273 research outputs found
Numerical investigation of effective nonlinear coefficient model for coupled third harmonic generation
In this paper, the optimal solution of effective nonlinear coefficient of
quasi-phase-matching (QPM) crystals for coupled third harmonic generation
(CTHG) was numerically investigated. The effective nonlinear coefficient of
CTHG was converted to an Ising model for optimizing domain length distributions
of aperiodically poled lithium niobate (APPLN) crystals with lengths as 0.5 mm
and 1 mm, and fundamental wavelengths ranging from 1000 nm to 6000 nm. A method
for reconstructing crystal domain poling weight curve of coupled nonlinear
processes was also proposed, which demonstrated the optimal conversion ratio
between two coupled nonlinear processes at each place along the crystal. In
addition, by applying the semidefinite programming, the upper bound on the
effective nonlinear coefficients deff for different fundamental wavelengths
were calculated. The research can be extended to any coupled dual \c{hi}(2)
process and will help us to understand better the dynamics of coupled nonlinear
interactions based on QPM crystals.Comment: 16 page
Online Nash Welfare Maximization Without Predictions
Nash welfare maximization is widely studied because it balances efficiency
and fairness in resource allocation problems. Banerjee, Gkatzelis, Gorokh, and
Jin (2022) recently introduced the model of online Nash welfare maximization
with predictions for divisible items and agents with additive
utilities. They gave online algorithms whose competitive ratios are
logarithmic. We initiate the study of online Nash welfare maximization
\emph{without predictions}, assuming either that the agents' utilities for
receiving all items differ by a bounded ratio, or that their utilities for the
Nash welfare maximizing allocation differ by a bounded ratio. We design online
algorithms whose competitive ratios only depend on the logarithms of the
aforementioned ratios of agents' utilities and the number of agents
Identification of Causal Structure with Latent Variables Based on Higher Order Cumulants
Causal discovery with latent variables is a crucial but challenging task.
Despite the emergence of numerous methods aimed at addressing this challenge,
they are not fully identified to the structure that two observed variables are
influenced by one latent variable and there might be a directed edge in
between. Interestingly, we notice that this structure can be identified through
the utilization of higher-order cumulants. By leveraging the higher-order
cumulants of non-Gaussian data, we provide an analytical solution for
estimating the causal coefficients or their ratios. With the estimated (ratios
of) causal coefficients, we propose a novel approach to identify the existence
of a causal edge between two observed variables subject to latent variable
influence. In case when such a causal edge exits, we introduce an asymmetry
criterion to determine the causal direction. The experimental results
demonstrate the effectiveness of our proposed method.Comment: Accepted by AAAI 202
Code Generation as a Dual Task of Code Summarization
Code summarization (CS) and code generation (CG) are two crucial tasks in the
field of automatic software development. Various neural network-based
approaches are proposed to solve these two tasks separately. However, there
exists a specific intuitive correlation between CS and CG, which have not been
exploited in previous work. In this paper, we apply the relations between two
tasks to improve the performance of both tasks. In other words, exploiting the
duality between the two tasks, we propose a dual training framework to train
the two tasks simultaneously. In this framework, we consider the dualities on
probability and attention weights, and design corresponding regularization
terms to constrain the duality. We evaluate our approach on two datasets
collected from GitHub, and experimental results show that our dual framework
can improve the performance of CS and CG tasks over baselines.Comment: To appear at the 33rd Conference on Neural Information Processing
Systems (NeurIPS) 201
Supercontinuum generation and carrier envelope offset frequency measurement in a tapered single-mode fiber
We report supercontinuum generation by launching femtosecond Yb fiber laser
pulses into a tapered single-mode fiber of 3 um core diameter. A spectrum of
more than one octave, from 550 to 1400 nm, has been obtained with an output
power of 1.3 W at a repetition rate of 250 MHz, corresponding to a coupling
efficiency of up to 60%. By using a typical f-2f interferometer, the carrier
envelope offset frequency was measured and found to have a signal-to-noise
ratio of nearly 30 dB.Comment: 10 pages, accepted by Appl Phys
SelFLoc: Selective Feature Fusion for Large-scale Point Cloud-based Place Recognition
Point cloud-based place recognition is crucial for mobile robots and
autonomous vehicles, especially when the global positioning sensor is not
accessible. LiDAR points are scattered on the surface of objects and buildings,
which have strong shape priors along different axes. To enhance message passing
along particular axes, Stacked Asymmetric Convolution Block (SACB) is designed,
which is one of the main contributions in this paper. Comprehensive experiments
demonstrate that asymmetric convolution and its corresponding strategies
employed by SACB can contribute to the more effective representation of point
cloud feature. On this basis, Selective Feature Fusion Block (SFFB), which is
formed by stacking point- and channel-wise gating layers in a predefined
sequence, is proposed to selectively boost salient local features in certain
key regions, as well as to align the features before fusion phase. SACBs and
SFFBs are combined to construct a robust and accurate architecture for point
cloud-based place recognition, which is termed SelFLoc. Comparative
experimental results show that SelFLoc achieves the state-of-the-art (SOTA)
performance on the Oxford and other three in-house benchmarks with an
improvement of 1.6 absolute percentages on mean average recall@1
- …