7 research outputs found
Asymmetric Diels-Alder Reaction of 5,5,5-Trichloro-3-penten-2-one and Its Related Compound
Diels-Alder reactions of 5,5,5-trichloro-3-penten-2-one and ethyl 4,4,4-trichloro-2-butenoate with cyclopentadiene in the presence of a chiral Lewis acid gave exo-2-acetyl-endo-3-trichloromethyl-bicyclo[2.2.1]hept-5-ene and exo-2-ethoxycarbonyl-endo-3-trichloromethylbicyclo[2.2.1]hept-5-ene with 40% and 7% e.e., respectively
Producing alternating gait on uncoupled feline hindlimbs: muscular unloading rule on a biomimetic robot
Studies on decerebrate walking cats have shown that phase transition is strongly related to muscular sensory signals at limbs. To further investigate the role of such signals terminating the stance phase, we developed a biomimetic feline platform. Adopting link lengths and moment arms from an Acinonyx jubatus, we built a pair of hindlimbs connected to a hindquarter and attached it to a sliding strut, simulating solid forelimbs. Artificial pneumatic muscles simulate biological muscles through a control method based on EMG signals from walking cats (Felis catus). Using the bio-inspired muscular unloading rule, where a decreasing ground reaction force triggers phase transition, stable walking on a treadmill was achieved. Finally, an alternating gait is possible using the unloading rule, withstanding disturbances and systematic muscular changes, not only contributing to our understanding on how cats may walk, but also helping develop better legged robots.The authors acknouledge the Japanese Research Grant KAKENHI Kiban 23220004 and 25540117.This is the author accepted manuscript. The final version is available from Taylor & Francis via http://dx.doi.org/10.1080/01691864.2013.87049
The Whitham Deformation of the Dijkgraaf-Vafa Theory
We discuss the Whitham deformation of the effective superpotential in the
Dijkgraaf-Vafa (DV) theory. It amounts to discussing the Whitham deformation of
an underlying (hyper)elliptic curve. Taking the elliptic case for simplicity we
derive the Whitham equation for the period, which governs flowings of branch
points on the Riemann surface. By studying the hodograph solution to the
Whitham equation it is shown that the effective superpotential in the DV theory
is realized by many different meromorphic differentials. Depending on which
meromorphic differential to take, the effective superpotential undergoes
different deformations. This aspect of the DV theory is discussed in detail by
taking the N=1^* theory. We give a physical interpretation of the deformation
parameters.Comment: 35pages, 1 figure; v2: one section added to give a physical
interpretation of the deformation parameters, one reference added, minor
corrections; v4: minor correction
Exploring muscular contribution during stepping of biomimetic feline hindlimbs
This is the accepted manuscript. The final version is available at http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=6739573&tag=1.Although robotic locomotion have greatly advanced
over the past years, the abyss that separates such locomotion
from even the simplest animal locomotions prompt us to
approach robotic locomotion taking cues from animals. The animal
musculoskeletal structure, often ignored by roboticists due
to its high redundancy and complexity, might hold the secret
for self-stable locomotion observed in bipeds and quadrupeds.
Aiming to better understand how muscles contribute to selfstable
locomotion we take the feline structure as a model on
a biomimetic approach. Using 6 air muscles per hindlimb to
mimic real muscles, this robot walks stably on a treadmill while
supported by a slider, simulating forelimbs. We individually
evaluate muscle contribution to walking stability, performing a
comparison between mono and biarticular synergistic muscles
at the ankle and concluding that a higher compliance on
the biarticular muscle improved walking stability. A better
understanding of such complex phenomena may help on the
development of better legged robots in the future, truly taking
advantage of concepts developed by nature over the years.This work was partially supported by KAKENHI Kiban(S) 23220004