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[en] Coarsegraining is a systematic way of reducing the number of degrees of freedom representing a system of interest. Several coarsegraining techniques have so far been developed, such as iterative Boltzmann inversion, forcematching, and inverse Monte Carlo. However, there is no unified framework that implements these methods and allows their direct comparison. We present a versatile objectoriented toolkit for coarsegraining applications that implements these techniques and provides a flexible modular platform for the further development of coarsegraining techniques. All methods are illustrated and compared by coarsegraining the SPCE water model and liquid propane.
[en] Highlights: • We develop theory for the rovibrational spectra of extremely flexible molecules. • An extremely flexible molecule has no well-defined structure. • Protonated methane is the prototype example. • We successfully describe the nuclear motion as that of a molecular superrotor. • For the superrotor has SO(5) symmetry. This paper treats the low energy rotation-vibration problem in , an extremely flexible molecule lacking a well-defined structure. Using SO(5) symmetry it determines zeroth order energies, and complete nuclear permutation S5 symmetries, using a five-dimensional model involving rotation and two vibrations (which one might imagine as two different “cooperative” HCH bends). These two vibrations are presumed to be unhindered by the molecular potential function and their analytical form is not determined. The other ten vibrational degrees of freedom are presumed to be “rigid” (or averaged over). The general energy expression for this “rigid superrotor” is obtained as where B is the rotational constant and the non-negative integers and satisfy . The superrotor predictions agree favourably with the available experimental data. Applications of the superrotor model to extremely flexible molecules other than are discussed.
[en] supergravity is known to contain a ghost mode associated with higher-derivative terms if it contains with greater than two. We remove the ghost in supergravity by introducing auxiliary gauge field to absorb the ghost. We dub this method as the ghostbuster mechanism https://doi.org/10.1007/JHEP09(2016)106. We show that the mechanism removes the ghost supermultiplet but also terms including with , after integrating out auxiliary degrees of freedom. For pure supergravity case, there appears an instability in the resultant scalar potential. We then show that the instability of the scalar potential can be cured by introducing matter couplings in such a way that the system has a stable potential.
[en] A high precision redundant robotic manipulator for overcoming contents imposed by obstacles or imposed by a highly congested work space is disclosed. One embodiment of the manipulator has four degrees of freedom and another embodiment has seven degrees of freedom. Each of the embodiments utilize a first selective compliant assembly robot arm (SCARA) configuration to provide high stiffness in the vertical plane, a second SCARA configuration to provide high stiffness in the horizontal plane. The seven degree of freedom embodiment also utilizes kinematic redundancy to provide the capability of avoiding obstacles that lie between the base of the manipulator and the end effector or link of the manipulator. These additional three degrees of freedom are added at the wrist link of the manipulator to provide pitch, yaw and roll. The seven degrees of freedom embodiment uses one revolute point per degree of freedom. For each of the revolute joints, a harmonic gear coupled to an electric motor is introduced, and together with properly designed based servo controllers provide an end point repeatability of less than 10 microns. 3 figs
[en] This paper focuses on design and implementation of a biomimetic dexterous humanoid hand. Several design rules are proposed to retain human form and functionality in a robotic hand while overcoming the difficultly of actuation within a confined geometry. Size and weight have been optimized in order to achieve human-like performance with the prime objective of typing on a computer keyboard. Each finger has four joints and three degrees of freedom (DOF) while the thumb has an additional degree of freedom necessary for manipulating small objects. The hand consists of 16 servo motors dedicated to finger motion and three motors for wrist motion. A closed-loop kinematic control scheme utilizing the Denavit–Hartenberg convention for spatial joint positioning was implemented. Servo motors housed in the forearm act as an origin for wires to travel to their insertion points in the hand. The dexterity of the DART hand was measured by quantifying functionality and typing speed on a standard keyboard. The typing speed of a single DART hand was found to be 20 words min−1. In comparison, the average human has a typing speed of 33 words min−1 with two hands
[en] Growing data volume of masks tremendously increases manufacture cost. The cost increase is partially due to the complicated optical proximity corrections applied on mask design. In this paper, a yield-aware dissection method is presented. Based on the recognition of yield related mask context, the dissection result provides sufficient degrees of freedom to keep fidelity on critical sites while still retaining the frugality of modified designs. Experiments show that the final mask volume using the new method is reduced to about 50% of the conventional method. (semiconductor technology)
[en] Previous derivations of the BTZ black hole entropy from a dual conformal description place the degrees of freedom at spatial infinity. Here it is shown for the non-rotating case that a dual conformal description exists at any location around the black hole, a result that has a strong physical appeal considering that in 2 + 1-dimensions there are no propagating degrees of freedom in the classical theory. Two copies of the central charge of are recovered, and the microcanonical Cardy formula yields the correct Bekenstein–Hawking entropy. (paper)
[en] In recent years we have witnessed a concentrated effort to make sense of thermodynamics for small-scale systems. One of the main difficulties is to capture a suitable notion of work that models realistically the purpose of quantum machines, in an analogous way to the role played, for macroscopic machines, by the energy stored in the idealisation of a lifted weight. Despite several attempts to resolve this issue by putting forward specific models, these are far from realistically capturing the transitions that a quantum machine is expected to perform. In this work, we adopt a novel strategy by considering arbitrary kinds of systems that one can attach to a quantum thermal machine and defining work quantifiers . These are functions that measure the value of a transition and generalise the concept of work beyond those models familiar from phenomenological thermodynamics. We do so by imposing simple operational axioms that any reasonable work quantifier must fulfil and by deriving from them stringent mathematical condition with a clear physical interpretation. Our approach allows us to derive much of the structure of the theory of thermodynamics without taking the definition of work as a primitive. We can derive, for any work quantifier , a quantitative second law in the sense of bounding the work that can be performed using some non-equilibrium resource by the work that is needed to create it. We also discuss in detail the role of reversibility and correlations in connection with the second law. Furthermore, we recover the usual identification of work with energy in degrees of freedom with vanishing entropy as a particular case of our formalism. Our mathematical results can be formulated abstractly and are general enough to carry over to other resource theories than quantum thermodynamics. (paper)
[en] For electron-phonon Hamiltonians with the couplings linear in the phonon operators, we construct a class of unitary transformations that separate the normal modes into two groups. The modes in the first group interact with the electronic degrees of freedom directly. The modes in the second group interact directly only with the modes in the first group but not with the electronic system. These transformations can be carried out independently for different types of phonon modes, e.g., high- versus low-frequency phonon bands. This construction generalizes recently introduced transformations for systems exhibiting a conical intersection topology. The separation of the normal modes into several groups allows one to develop new approximation schemes. We apply one of such schemes to study electronic relaxation at a semiconducting polymer interface.