2,837 research outputs found
Object oriented finite element analysis: a distributed approach to mesh generation
The object-oriented finite element method (OOFEM) has attracted the attention of many researchers. Compared with the traditional finite element method, OOFEM software has the advantages of maintenance and reuse. Moreover, it is easier to expand the architecture to a distributed one. In this paper, we introduce a distributed architecture of a object-oriented finite element preprocessor. A comparison between the distributed system and the centralised system shows that the former, presented in the paper, greatly improves the performance of mesh generation. Other finite element analysis modules could be expanded according to this architecture. <br /
Multi-group frequency hopping OFDMA based on statistical multiplexing
In this paper, the multi-group frequency hopping OFDMA (MG-FH OFDMA) based on the statistical multiplexing is proposed for the downlink cellular system. Compared with the existed random frequency hopping OFDMA (RFH-OFDMA) system utilizing the statistical multiplexing, the proposed MG-FH OFDMA invokes the deterministic hopping pattern to reduce the number of subcarrier collisions. By dividing all users into different groups, the subcarriers are utilized sufficiently. Latin Square hopping pattern and user index updating scheme are applied to randomize the subcarrier collisions among users. The user capacity, defined as the maximum number of users served with a basic data-rate in a cell, is calculated with the consideration of intra-cell capacity and the other cell interference (OCI). Results show that the proposed MG-FH OFDMA achieves higher user capacity than that of the RFH-OFDMA
Approximate minimum BER power allocation for MIMO-THP system
This paper proposes a transmit power allocation (TPA) scheme based on multiple-input multiple-output (MIMO) Tomlinson-Harashima precoding (THP) structure, where a TPA matrix is introduced to the conventional MIMO-THP. We analyze the influence of the introduced TPA matrix on the performance of MIMO-THP. The proposed TPA scheme invokes the minimum average uncoded bit-error rate (BER) criterion subjected to a sum-power constraint. During the derivation, we consider the effects of precoding loss factor on the TPA scheme and obtain a closed-form expression of the TPA. Compared to existing TPA methods for MIMO-THP systems, the proposed scheme reduces processing complexity and improves the BER performance
Recent advances in copper-catalyzed propargylic substitution
AbstractThe copper-catalyzed propargylic substitution reaction has become a powerful synthetic method to prepare the compounds containing the propargylic subunit. Compared with the other transition-metals applied in the propargylic substitution, copper has many obvious advantages, such as much more inexpensive, easier to handle, milder reaction condition, and higher selectivity. This digest summarizes the recent development in the copper-catalyzed propargylic substitutions with various nitrogen, carbon, oxygen, and sulfur nucleophiles. In addition, the cycloadditions involving the copper-catalyzed propargylic substitution as the key step are included
Optical LC-like resonances in high-index particles
Electric LC resonances, occurring in metallic circuits, govern the motion of
free electrons or electric signals. In this paper, we study the optical LC-like
resonances, which take place in high-index particles (HIPs) and involve optical
or electromagnetic fields instead. The resonance effect is dominated by optical
analogues of inductance and capacitance, which can be determined according to
the electromagnetic energy bounded near the particle. The viewpoint of
dielectric optical circuit with equivalent parameters facilitates the
understanding of dielectric resonance effect. The result also provides a method
for studying the optical properties of the HIPs.Comment: 17 pages, 5 figure
Stark many-body localization with long-range interactions
In one-dimensional (1D) disorder-free interacting systems, a sufficiently
strong linear potential can induce localization of the many-body eigenstates, a
phenomenon dubbed as Stark many-body localization (MBL). In this paper, we
investigate the fate of Stark MBL in 1D spinless fermions systems with
long-range interactions, specifically focusing on the role of interaction
strength. We obtain the Stark MBL phase diagrams by computing the mean gap
ratio and many-body inverse participation ratio at half-filling. We show that,
for short-range interactions, there is a qualitative symmetry between the
limits of weak and strong interactions. However, this symmetry is absent in the
case of long-range interactions, where the system is always Stark many-body
localized at strong interactions, regardless of the linear potential strength.
Furthermore, we study the dynamics of imbalance and entanglement with various
initial states using time-dependent variational principle (TDVP) numerical
methods. We reveal that the dynamical quantities display a strong dependence on
the initial conditions, which suggests that the Hilbert-space fragmentation
precludes thermalization. Our results demonstrate the robustness of Stark MBL
even in the presence of long-range interactions and offer an avenue to explore
MBL in disorder-free systems with long-range interactions
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