42,706 research outputs found
High-Performance Shuffle Motor Fabricated by Vertical Trench Isolation Technology
Shuffle motors are electrostatic stepper micromotors that employ a built-in mechanical leverage to produce large output forces as well as high resolution displacements. These motors can generally move only over predefined paths that served as driving electrodes. Here, we present the design, modeling and experimental characterization of a novel shuffle motor that moves over an unpatterned, electrically grounded surface. By combining the novel design with an innovative micromachining method based on vertical trench isolation, we have greatly simplified the fabrication of the shuffle motors and significantly improved their overall performance characteristics and reliability. Depending on the propulsion voltage, our motor with external dimensions of 290 μm × 410 mm displays two distinct operational modes with adjustable step sizes varying respectively from 0.6 to 7 nm and from 49 to 62 nm. The prototype was driven up to a cycling frequency of 80 kHz, showing nearly linear dependence of its velocity with frequency and a maximum velocity of 3.6 mm/s. For driving voltages of 55 V, the device had a maximum travel range of ±70 μm and exhibited an output force of 1.7 mN, resulting in the highest force and power densities reported so far for an electrostatic micromotor. After five days of operation, it had traveled a cumulative distance of more than 1.5 km in 34 billion steps without noticeable deterioration in performance.\u
Effects of surface forces and phonon dissipation in a three-terminal nano relay
We have performed a theoretical analysis of the operational characteristics
of a carbon-nanotube-based three-terminal nanorelay. We show that short range
and van der Waals forces have a significant impact on the characteristics of
the relay and introduce design constraints. We also investigate the effects of
dissipation due to phonon excitation in the drain contact, which changes the
switching time scales of the system, decreasing the longest time scale by two
orders of magnitude. We show that the nanorelay can be used as a memory element
and investigate the dynamics and properties of such a device
Optimization and evaluation of variability in the programming window of a flash cell with molecular metal-oxide storage
We report a modeling study of a conceptual nonvolatile memory cell based on inorganic molecular metal-oxide clusters as a storage media embedded in the gate dielectric of a MOSFET. For the purpose of this paper, we developed a multiscale simulation framework that enables the evaluation of variability in the programming window of a flash cell with sub-20-nm gate length. Furthermore, we studied the threshold voltage variability due to random dopant fluctuations and fluctuations in the distribution of the molecular clusters in the cell. The simulation framework and the general conclusions of our work are transferrable to flash cells based on alternative molecules used for a storage media
Afterlive: A performant code for Vlasov-Hybrid simulations
A parallelized implementation of the Vlasov-Hybrid method [Nunn, 1993] is
presented. This method is a hybrid between a gridded Eulerian description and
Lagrangian meta-particles. Unlike the Particle-in-Cell method [Dawson, 1983]
which simply adds up the contribution of meta-particles, this method does a
reconstruction of the distribution function in every time step for each
species. This interpolation method combines meta-particles with different
weights in such a way that particles with large weight do not drown out
particles that represent small contributions to the phase space density. These
core properties allow the use of a much larger range of macro factors and can
thus represent a much larger dynamic range in phase space density.
The reconstructed phase space density is used to calculate momenta of the
distribution function such as the charge density . The charge density
is also used as input into a spectral solver that calculates the
self-consistent electrostatic field which is used to update the particles for
the next time-step.
Afterlive (A Fourier-based Tool in the Electrostatic limit for the Rapid
Low-noise Integration of the Vlasov Equation) is fully parallelized using MPI
and writes output using parallel HDF5. The input to the simulation is read from
a JSON description that sets the initial particle distributions as well as
domain size and discretization constraints. The implementation presented here
is intentionally limited to one spatial dimension and resolves one or three
dimensions in velocity space. Additional spatial dimensions can be added in a
straight forward way, but make runs computationally even more costly.Comment: Accepted for publication in Computer Physics Communication
A GPU-accelerated Direct-sum Boundary Integral Poisson-Boltzmann Solver
In this paper, we present a GPU-accelerated direct-sum boundary integral
method to solve the linear Poisson-Boltzmann (PB) equation. In our method, a
well-posed boundary integral formulation is used to ensure the fast convergence
of Krylov subspace based linear algebraic solver such as the GMRES. The
molecular surfaces are discretized with flat triangles and centroid
collocation. To speed up our method, we take advantage of the parallel nature
of the boundary integral formulation and parallelize the schemes within CUDA
shared memory architecture on GPU. The schemes use only
size-of-double device memory for a biomolecule with triangular surface
elements and partial charges. Numerical tests of these schemes show
well-maintained accuracy and fast convergence. The GPU implementation using one
GPU card (Nvidia Tesla M2070) achieves 120-150X speed-up to the implementation
using one CPU (Intel L5640 2.27GHz). With our approach, solving PB equations on
well-discretized molecular surfaces with up to 300,000 boundary elements will
take less than about 10 minutes, hence our approach is particularly suitable
for fast electrostatics computations on small to medium biomolecules
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