3,560 research outputs found

    Collision Resolutions in Cloth Simulation

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    We present a new collision resolution scheme for cloth collisions. Our main concern is to find dynamically convincing resolutions, i.e. positions and velocities of cloth elements, for any kinds of collisions occuring in cloth simulation (cloth-cloth, cloth-rigid, and cloth-cloth-rigid). We define our cloth surface as connected faces of mass particles where each particle is controlled by its internal energy functions. Our collision resolution method finds appropriate next positions and velocities of particles by conserving the particles’ momentums as accurately as possible. Cloth-cloth collision resolution is a special case of deformable N-body collision resolution. So to solve deformable N-body collision resolutions, we propose a new collision resolution method, which groups cloth particles into parts and resolves collisions between parts using the law of momentum conservation. To resolve collisions, we solve a system of linear equations derived from the collision relationships. A system of linear equations is built using a scheme adapted from the simultaneous resolution method for rigid N-body collisions [1]. For the special case where we can find cyclic relationships in collisions, we solve a system of linear inequalities derived from the collision relationships

    Electrical spin injection and detection in an InAs quantum well

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    We demonstrate fully electrical detection of spin injection in InAs quantum wells. A spin polarized current is injected from a NiFe thin film to a two-dimensional electron gas (2DEG) made of InAs based epitaxial multi-layers. Injected spins accumulate and diffuse out in the 2DEG, and the spins are electrically detected by a neighboring NiFe electrode. The observed spin diffusion length is 1.8 um at 20 K. The injected spin polarization across the NiFe/InAs interface is 1.9% at 20 K and remains at 1.4% even at room temperature. Our experimental results will contribute significantly to the realization of a practical spin field effect transistor

    Regular projections of graphs with at most three double points

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    A generic immersion of a planar graph into the 2-space is said to be knotted if there does not exist a trivial embedding of the graph into the 3-space obtained by lifting the immersion with respect to the natural projection from the 3-space to the 2-space. In this paper we show that if a generic immersion of a planar graph is knotted then the number of double points of the immersion is more than or equal to three. To prove this, we also show that an embedding of a graph obtained from a generic immersion of the graph (does not need to be planar) with at most three double points is totally free if it contains neither a Hopf link nor a trefoil knot.Comment: 16 pages, 31 figure

    Soft-mode turbulence in electrohydrodynamic convection of a homeotropically aligned nematic layer

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    The experimental study of electroconvection in a homeotropically aligned nematic ~MBBA! is reported. Thesystem undergoes a supercritical bifurcation ‘‘rest state-spatiotemporal chaos.’’ The chaos is caused by longwavelengthmodulation of the orientation of convective rolls. For the first time the observations both below andbeyond the Lifshitz point are accompanied by quantitative analysis of temporal autocorrelation functions ofturbulent modes. The dependence of the correlation time on the control parameter is obtained. A secondarybifurcation from normal to abnormal rolls is discussed

    Dynamic Simulation for Zero-Gravity Activities

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    Working and training for space activities is difficult in terrestrial environments. We approach this crucial aspect of space human factors through 3D computer graphics dynamics simulation of crewmembers, their tasks, and physics-based movement modeling. Such virtual crewmembers may be used to design tasks and analyze their physical workload to maximize success and safety without expensive physical mockups or partially realistic neutral-buoyancy tanks. Among the software tools we have developed are methods for fully articulated 3D human models and dynamic simulation. We are developing a fast recursive dynamics algorithm for dynamically simulating articulated 3D human models, which comprises kinematic chains - serial, closed-loop, and tree-structure - as well as the inertial properties of the segments. Motion planning is done by first solving the inverse kinematic problem to generate possible trajectories, and then by solving the resulting nonlinear optimal control problem. For example, the minimization of the torques during a simulation under certain constraints is usually applied and has its origin in the biomechanics literature. Examples of space activities shown are zero-gravity self orientation and ladder traversal. Energy expenditure is computed for the traversal task

    Coccoliths and Related Calcareous Nannofossils from the Upper Cretaceous Fencepost Limestone of Northwestern Kansas

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    17-22http://deepblue.lib.umich.edu/bitstream/2027.42/48470/2/ID320.pd
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