93 research outputs found
Flow Straight and Fast: Learning to Generate and Transfer Data with Rectified Flow
We present rectified flow, a surprisingly simple approach to learning
(neural) ordinary differential equation (ODE) models to transport between two
empirically observed distributions \pi_0 and \pi_1, hence providing a unified
solution to generative modeling and domain transfer, among various other tasks
involving distribution transport. The idea of rectified flow is to learn the
ODE to follow the straight paths connecting the points drawn from \pi_0 and
\pi_1 as much as possible. This is achieved by solving a straightforward
nonlinear least squares optimization problem, which can be easily scaled to
large models without introducing extra parameters beyond standard supervised
learning. The straight paths are special and preferred because they are the
shortest paths between two points, and can be simulated exactly without time
discretization and hence yield computationally efficient models. We show that
the procedure of learning a rectified flow from data, called rectification,
turns an arbitrary coupling of \pi_0 and \pi_1 to a new deterministic coupling
with provably non-increasing convex transport costs. In addition, recursively
applying rectification allows us to obtain a sequence of flows with
increasingly straight paths, which can be simulated accurately with coarse time
discretization in the inference phase. In empirical studies, we show that
rectified flow performs superbly on image generation, image-to-image
translation, and domain adaptation. In particular, on image generation and
translation, our method yields nearly straight flows that give high quality
results even with a single Euler discretization step
Passage-Mask: A Learnable Regularization Strategy for Retriever-Reader Models
Retriever-reader models achieve competitive performance across many different
NLP tasks such as open question answering and dialogue conversations. In this
work, we notice these models easily overfit the top-rank retrieval passages and
standard training fails to reason over the entire retrieval passages. We
introduce a learnable passage mask mechanism which desensitizes the impact from
the top-rank retrieval passages and prevents the model from overfitting.
Controlling the gradient variance with fewer mask candidates and selecting the
mask candidates with one-shot bi-level optimization, our learnable
regularization strategy enforces the answer generation to focus on the entire
retrieval passages. Experiments on different tasks across open question
answering, dialogue conversation, and fact verification show that our method
consistently outperforms its baselines. Extensive experiments and ablation
studies demonstrate that our method can be general, effective, and beneficial
for many NLP tasks.Comment: EMNLP 202
Certified Monotonic Neural Networks
Learning monotonic models with respect to a subset of the inputs is a
desirable feature to effectively address the fairness, interpretability, and
generalization issues in practice. Existing methods for learning monotonic
neural networks either require specifically designed model structures to ensure
monotonicity, which can be too restrictive/complicated, or enforce monotonicity
by adjusting the learning process, which cannot provably guarantee the learned
model is monotonic on selected features. In this work, we propose to certify
the monotonicity of the general piece-wise linear neural networks by solving a
mixed integer linear programming problem.This provides a new general approach
for learning monotonic neural networks with arbitrary model structures. Our
method allows us to train neural networks with heuristic monotonicity
regularizations, and we can gradually increase the regularization magnitude
until the learned network is certified monotonic. Compared to prior works, our
approach does not require human-designed constraints on the weight space and
also yields more accurate approximation. Empirical studies on various datasets
demonstrate the efficiency of our approach over the state-of-the-art methods,
such as Deep Lattice Networks
Post-training Quantization with Multiple Points: Mixed Precision without Mixed Precision
We consider the post-training quantization problem, which discretizes the
weights of pre-trained deep neural networks without re-training the model. We
propose multipoint quantization, a quantization method that approximates a
full-precision weight vector using a linear combination of multiple vectors of
low-bit numbers; this is in contrast to typical quantization methods that
approximate each weight using a single low precision number. Computationally,
we construct the multipoint quantization with an efficient greedy selection
procedure, and adaptively decides the number of low precision points on each
quantized weight vector based on the error of its output. This allows us to
achieve higher precision levels for important weights that greatly influence
the outputs, yielding an 'effect of mixed precision' but without physical mixed
precision implementations (which requires specialized hardware accelerators).
