deterministic Chaos in the Dynamics of a Freely Jointed Chain with Three Degrees of Freedom

1993 ◽  
Vol 48 (4) ◽  
pp. 584-594
Author(s):  
Georg R. Siegert ◽  
Roland G. Winkler ◽  
Peter Reineker
Keyword(s):  
Degrees Of Freedom ◽  
Chaotic Behavior ◽  
Initial Conditions ◽  
Deterministic Chaos ◽  
Power Spectra ◽  
Constrained System ◽  
Rigid Rods ◽  
End Distance ◽  
Poincaré Surfaces Of Section ◽  
Three Degrees Of Freedom

Abstract The dynamics of a short freely jointed chain of three segments is investigated numerically. The chain consists of mass points connected by massless rigid rods, its initial and final points being fixed. Thus the chain represents a holonomically constrained system with three degrees of freedom. It is shown that the motion of the mass points can be chaotic; the occurrence of chaos depends on the initial conditions of the motion, the end-to-end distance of the chain, and the angular momentum about the axis of the stretching direction. Moreover, the chain more likely exhibits regular than chaotic behavior. The numerical results are presented in the form of Poincare surfaces of section, including the use of a slice technique, as well as in the form of power spectra.

A Cable Length Invariant Robotic Tail Using a Circular Shape Universal Joint Mechanism

2019 ◽  
Vol 11 (5) ◽  
Author(s):  
Yujiong Liu ◽  
Jiamin Wang ◽  
Pinhas Ben-Tzvi
Keyword(s):  
Degrees Of Freedom ◽  
Invariance Property ◽  
Kinematic Modeling ◽  
Universal Joint ◽  
Constant Length ◽  
Cable Length ◽  
Workspace Analysis ◽  
Complex Shapes ◽  
Joint Mechanism ◽  
Pitch Bending

This paper presents the development of a new robotic tail based on a novel cable-driven universal joint mechanism. The novel joint mechanism is synthesized by geometric reasoning to achieve the desired cable length invariance property, wherein the mechanism maintains a constant length for the driving cables under universal rotation. This feature is preferable because it allows for the bidirectional pulling of the cables which reduces the requisite number of actuators. After obtaining this new joint mechanism, a serpentine robotic tail with fewer actuators, simpler controls, and a more robust structure is designed and integrated. The new tail includes two independent macro segments (2 degrees of freedom each) to generate more complex shapes (4 degrees of freedom total), which helps with improving the dexterity and versatility of the robot. In addition, the pitch bending and yaw bending of the tail are decoupled due to the perpendicular joint axes. The kinematic modeling, dynamic modeling, and workspace analysis are then explained for the new robotic tail. Three experiments focusing on statics, dynamics, and dexterity are conducted to validate the mechanism and evaluate the new robotic tail's performance.

Shear-induced lateral migration of Brownian rigid rods in parabolic channel flow

1997 ◽  
Vol 332 ◽  
pp. 1-21 ◽  
Author(s):  
Ludwig C. Nitsche ◽  
E. J. Hinch
Keyword(s):  
Degrees Of Freedom ◽  
Transport Coefficients ◽  
Azimuthal Angle ◽  
Polar Angle ◽  
Basis Functions ◽  
Lateral Migration ◽  
Flat Plates ◽  
Rigid Rods ◽  
Effective Transport ◽  
Effective Transport Coefficients

This paper addresses the cross-stream migration of rigid rods undergoing diffusion and advection in parabolic flow between flat plates – a simple model of a polymer that possesses internal (rotational) degrees of freedom for which the probability distribution depends upon the local shear rate. Unequivocal results on the observable concentration profiles across the channel are obtained from a finite–difference solution of the full Fokker–Planck equation in the space of lateral position y and azimuthal angle φ, the polar angle θ being constrained to π/2 for simplicity. Steric confinement and hydrodynamic wall effects, operative within thin boundary layers, are neglected. These calculations indicate that rods should migrate toward the walls. For widely separated rotational and translational timescales asymptotic analysis gives effective transport coefficients for this migration. Based upon angular distributions at arbitrary rotational Péclet number – obtained here by a least–squares collocation method using trigonometric basis functions – accumulation at the walls is confirmed quantitatively by the effective transport coefficients. The results are extended to free rotation using spherical harmonics as the basis functions in the (φ, θ) orientation space. Finally, a critique is given of the traditional thermodynamic arguments for polymer migration as they would apply to purely rotational internal degrees of freedom.

