954 research outputs found
Full Hydrodynamic Model of Nonlinear Electromagnetic Response in Metallic Metamaterials
Applications of metallic metamaterials have generated significant interest in
recent years. Electromagnetic behavior of metamaterials in the optical range is
usually characterized by a local-linear response. In this article, we develop a
finite-difference time-domain (FDTD) solution of the hydrodynamic model that
describes a free electron gas in metals. Extending beyond the local-linear
response, the hydrodynamic model enables numerical investigation of nonlocal
and nonlinear interactions between electromagnetic waves and metallic
metamaterials. By explicitly imposing the current continuity constraint, the
proposed model is solved in a self-consistent manner. Charge, energy and
angular momentum conservation laws of high-order harmonic generation have been
demonstrated for the first time by the Maxwell-hydrodynamic FDTD model. The
model yields nonlinear optical responses for complex metallic metamaterials
irradiated by a variety of waveforms. Consequently, the multiphysics model
opens up unique opportunities for characterizing and designing nonlinear
nanodevices.Comment: 11 pages, 14 figure
Cooperative Beamforming Design for Multiple RIS-Assisted Communication Systems
Reconfigurable intelligent surface (RIS) provides a promising way to build
programmable wireless transmission environments. Owing to the massive number of
controllable reflecting elements on the surface, RIS is capable of providing
considerable passive beamforming gains. At present, most related works mainly
consider the modeling, design, performance analysis and optimization of
single-RIS-assisted systems. Although there are a few of works that investigate
multiple RISs individually serving their associated users, the cooperation
among multiple RISs is not well considered as yet. To fill the gap, this paper
studies a cooperative beamforming design for multi-RIS-assisted communication
systems, where multiple RISs are deployed to assist the downlink communications
from a base station to its users. To do so, we first model the general channel
from the base station to the users for arbitrary number of reflection links.
Then, we formulate an optimization problem to maximize the sum rate of all
users. Analysis shows that the formulated problem is difficult to solve due to
its non-convexity and the interactions among the decision variables. To solve
it effectively, we first decouple the problem into three disjoint subproblems.
Then, by introducing appropriate auxiliary variables, we derive the closed-form
expressions for the decision variables and propose a low-complexity cooperative
beamforming algorithm. Simulation results have verified the effectiveness of
the proposed algorithm through comparison with various baseline methods.
Furthermore, these results also unveil that, for the sum rate maximization,
distributing the reflecting elements among multiple RISs is superior to
deploying them at one single RIS
Configuration and capacitance properties of polypyrrole/aligned carbon nanotubes synthesized by electropolymerization
Stator Design Aspects for Permanent Magnet Super-conducting Wind Power Generators
This paper presents an electromagnetic design of a permanent magnet superconducting wind power generator with different stator teeth structures and armature winding arrangements. The main contribution of this paper is that a novel stator configuration is proposed, which is beneficial for superconducting machines. The topology of tapering poles makes it possible for the machine to carry larger current without severe magnetic saturation in the stator teeth. Meantime, the distributed arrangement of wires in the stator slot can reduce the ac loss in the same output power condition. Finite element analysis with commercial software is used to support these results
Acceleration for Timing-Aware Gate-Level Logic Simulation with One-Pass GPU Parallelism
Witnessing the advancing scale and complexity of chip design and benefiting
from high-performance computation technologies, the simulation of Very Large
Scale Integration (VLSI) Circuits imposes an increasing requirement for
acceleration through parallel computing with GPU devices. However, the
conventional parallel strategies do not fully align with modern GPU abilities,
leading to new challenges in the parallelism of VLSI simulation when using GPU,
despite some previous successful demonstrations of significant acceleration. In
this paper, we propose a novel approach to accelerate 4-value logic
timing-aware gate-level logic simulation using waveform-based GPU parallelism.
Our approach utilizes a new strategy that can effectively handle the dependency
between tasks during the parallelism, reducing the synchronization requirement
between CPU and GPU when parallelizing the simulation on combinational
circuits. This approach requires only one round of data transfer and hence
achieves one-pass parallelism. Moreover, to overcome the difficulty within the
adoption of our strategy in GPU devices, we design a series of data structures
and tune them to dynamically allocate and store new-generated output with
uncertain scale. Finally, experiments are carried out on industrial-scale
open-source benchmarks to demonstrate the performance gain of our approach
compared to several state-of-the-art baselines
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