Examine curvature approximation by snake-like driving wire robot -

Author(s):  
Masaharu YOKOMIZO ◽  
Katsuya MIYAMOTO ◽  
Takeshi AOKI
1998 ◽  
Vol 13 (16) ◽  
pp. 2857-2874
Author(s):  
IVER H. BREVIK ◽  
HERNÁN OCAMPO ◽  
SERGEI ODINTSOV

We discuss ε-expansion in curved space–time for asymptotically free and asymptotically nonfree theories. The existence of stable and unstable fixed points is investigated for fϕ4 theory and SU(2) gauge theory. It is shown that ε-expansion maybe compatible with aysmptotic freedom on special solutions of the RG equations in a special ase (supersymmetric theory). Using ε-expansion RG technique, the effective Lagrangian for covariantly constant gauge SU(2) field and effective potential for gauged NJL model are found in (4-ε)-dimensional curved space (in linear curvature approximation). The curvature-induced phase transitions from symmetric phase to asymmetric phase (chromomagnetic vacuum and chiral symmetry broken phase, respectively) are discussed for the above two models.


1955 ◽  
Vol 6 (1) ◽  
pp. 31-45
Author(s):  
H. K. Zienkiewicz

SummarySlender-body theory is used to derive the ogive of curvature approximation for very slender, pointed, convex head shapes at supersonic speeds. Results of application of this approximation, together with the λ-method for circular arc ogives, to a variety of non-slender head shapes show very good agreement with the method of characteristics, van Dyke's second-order theory and experiment. Good agreement with the method of characteristics and with experiment is obtained even in cases when the stagnation pressure losses across the nose shock wave are not negligible.


1997 ◽  
Vol 12 (30) ◽  
pp. 2271-2277 ◽  
Author(s):  
I. L. Buchbinder ◽  
T. Inagaki ◽  
S. D. Odintsov

We investigate the effect of an external gravitational fields to the chiral symmetry breaking in the supersymmetric (SUSY) Nambu–Jona-Lasinio (NJL) model coupled to gravity in a non-supersymmetric way. Evaluating the effective potential in the leading order of the 1/Nc-expansion and in the linear curvature approximation, it is possible to have the chiral symmetry breaking in the SUSY NJL model in an external gravitational fields. In the broken phase the dynamically generated mass is analytically and numerically calculated.


2014 ◽  
Vol 52 (1) ◽  
pp. 679-689 ◽  
Author(s):  
Alexandra Bringer ◽  
Bertrand Chapron ◽  
Alexis Mouche ◽  
Charles-Antoine Guerin

Author(s):  
Fabian Thiery ◽  
Fabian Fritz ◽  
Nikolaus A. Adams ◽  
Stefan Adami

AbstractWe comment on a recent article [Comput. Mech. 2020, 65, 487–502] about surface-tension modeling for free-surface flows with Smoothed Particle Hydrodynamics. The authors motivate part of their work related to a novel principal curvature approximation by the wrong claim that the classical curvature formulation in SPH overestimates the curvature in 3D by a factor of 2. In this note we confirm the correctness of the classical formulation and point out the misconception of the commented article.


2017 ◽  
Vol 36 (3) ◽  
pp. 233
Author(s):  
Ximo Gual-Arnau ◽  
Maria Victoria Ibáñez Gual ◽  
Juan Monterde

We propose an invariant three-point curvature approximation for plane curves based on the arc of a parabolic sector, and we analyze how closely this approximation is to the true curvature of the curve. We compare our results with the obtained with other invariant three-point curvature approximations. Finally, an application is discussed.


Robotica ◽  
2019 ◽  
Vol 37 (5) ◽  
pp. 868-882
Author(s):  
Mahdi Bamdad ◽  
M. Mehdi Bahri

SummaryRecently, the idea of applying “jamming” of appropriate media has been exploited for a novel continuum robot design. It is completed by applying vacuum in a robot structure filled with granular media. The backbone deformation and motion are achieved by controlling the fluid pressure. A jammable robotic manipulator does not certainly follow constant curvature during bending, that is, gravitational loads cause section sag. The kinematics describes the deformation of continuum manipulators. This formulation is expected to facilitate additional synthesis and analysis on workspace. This paper presents a Jacobian-based approach to obtain the forward kinematics solution. The proposed kinematic formulation in this paper tries to combine the key advantages of the techniques in constant curvature and variable curvature models. Hence, the deformation of any arbitrary bending is modeled. The workspace synthesis is continued by kinematic analysis, and in this regard, the manipulability measure is computed. This is an important improvement when compared with existing work for this kind of manipulators. It shows how manipulability measure can determine the workspace quality, where usually reachability is used for robot’s capabilities representation. As a result, the forward kinematics and manipulability analysis based on a piecewise-constant-curvature approximation are discussed in the simulation. The simulation has been carried out according to the fabricated experimental robot.


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