scholarly journals Closed Intramedullar Osteosynthesis in Surgical Treatment of Children with Diaphyseal Femur Fractures

2010 ◽  
Vol 17 (1) ◽  
pp. 60-65
Author(s):  
V M Rozinov ◽  
S I Yandiev ◽  
I A Burkin
Keyword(s):  
Surgical Treatment ◽  
School Age Children ◽  
School Age ◽  
Femur Fractures ◽  
Rigid Rods ◽  
Optimum Technique ◽  
Stable Osteosynthesis ◽  
Bone Fragments ◽  
Rigid Rod ◽  
Open Injuries

Outcomes of surgical treatment for diaphyseal fractures of the femur were analyzed in 270 (278 interventions) out of 509 patients being admitted to the clinic since 1999. In overwhelming majority of patients (226 children) closed intramedullar fixation of bone fragments (231 operations) was performed. Closed intramedullar osteosynthesis was performed using flexible and rigid rods including the locking ones. Elastic-stable osteosynthesis is indicated for the treatment of under school age children with type A1, A2, A3, B1, B2, B3, C2 fractures as well as junior school age children with type A1, A2, B1, B3, C2 fractures. Presented technique can be considered as a gold standard in this group of patients. Closed intramedullary osteosynthesis by rigid rod without locking is the optimum technique for the treatment of junior and senior school age children in bearing injuries of types A3 and B2. Method of choice in senior school age children with A1, A2, B1, B3, C1, C2 and C3 fractures is closed intramedullar osteosynthesis with locking rod. Preliminary extrafocal fixation in multiple and open injuries creates optimum conditions for delayed intramedullar osteosynthesis.

Design and Singularity Analysis for Nine-Bar Mechanism of Three Crank Hybrid Driven

2014 ◽  
Vol 496-500 ◽  
pp. 781-784
Author(s):  
Sheng Tao Song ◽  
Rui Qin Li ◽  
Yan Gao ◽  
Da Hai Li
Keyword(s):  
Mechanical Properties ◽  
Degrees Of Freedom ◽  
Singularity Analysis ◽  
Mechanism Analysis ◽  
Analysis Method ◽  
Loop Analysis ◽  
Two Degrees Of Freedom ◽  
Long Rod ◽  
Existence Conditions

With two degrees of freedom five-bar linkage as the foundation, carry on the multiple loop coupling, built three crank controllable nine bar mechanism similar to that of the crank slider pressing, which can meet the controlled flexible output, and conform to the mechanical properties of crank slider pressing mechanism. We use the loop analysis method to analyze the singularity of the mechanism. Analysis through two steps, first of all analysis on three crank existence conditions and the entire organization singularity, it is concluded that the condition of mechanism dont have singularity, and according to the singular condition carrying on research of singularity position, the long rod assembly condition is obtained.

Layer Spacing of Montmorillonites Modified with Rigid Rods

2007 ◽  
Vol 7 (12) ◽  
pp. 4546-4551
Author(s):  
Lorena Solar ◽  
Rodrigo Navarro ◽  
Clara Gómez ◽  
Helmut Reinecke
Keyword(s):  
Interlayer Distance ◽  
X Ray Diffraction ◽  
Layer Spacing ◽  
X Ray ◽  
Modified Montmorillonite ◽  
Rigid Rods ◽  
Montmorillonite Clays ◽  
Rigid Rod ◽  
Clay Layers ◽  
Oriented Parallel

The dependence of the interlayer distance in modified montmorillonite clays on the length of rigid rod molecules used for clay organophilization is studied. Therefore, a series of fully aromatic compounds of different length functionalized with a terminal amine group has been synthesized and transformed into the corresponding ammonium salts. The interlayer distance is determined by X-ray diffraction, the quantity of the modifier incorporated in the clay is obtained by thermogravimetric analysis. It is shown that the distance between layers in the modified clay does not depend on the length of the modifier used. This fact leads to the conclusion that rigid rods must be oriented parallel to the clay layers. On the other hand, the molar percentage of modifier molecules incorporated in the clay structure depends on the length of the rigid rods in the sense that shorter molecules are considerably easier to incorporate than longer ones.

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