Empirically, our method can be implemented by common operands, bringing almost
no memory and computation overhead. We show that our method outperforms a range
of state-of-the-art methods on ImageNet classification and it can be
generalized to more challenging tasks like PASCAL VOC object detection.Comment: Accepted by AAAI202
Diffusion-based Molecule Generation with Informative Prior Bridges
AI-based molecule generation provides a promising approach to a large area of
biomedical sciences and engineering, such as antibody design, hydrolase
engineering, or vaccine development. Because the molecules are governed by
physical laws, a key challenge is to incorporate prior information into the
training procedure to generate high-quality and realistic molecules. We propose
a simple and novel approach to steer the training of diffusion-based generative
models with physical and statistics prior information. This is achieved by
constructing physically informed diffusion bridges, stochastic processes that
guarantee to yield a given observation at the fixed terminal time. We develop a
Lyapunov function based method to construct and determine bridges, and propose
a number of proposals of informative prior bridges for both high-quality
molecule generation and uniformity-promoted 3D point cloud generation. With
comprehensive experiments, we show that our method provides a powerful approach
to the 3D generation task, yielding molecule structures with better quality and
stability scores and more uniformly distributed point clouds of high qualities
Neural Volumetric Mesh Generator
Deep generative models have shown success in generating 3D shapes with
different representations. In this work, we propose Neural Volumetric Mesh
Generator(NVMG) which can generate novel and high-quality volumetric meshes.
Unlike the previous 3D generative model for point cloud, voxel, and implicit
surface, the volumetric mesh representation is a ready-to-use representation in
industry with details on both the surface and interior. Generating this such
highly-structured data thus brings a significant challenge. We first propose a
diffusion-based generative model to tackle this problem by generating voxelized
shapes with close-to-reality outlines and structures. We can simply obtain a
tetrahedral mesh as a template with the voxelized shape. Further, we use a
voxel-conditional neural network to predict the smooth implicit surface
conditioned on the voxels, and progressively project the tetrahedral mesh to
the predicted surface under regularizations. The regularization terms are
carefully designed so that they can (1) get rid of the defects like flipping
and high distortion; (2) force the regularity of the interior and surface
structure during the deformation procedure for a high-quality final mesh. As
shown in the experiments, our pipeline can generate high-quality artifact-free
volumetric and surface meshes from random noise or a reference image without
any post-processing. Compared with the state-of-the-art voxel-to-mesh
deformation method, we show more robustness and better performance when taking
generated voxels as input
Molecular subgroups of adult medulloblastoma: a long-term single-institution study
Background Recent transcriptomic approaches have demonstrated that there are at least 4 distinct subgroups in medulloblastoma (MB); however, survival studies of molecular subgroups in adult MB have been inconclusive because of small sample sizes. The aim of this study is to investigate the molecular subgroups in adult MB and identify their clinical and prognostic implications in a large, single-institution cohort. Methods We determined gene expression profiles for 13 primary adult MBs. Bioinformatics tools were used to establish distinct molecular subgroups based on the most informative genes in the dataset. Immunohistochemistry with subgroup-specific antibodies was then used for validation within an independent cohort of 201 formalin-fixed MB tumors, in conjunction with a systematic analysis of clinical and histological characteristics. Results Three distinct molecular variants of adult MB were identified: the SHH, WNT, and group 4 subgroups. Validation of these subgroups in the 201-tumor cohort by immunohistochemistry identified significant differences in subgroup-specific demographics, histology, and metastatic status. The SHH subgroup accounted for the majority of the tumors (62%), followed by the group 4 subgroup (28%) and the WNT subgroup (10%). Group 4 tumors had significantly worse progression-free and overall survival compared with tumors of the other molecular subtypes. Conclusions We have identified 3 subgroups of adult MB, characterized by distinct expression profiles, clinical features, pathological features, and prognosis. Clinical variables incorporated with molecular subgroup are more significantly informative for predicting adult patient outcome
Effects of Normal Stress and Joint Inclination Angle on Rock Failure Characteristics Under Compression–Shear Conditions
