13 research outputs found
Acceleration of stochastic gradient descent with momentum by averaging: finite-sample rates and asymptotic normality
Stochastic gradient descent with momentum (SGDM) has been widely used in many
machine learning and statistical applications. Despite the observed empirical
benefits of SGDM over traditional SGD, the theoretical understanding of the
role of momentum for different learning rates in the optimization process
remains widely open. We analyze the finite-sample convergence rate of SGDM
under the strongly convex settings and show that, with a large batch size, the
mini-batch SGDM converges faster than mini-batch SGD to a neighborhood of the
optimal value. Furthermore, we analyze the Polyak-averaging version of the SGDM
estimator, establish its asymptotic normality, and justify its asymptotic
equivalence to the averaged SGD
BNV-Fusion: Dense 3D Reconstruction using Bi-level Neural Volume Fusion
Dense 3D reconstruction from a stream of depth images is the key to many
mixed reality and robotic applications. Although methods based on Truncated
Signed Distance Function (TSDF) Fusion have advanced the field over the years,
the TSDF volume representation is confronted with striking a balance between
the robustness to noisy measurements and maintaining the level of detail. We
present Bi-level Neural Volume Fusion (BNV-Fusion), which leverages recent
advances in neural implicit representations and neural rendering for dense 3D
reconstruction. In order to incrementally integrate new depth maps into a
global neural implicit representation, we propose a novel bi-level fusion
strategy that considers both efficiency and reconstruction quality by design.
We evaluate the proposed method on multiple datasets quantitatively and
qualitatively, demonstrating a significant improvement over existing methods.Comment: Accepted at CVPR 202
FroDO: From Detections to 3D Objects
Object-oriented maps are important for scene understanding since they jointly
capture geometry and semantics, allow individual instantiation and meaningful
reasoning about objects. We introduce FroDO, a method for accurate 3D
reconstruction of object instances from RGB video that infers object location,
pose and shape in a coarse-to-fine manner. Key to FroDO is to embed object
shapes in a novel learnt space that allows seamless switching between sparse
point cloud and dense DeepSDF decoding. Given an input sequence of localized
RGB frames, FroDO first aggregates 2D detections to instantiate a
category-aware 3D bounding box per object. A shape code is regressed using an
encoder network before optimizing shape and pose further under the learnt shape
priors using sparse and dense shape representations. The optimization uses
multi-view geometric, photometric and silhouette losses. We evaluate on
real-world datasets, including Pix3D, Redwood-OS, and ScanNet, for single-view,
multi-view, and multi-object reconstruction.Comment: To be published in CVPR 2020. The first two authors contributed
equall
Effects of Dietary Selenium on Histopathological Changes and T Cells of Spleen in Broilers Exposed to Aflatoxin B1
Aflatoxin B1 (AFB1), which causes hepatocellular carcinoma and immune-suppression, is commonly found in feedstuffs. To evaluate the ability of selenium (Se) to counteract the deleterious effects of AFB1, two hundred 1-day-old male avian broilers, divided into five groups, were fed with basal diet (control group), 0.3 mg/kg AFB1 (AFB1 group), 0.3 mg/kg AFB1+0.2 mg/kg Se (+Se group I), 0.3 mg/kg AFB1+0.4 mg/kg Se (+Se group II) and 0.3 mg/kg AFB1+0.6 mg/kg Se (+Se group III), respectively. Compared with control group, the relative weight of spleen in the AFB1 group was decreased at 21 days of age. The relative weight of spleen in the three +Se groups was higher than that in the AFB1 group. By pathological observation, the major spleen lesions included congestion in red pulp and vacuoles appeared in the lymphatic nodules and periarterial lymphatic sheath in the AFB1 group. In +Se groups II and III, the incidence of major splenic lesions was decreased. The percentages of CD3+, CD3+CD4+ and CD3+CD8+ T cells in the AFB1 group were lower than those in control group from 7 to 21 days of age, while there was a marked increase in the three +Se groups compared to the AFB1 group. The results indicated that sodium selenite could improve the cellular immune function impaired by AFB1 through increasing the relative weight of spleen and percentages of splenic T cell subsets, and alleviating histopathological spleen damage
Induction of mitochondria-mediated apoptosis and PI3K/Akt/ mTOR-mediated autophagy by aflatoxin B2 in hepatocytes of broilers
The effect of pitch-based carbon fiber microstructure and composition on the formation and growth of SiC whiskers via reaction of such fibers with silicon sources.
The formation and growth of silicon carbide whiskers (SiCw) have been investigated by reaction of silicon sources at 1400 ºC with pitch-based carbon fibers possessing various microstructures. Isotropic and anisotropic pitch-based carbon fibers treated at various temperatures were employed as carbon sources. Silicon sources include silicon powder and a mixture of silicon and silica powder. The reaction of 1000 ºC heat-treated carbon fibers containing a certain content of oxygen with silicon powders is also reported. A reasonable yield of monocrystalline and polycrystalline SiC whiskers can be achieved by the reaction of the isotropic and anisotropic pitch-based carbon fibers treated at 1000 and 2000 ºC with the mixture of silicon and silica. The critical factors for promoting the formation of SiC whiskers are that the carbon sources should possess turbostratically stacked graphite structure and appropriate grain size. The presence of SiO, which originated from the reaction of silicon with silica or with water vapor derived from pyrolysis of carbon fibers, is another necessary condition for formation of SiCw during these reaction processes