In this study, cement mortar was used to make specimens containing groups of parallel joints with different inclination angles to simulate natural rock mass, and the specimens were subjected to shear tests under different normal stresses. By analyzing the crack propagation path, failure modes, and strength characteristics of these rock specimens, the effects of normal stress and joint inclination angles on the strength and failure characteristics of this type of rock mass were studied. The following conclusions are drawn: 1) when the inclination angles of the joints are 0° and 15°, the changing of the normal stress did not affect the failure mode of the rock mass. The rock mass was mainly in the mode of shear failure, and the increase in the normal stress only increased the spalling area of the rock mass. 2) When the inclination angles of the joints are 30°, 45°, and 60°, with the increasing of the normal stress, the number of those approximately parallel cracks in the specimens increased, the friction marks caused by shearing increased, and the failure mode of the rock mass changed from tension failure to tension–shear composite failure. 3) Under different joint inclination angles, the propagation and penetration paths of cracks generated in the rock mass and the damage mode of the rock mass were different. With an increase in the joint inclination angles, the damage mode of the rock mass gradually changes from shear damage to tensile–shear composite damage and the α and β angles between the through cracks and the vertical direction on the left and right sides of the specimens tended to decrease. 4) The shear resistance of the rock mass was affected by the inclination angle of the joints and the normal pressure. The shear resistance of rock mass was improved due to the increasing of normal stress. Within a certain range, with the increasing of the inclination angles of the joint, the shear resistance of the rock mass tended to decrease first and then to increase
Altered Regional and Circuit Resting-State Activity Associated with Unilateral Hearing Loss
The deprivation of sensory input after hearing damage results in functional reorganization of the brain including cross-modal plasticity in the sensory cortex and changes in cognitive processing. However, it remains unclear whether partial deprivation from unilateral auditory loss (UHL) would similarly affect the neural circuitry of cognitive processes in addition to the functional organization of sensory cortex. Here, we used resting-state functional magnetic resonance imaging to investigate intrinsic activity in 34 participants with UHL from acoustic neuroma in comparison with 22 matched normal controls. In sensory regions, we found decreased regional homogeneity (ReHo) in the bilateral calcarine cortices in UHL. However, there was an increase of ReHo in the right anterior insular cortex (rAI), the key node of cognitive control network (CCN) and multimodal sensory integration, as well as in the left parahippocampal cortex (lPHC), a key node in the default mode network (DMN). Moreover, seed-based resting–state functional connectivity analysis showed an enhanced relationship between rAI and several key regions of the DMN. Meanwhile, lPHC showed more negative relationship with components in the CCN and greater positive relationship in the DMN. Such reorganizations of functional connectivity within the DMN and between the DMN and CCN were confirmed by a graph theory analysis. These results suggest that unilateral sensory input damage not only alters the activity of the sensory areas but also reshapes the regional and circuit functional organization of the cognitive control network
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Basaltic and Solution Reference Materials for Iron, Copper and Zinc Isotope Measurements
Iron, Cu and Zn stable isotope systems are applied in constraining a variety of geochemical and environmental processes. Secondary reference materials have been developed by the Institute of Geology, Chinese Academy of Geological Sciences (CAGS), in collaboration with other participating laboratories, comprising three solutions (CAGS-Fe, CAGS-Cu and CAGS-Zn) and one basalt (CAGS-Basalt). These materials exhibit sufficient homogeneity and stability for application in Fe, Cu and Zn isotopic ratio determinations. Reference values were determined by inter-laboratory analytical comparisons involving up to eight participating laboratories employing MC-ICP-MS techniques, based on the unweighted means of submitted results. Isotopic compositions are reported in per mil notation, based on reference materials IRMM-014 for Fe, NIST SRM 976 for Cu and IRMM-3702 for Zn. Respective reference values of CAGS-Fe, CAGS-Cu and CAGS-Zn solutions are as follows: δ56Fe = 0.83 ± 0.06 and δ57Fe = 1.20 ± 0.12, δ65Cu = 0.57 ± 0.05, and δ66Zn = -0.79 ± 0.12 and δ68Zn = -1.65 ± 0.24, respectively. Those of CAGS-Basalt are δ56Fe = 0.15 ± 0.05, δ57Fe = 0.22 ± 0.05, δ65Cu = 0.12 ± 0.07, δ66Zn = 0.17 ± 0.11, and δ68Zn = 0.34 ± 0.21 (2s)
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